WO2016149735A1 - Mesh - Google Patents
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- Publication number
- WO2016149735A1 WO2016149735A1 PCT/AU2016/000098 AU2016000098W WO2016149735A1 WO 2016149735 A1 WO2016149735 A1 WO 2016149735A1 AU 2016000098 W AU2016000098 W AU 2016000098W WO 2016149735 A1 WO2016149735 A1 WO 2016149735A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- fibrous mesh
- mesh
- droplet
- fibrous
- polymer
- Prior art date
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 62
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- 239000003093 cationic surfactant Substances 0.000 claims description 5
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- 229920001600 hydrophobic polymer Polymers 0.000 claims description 4
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- 235000006508 Nelumbo nucifera Nutrition 0.000 description 34
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- XJWSAJYUBXQQDR-UHFFFAOYSA-M dodecyltrimethylammonium bromide Chemical compound [Br-].CCCCCCCCCCCC[N+](C)(C)C XJWSAJYUBXQQDR-UHFFFAOYSA-M 0.000 description 29
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- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
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- 238000004626 scanning electron microscopy Methods 0.000 description 4
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- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 241001314546 Microtis <orchid> Species 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
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- 239000002121 nanofiber Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- HXVNBWAKAOHACI-UHFFFAOYSA-N 2,4-dimethyl-3-pentanone Chemical compound CC(C)C(=O)C(C)C HXVNBWAKAOHACI-UHFFFAOYSA-N 0.000 description 2
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229920001410 Microfiber Polymers 0.000 description 2
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 206010042674 Swelling Diseases 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- SWLVFNYSXGMGBS-UHFFFAOYSA-N ammonium bromide Chemical compound [NH4+].[Br-] SWLVFNYSXGMGBS-UHFFFAOYSA-N 0.000 description 2
- 238000000149 argon plasma sintering Methods 0.000 description 2
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
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- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- WSSJONWNBBTCMG-UHFFFAOYSA-N 2-hydroxybenzoic acid (3,3,5-trimethylcyclohexyl) ester Chemical compound C1C(C)(C)CC(C)CC1OC(=O)C1=CC=CC=C1O WSSJONWNBBTCMG-UHFFFAOYSA-N 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 102100024133 Coiled-coil domain-containing protein 50 Human genes 0.000 description 1
- VGMFHMLQOYWYHN-UHFFFAOYSA-N Compactin Natural products OCC1OC(OC2C(O)C(O)C(CO)OC2Oc3cc(O)c4C(=O)C(=COc4c3)c5ccc(O)c(O)c5)C(O)C(O)C1O VGMFHMLQOYWYHN-UHFFFAOYSA-N 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- SNRUBQQJIBEYMU-UHFFFAOYSA-N Dodecane Natural products CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 1
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- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- 101100299489 Oryza sativa subsp. japonica PTD gene Proteins 0.000 description 1
- 235000014676 Phragmites communis Nutrition 0.000 description 1
- 101000600488 Pinus strobus Putative phosphoglycerate kinase Proteins 0.000 description 1
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- AJLFOPYRIVGYMJ-UHFFFAOYSA-N SJ000287055 Natural products C12C(OC(=O)C(C)CC)CCC=C2C=CC(C)C1CCC1CC(O)CC(=O)O1 AJLFOPYRIVGYMJ-UHFFFAOYSA-N 0.000 description 1
- DHXVGJBLRPWPCS-UHFFFAOYSA-N Tetrahydropyran Chemical compound C1CCOCC1 DHXVGJBLRPWPCS-UHFFFAOYSA-N 0.000 description 1
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- 125000000217 alkyl group Chemical group 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
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- 125000003438 dodecyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
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- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 1
- 238000004442 gravimetric analysis Methods 0.000 description 1
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- 229940079322 interferon Drugs 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000002563 ionic surfactant Substances 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
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- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- AJLFOPYRIVGYMJ-INTXDZFKSA-N mevastatin Chemical compound C([C@H]1[C@@H](C)C=CC2=CCC[C@@H]([C@H]12)OC(=O)[C@@H](C)CC)C[C@@H]1C[C@@H](O)CC(=O)O1 AJLFOPYRIVGYMJ-INTXDZFKSA-N 0.000 description 1
- BOZILQFLQYBIIY-UHFFFAOYSA-N mevastatin hydroxy acid Natural products C1=CC(C)C(CCC(O)CC(O)CC(O)=O)C2C(OC(=O)C(C)CC)CCC=C21 BOZILQFLQYBIIY-UHFFFAOYSA-N 0.000 description 1
- 238000001393 microlithography Methods 0.000 description 1
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- 238000000399 optical microscopy Methods 0.000 description 1
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- 230000002085 persistent effect Effects 0.000 description 1
- RLZZZVKAURTHCP-UHFFFAOYSA-N phenanthrene-3,4-diol Chemical compound C1=CC=C2C3=C(O)C(O)=CC=C3C=CC2=C1 RLZZZVKAURTHCP-UHFFFAOYSA-N 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- BALXUFOVQVENIU-KXNXZCPBSA-N pseudoephedrine hydrochloride Chemical compound [H+].[Cl-].CN[C@@H](C)[C@@H](O)C1=CC=CC=C1 BALXUFOVQVENIU-KXNXZCPBSA-N 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 125000001453 quaternary ammonium group Chemical group 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
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- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L2300/00—Additional constructional details
- B01L2300/16—Surface properties and coatings
- B01L2300/161—Control and use of surface tension forces, e.g. hydrophobic, hydrophilic
- B01L2300/165—Specific details about hydrophobic, oleophobic surfaces
- B01L2300/166—Suprahydrophobic; Ultraphobic; Lotus-effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
- B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
- B01L3/502707—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the manufacture of the container or its components
Definitions
- the "rose petal effect” combines the properties of high adhesion of droplets with ready and substantially quantitative transferability of droplets. These two properties make “rose petal” type surfaces well suited for micromanipulation of droplets, for example for use in icrofluidic devices.
- Microfiuidics enables the characterization, synthesis and processin of functional molecules at a substantially smaller scale, with considerably higher control and less waste than macro- scale processing. This is emphasized by the rapid development and commercialization of a new generation of micro-devices forDNA sequencin and medical analysis.
- a major limitation of current systems is the transfer and handling of single droplets outside a carrier liquid.
- Engineering of nano-Zmicro-structiired surfaees capable of mechanically controlled droplet : pinning and release is a key step toward further reduction of system costs and complexity.
- Droplet manipulation in .microfluidic devices currently relies on the complementary usage of low adhesion lotus leaf-like surfaces and hydrophilic patterns. These coatings are, however, impractical for multi-ste transport and transfer of micro-droplets. Hydrophilic and hydropliobic surfaces result in partial dispersion and contamination of the initial droplet volume while impenetrable lotus-like coatings do not allow sufficient adhesion for ma ipuiatiaii.
- the recently characterized wetting state, naturall observed on rose petals has been proposed as a optimal hiomimetic material property to both impede surface wetting and achieve highly adhesive droplet pinning, making such surfaces highly suitable for use in microfluidic devices.
- the mesh may have one or both of the following two properties:
- the fibrous mesh may have raot-mean-square (RMS) surface roughness of between, about 2 microtis and about 10 microns-.
- RMS raot-mean-square
- Fibres of the mesh may comprise a polymer * They may comprise a polymer composite, in this event, the composite ma comprise nanoparticles, e.g. inorganic nanoparticles, embedded in. the polymer. Suitable inorganic nanoparticles include iron oxide nanoparticles, in particular Fe 3 ( >4 nanoparticles.
- the polymer may he a hydrophobic polymer, e.g. polystyrene. It may be a hydiOphilic polymer. It may be poiycaprolactone.
- the fibrous mesh may comprise fibres -which include microbeads along their length.
- the microbeads may be integral with the fibres *
- the fibres may have on average no more than 1 microbead per 100 microns length.
- the fibrous mesh may comprise a plurality of micropartic les, wherein fibres of the mesh are separated by said microparticles and said microparticles are not integral with the fibres.
- the mesh may have a surface having fro about 3 to about 600 microbeads per mrr ,
- the fibrous mesh may have a thickness of less than about 50 microtis.
- the fibrous mesh may comprise a surfactant.
- the surfactant may be a cationic surfactant.
- a mesh having a static water contact angle of greater than about 150° and an RMS surface roughness of between about 2 microns and about 10 microns, wherein:
- said mesh comprising fibres of a polymer, e.g. polystyrene, which include microbeads along their length, said microbeads being integral with the fibres, wherein said fibres have oil average no more than 1 microbead per 100 microns length.
- a polymer e.g. polystyrene
- a fibrous mesh having a static water contact angle of greater than about 150°, wherein: • a water droplet of about l.Omg adheres to a horizontal underside of said fibrous mesh without detaching therefrom; and
- microbeads • a surface having between about 3 and about 600 microbeads/mm 2 , said microbe-ads having a diameter of between about 1 and about 1 microns and
- a second aspect of the invention there is prov ided a process fo making a fibrous mesh having a static water contact angle of greater than abou t 150°, said process compr ising electiOSpmnmg a liquid polymer composition through a nozzle for sufficient time to form said fibrous mesh .
- the resulting fibrous mesh may have one or both of the following properties:
- the liquid polymer composition may be a solution of a polymer.
- the polymer may be present in the solution at concentration of from about 5 to about 20%w/v.
- the solution may comprise a surfactant
- the surfactant may be present in the liquid polymer composition at a concentration of from about 2 to about 4mg/ml .
- the sufficient time may be sufficient to achieve an RMS surface roughness of between about 2 microns and about 10 microns. It may be sufficient for extrusion of about 0.2 to about 2mg of mesh per cn . It may be about 20 to about 60 minutes. If the concentration of polymer in the liquid polymer composition is about 10 to about 35%w/v then it may be about 20 to about 40 minutes. If the concentration of polymer in the liquid polymer composition is about 15 to about 20% v, then the sufficient time may be about 60 minutes. The sufficient time may be about 0.2 to about ! minute per cm " of substrate.
- the electrospinning may be conducted at a voltage of about 5 to about 2SkV,
- the nozzle ma have an internal diameter of about 0.5 to about 1mm.
- a process for making a fibrous mesh having a static water contact angle of greater man about 1.50 comprising electrospinning a liquid polymer composition comprising about 5 to about 20% of a polymer,, eg. polystyrene, and about 2 to about 4mg/Ml of a surfactant, e.g. a cationic surfactant, through a nozzle having internal diameter of about 0.5 to about 1mm under a voltage of about 5 to about 25kV for about 0.2 to about 1 minute per cm 2 of substrate, so as to form said fibrous mesh, wherein:
- the fibrous mesh of the first aspect may be made by the process of the second aspect.
- the second aspect may provide, or may be capable of providing, the fibrous mesh of the first aspect.
- a process for transferring a liquid droplet from a fibrous mesh according to the first aspect to a second surface comprising:
- a fibrous raesh according to the first aspect, or made b the process of the second aspect, in a microfluidic device.
- Figure 2 Beads, beaded fibers (i.e. partially beaded) and fibrous polystyrene distribution without (a) and with (b) the usage of DTAB under varying electrospinning conditions ' (rel. wt% and effective voltage) with 40 minute deposition time,
- Figure 4 Structural evolution characterization of lotus leaf and rose petal-like wetting states.
- the macro-scale topologies and SEM analysis of heavily beaded (e,e) and partially beaded films (d, f) confirm an increase in bead surface density with increasin deposition time that results in lotus leaf-like super-hydrophobicit .
- Figure 5 Clean and complete transferability of a microdioptet (5 ⁇ ) between (a) two rose-petal interfaces or (b) rose petal interface and hydrophilic substrate (glass), (c) Poor transferability between defective rose petal surface (minoriy beaded film [PS20] made without DTAB) and glass, leaving a residual droplet on the original surface.
- FIG. Schematic description (a) of the droplet transfer mechanism from a nano- mesh coating to a hydrophilic surface and another rose petal coating.
- the nano-mesh release mechanics from rose to rose (b) is explained through computation of the resul tant, force (square) acting on the mesh surface due to Laplace (circles), tension (triangle) and gravitational forces as a function on of the substrate distance .
- Figure 7. White light interferometry derived RMS roughness (a) and film thicknesses (b).
- Figure 10 UY-vis Transmittanee of as-developed Coatings (Beaded; Beaded Fibers and Non-beaded Fibers) at a (400nm) and b ( ⁇ ).
- Figure 1 1 Analysis of droplet holding and transference efficiency - Rose Petal, Lotus Leaf and Non-Superhydrophobic Surfaces, (a) Adhesion strength of droplet-holding samples (h) Droplet transference by Volume (%) for fibrous, niinorly beaded fibers, moderately beaded fibers and heavily beaded fiber surfaces.
- Figure 1.2 Apparatus for measurement of adhesion strength. Description of Embodiments
- the present invention relates to fibrous meshes which exhibit the "rose petal" effec
- These meshes are hydrophobic. They have a high static water contact angle, commonly over about I SO 0 , or over 1 1 , 152, 153, 154 or 155°.
- The may have a static water contact angle of about 150 to about I70 w , or about 150 to 160, 150 to 155, 1.50 to 153, 151 to 155, 152 to 1.55, 152 to 154, 155 to 160 or 160 to 170°, e.g.
- the static water contact angle may be measured by placing approximately 5-6 niicroiitres of water onto the sample surface, which is mai ntained hori zon tal , and measuring the angle of the droplet/surface contac t.
- the term "superhydrophobic" refers to surfaces having a static water contact angle of over I SO 0 , in this test, and in other tests described herein, the water used is deionised water unless otherwise specified.
- the fibrous meshes of the present invention typically have a contact angl hysteresis of from about 45 to about 70°, or from about 50 to 70 or 50 to 60°, e.g. about 45, 50, 55, 0, 65 or 70°.
- Contact angle hysteresis maybe measured by evaporation of a 5 microlitre droplet of water from the surface of the mesh and monitoring of the contact angle over time. Details of a suitable method are described in the experimental section of this specification.
- C3 ⁇ 4 4 A further method of assessing the adhesion is b assessing the maximum droplet size which can adhere to a horizontal underside of the mesh .
- Fibrous meshes according to the present in vention may have a maximum droplet si ze according to this test of at least about 10 mg, or at least about 10.5 , 11, i 1 .5 or 12 ma, or of about 10 to 1.2, 10 to 11, 11 to 12 or 10.5 to 1 1.5 mg, for example about 1.0, 10.5, I I, 1 1.5 or 12 mg, but may be even greater than this.
- the fibrous mesh of the invention may be such that a water droplet of about 10 mg. or about 10.5, 1 L 1 1.5, 12, 12.5, 13, 13.5 or 14mg, adlteres to a horizontal underside thereof without detaching.
- a related measure is the adhesion force of the droplet attached to the horizontal underside of the mesh, hi order to measure this, a second, adliesive, horizontal surface is brought in contact with the droplet, and the force required to detach the droplet from the underside of the mesh is measured., e.g. using a microbalance.
- the adhesion force ma be at least, about 100 microBewtons, or at least about 105 or 110 micronewtons., or from, about 10 to 120 micronewtons, or from about. 1.00 to 11 , 1 1.0 to 120 o 105 to 1 15 micronewtons, e.g. about 100, 105, 1 10, 1 15 or 120 micronewtons.
- a further measure is the tensile strength of the water-mesh interface.
- the tensile strength of the water-mesh interface may be greater than about 100 micronewtons per square millimetre, or greater than about 1 10, 120, 130 or 140 micronewtons per square mi llimetre, or may be from about 100 to about 1.60 micronewtons per square millimetre or from about 100 to 150, 100 to 140, 100 t 130, 120 to 160, 130 to 160, 140 to 160, 120 to 150, 130 to 150 or 1.40 to 150 micronewtons per square .millimetre, e.g.
- the adhesion, of the mesh of the invention may he controllable.
- the rose petal effect (including the adhesion of water droplets to the mesh) ma depend at least in part on various physical parameters of the mesh, including roughness and thickness. These may be varied in a number of ways. Thus for example apply ing a lateral stress (either tensile or compressive) to the mesh ma alter the thickness and surface roughness of the mesh and therefore affect the rose petal properties. This is due to the fact that the meshes have a non-zero Poisson ratio.
- the abovementioned parameters may be altered to the point that the rose petal effect is no longer exhibited and the surface converts to a lotus effect surface (i.e. poor adhesion but still superhydrophobic). This effect may therefore be used to release droplets from the s urface on demand.
- application of an appropriate lateral stress to a lotus effect surface may convert it to rose petal surface, and release of that stress could; then allow the surface to return to a lotus effect nature.
- a similar effect may be generated if magnetic nanoparticles and/or mieroparticles are present in the fibres. In thi s case application of a magnetic: field can cause the mesh to compress, therefore reducing thickness and roughness.
- This may con eniently be used to manipulate a droplet by adhering the drop let to the surface of the mesh in its rose type state and then converting it (by application of a magnetic field, or of lateral stress, either tensile or compressive) into a lotus type state, thereby reducing adhesion and allowing release of the droplet.
- a further aspect of the rose petal effect is, therefore, the abili ty to effecti vely transfer water droplet from the surface.
- the residual water from the droplet that remains on the fibrous mesh ma he less than about 10%, or less than about 5, 2, 1 , 0.5, 0.2 or 0. 1 % of the volume or mass of the original droplet .
- the inventors have surprisingl found that fibrous meshes which exhibit the rose petal effect commonly have an. RMS (root mean square) roughness of about 2 t about 10 microns.
- the EMS roughness may be about 2 to 5, 5 to 10 or 3 to 8 microns, e.g. about 2, 3, 4, 5, 6, 7, 8, 9 o 10 microns.
- a suitable method for monitoring the achievement of the desired rose petal properties may be by monitorbg the RMS roughness.
- electrospirming may simply be performed until the desired MS roughness is- achieved, at which point it may he inferred that the desired rose petal properties are also achieved.
- These may be achieve once there is about 0.2 to about 2mg of mesh per cm 2 , or about 0.2 to 1 , 0.2 to 0.5, 0.5 to 2. I to 2 or 0.8 to 1 Smg/cm 1 , e.g.
- the mesh may have a thickness of less than about 50 microns, or less than about 45, 50, 35 or 30 microns, or of -about 20 to about 50 microns, or about 20 to 40, 20 to 30, 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
- the mesh is commonly a polymeric mesh, i.e. the fibres comprise a polymer. In. some instances the fibres consist essentially of a polymer.
- the im'entors have surprisingl found that there is no requirement for the material, e.g. polymer, from which the mesh is made to be superhydrophobie or even highl hydrophobic. Indeed, it is possible to make fibrous meshes according to the invention from polymers such as polyeaprolactone which are not especially hydrophobic and in some instances from hydrophilic polymers. However hydrophobic polymers such as polystyrene may be used. It is therefore convenient to make the meshes from readily available and inexpensive materials. In some embodiments, therefore, the polymer is not a fluoropo!ymer. in other embodiments it is not a. condensation polymer. In particular, the polymer may not be
- the polymer may have a molecular weight (number average or weight average) of about 10 to about lOOOk a, or about 20 to 1000, 50 to 1000, 100 to 1000, 200 to 1000, 500 to 1000, 10 to 500, 10 to 100, 10 to 50, 50 to 500, 50 to 200, 50 to 100 or 1 0 to 200kDa, e.g. about 10, 0, .30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900 or ⁇ OOOkDa.
- the fibres comprise (or consist essentially of) a polymer composite, i.e. a polymer containing a filler.
- the filler may comprise nanoparticles, whereby the
- nanopartleies do not have a substantial impact on the fibre diameter.
- the nanoparticles may be less than about 5Qnm in diameter, or less than about 40, 30, 20, 10 or Snm., or may be about 5 to about 50ora in diameter, or about 5 to 20, 4 to 10, 10 to 50, 20 to 50 or 10 to 20nra, e.g. about 5, 10, 15, 20,.25, 30, 35, 40, 45 or 50nm in diameter.
- They may be inorganic They may be for example iron oxide (e.g. Fe3 ⁇ 4G iian-opartides), silica, titania, zirconia, alumina, zinc oxide etc. They may be magnetic nanoparticles.
- subst nces are readily available in nanoparticulate form, relatively inexpensive and readily functionalizable. They may be modified, e.g. using fiuoiOsilanes, so as to improve siper rydropliobicity, or may be allowed to increase hi concentration until they confer a more hydrophilic (thus rose-petal) effect on the resulting films. In some instances the presence of such nanoparticles may affect the physical properties of the. fibres, and therefore affect the physical properties (e.g. superhydrophobicity) of the fibrous mesh.
- the inventors have observed that, when other factors are kept constant, an increase in the concentration of polymer in, the eiectrospinning solution results in a progressive change in the morphol ogy of the fibres of the fibrous mesh , Thus when the solution is quite dilu te (e. g. below about 8-10%w/v), the fibres have a large number of microbeads or swellings along their length.
- microbeads ma be around 1-10 microns in diameter and ma be approximately spherical, or may be elongated along the length of the fibre, or may be oblate spherical, or may be ovoid, or may be approximately biconvex discoid shape, or may be toroidal, or may be irregular shaped, or may be some other shape.
- the frequency .of these microbeads along the fibre length decreases, and when a concentration of about 20%w/v is reached there are very few or no microbeads.
- the mean distance between microbeads along tlie fibre may be conveniently tailored by adjusting tli polymer concentration in the electrospmmng solution to anywhere from about 5 microns -upwards, it may be at least about 10, 20, 50, 100 or 200 microns.
- the mean distance between microbeads may be between about 5 and 500 microns, or between. 5 and 200, 5 and 100, 5 and 50, 50 and 500, 100 and 500, 200 and 500, 100 and 200 or 50 and 200 microns, e.g. about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or 500 microns.
- the mesh may have a surface density of the microbeads of between about and about 500 microbeads per mm 2 , or about 3 to 600, 1 to 200, 1 to 100, I to 50, I to 20, 1 to 10, 10 to 500, 50 to 500, 100 to 500, 200 to 500, 50 to 200, 50 to 100 or 100 to 200 microbeads per mm 2 , e g. about L 2, 3, 4, 5, 10, .1.5, 20, 25, 30. 35, 40, 45, 0, 60, 70, 80, 90, 100, 150, 200, 50, 300, 350, 400, 450, 500, 550 or 600 icrobeads per mm 2 . There may in some instances be no microbeads.
- microbeads may serve to space the fibres apart, thereby control ling the . ' RMS roughness of the surface of the fibrous niesh and hence affecting the rose petal effect of that surface.
- These microbeads may be integral wit the fibres. They may comprise (or consist of) the same material as the fibres,
- An alternative wa to affect the spacing of the fibres is to add discrete niicropartieles. As these are added separately, they may be a different substance to the fibres. They may for example be polymeric, or inorganic, e.g. metal oxide, or some other substance. They may be applied by means of a layer b layer construction of the mesh, whereby alternate layers of fibres and microparticles are laved down. .Alternatively they may be included in the electrospinning liquid. In this case they should be made of a substance that does not dissol ve in a solvent used in th electrospinning solution.
- the microparticl es may be spherical (i.e. may be microspheres) or may be polyhedral, irregular or some other shape.
- the surfactant may be an ionic surfactant or may be a non-ionic surfactant. It ma be cationic or anionic. It may be amphoteric, it may be a quaternary ammonium surfactant. It may be an aliphatic (i.e. non-aromatic) quaternary ammonium salt. It may be an
- alkyitrimethylammonium salt The alkyl. group may be CIO to CI 6, or ma be a mixture of various chain lengths, predominantly in the range of 10- 16 (e.g. predominantly or exclusivel CIO, CI 1, CI 2, C13, CI4, CIS or 16).
- a suitable surfactant is a dodecyltriraethylammonium salt (e.g. chloride or bromide).
- the fibrous mesh of the invention may be convenientl made by electrospinning.
- Electrospinning in v olves extrusion of a polymer-containing liquid i.e. art "electrospinning liquid" front a nozzle under an electric potential.
- the electrical potential may be between the nozzle and a substrate on which the substrate is formed.
- the liquid may be a melt of the polymer or may be a solution of the polymer. In the present instance it is more common to use a solution of the polymer.
- the concentration of polymer in the solution is commonly from about 5 to about 25 w/v. It may be about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 20 to 25, 10 to 20, 10 to ⁇ 5 or 15 to 20%, e.g. about 5, 10, 15, 20 or 25%.
- the concentration of polymer in the solution can he used to control the orpology of fibres of the resulting fibrous mesh. This ca in turn control the time required to achiev the desired properties of the mesh.
- a surfactant into the electrospinnmg liqiiid. This is commonly present in a concentration of about 1 to about lOmgaiil, or about 1 to 5, 1 to 2, 2 to 10, 5 to 10, 2 to 6 or 2 to 4mg/ml, e.g. about 1, 2, 3, 4, 5, 6, 7, S s 9 or lOmg/ml.
- the requirement for a surfactant may depend on the nature of the polymer to be electrosptin. It has been found that when the polymer is polystyrene, the presence of
- surfactant is desirable however with othe polymers, particularly amphiphiUc polymers, it may be less important to have a separate surfactant present.
- the sol vent in. the electrosptnntng liqui d may be any solvent capable of dissol ving the polymer.
- solvents suitable for this will vary with the nature of the polymer.
- Suitable solvents in the case of eleetrospimiing of polystyrene include tetrahydrofuran, tetrahydropyran, benzene, toluene, xylene,
- the solvent is preferably a volatile solvent. It may have a boiling point below about 120°C, or less than about 100 or 80 C C.
- the eleetrospmning ma be conducted under a potential of about 5 to about 25 V , or about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 10 to 20, 10 to 15 or 15 to 20V, e.g. about 5, 10, ⁇ 5, 20 or 25 V. it may be conducted at a potential to working distance ratio of about 0.5 to about 5 Went, or about 0.5 to 2, 0.5 to L 1 to 5, 2 to 5, 1 to 2 or 1 to
- the nozzle from which the eleetiospiiining liquid is extruded may be about 0.5 to about mm in internal diameter, or from about 0.5 to 0.8, 0.7 to 1 or 0.6 to O.Smni, e.g. about 0.5, 0.6, 0.7, 0.8, 0,9 or I mm or may be more than 1 or less than 0.5mm in internal diameter, ft may be for example a 1 7G, 18G, 19G, 20G or 21G needle.
- the atmosphere through which the eleetiospiiining is conducted may be maintained at a. temperature of about 5 to about 25°C, or about 5 to 20, 5 to 15, 10 to 25, 15 to 25, 10 to 20 or 15 to 20°C, e,g. at about 5, 6, 7, 8, 9, 10, 1 1 , 1.2, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24 or 25° €. it may be oiaintained at a relati ve humidity of about 30 to 70%, or about 30 to 60, 30 to 50, 40 to 70, 50 to 70 or 40 to 60%, e.g. about 30, 40, 50, 60 or 70%.
- the atmosphere may be air or it may be some other gas, e.g. nitrogen, argon, carbon dioxide etc. or may be a mixture of such gases.
- the distance between the nozzle outlet and the substrate i.e. the working distance, ma be between about 5 to about 20cm, or about 5 to 1 . 5, 5 to 10, 1.0 to 20 or 10 to 15cm, e.g. about 5, i 0, 15 or 20cm, or may be some other distance.
- the flow rate of electrospinnittg solution may be about 0.5 to about 2ml/ ' h, or about 0.5 to I, 1 to 2 or 0.7 to 1 3ml/h, e.g. about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 , 1.2, 1.3, 1.4, 1.5, 1 .6, 1.7, 1.8, 1.9 or 2ml/h.
- the flow rate may be about 25 to about SOOmg polymer per hour, or about 50 to 500, 100 to 500, 200 to 500, 25 to 200, 25 to 100, 25 to 50, 50 to 200, 50 to 100 or 100 to 200mg polymer per hour, e.g. about 25, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450 or 500mg polymer per hour. It may be about 0.05 to about 2 rag polymer per hour pe square cm of substrate, or about 0.1. to 2, 0.5 to 2. 3 to 2, 0.05 to 1 , 0.05 to 0.5, 0.05 to 0.1 , 0.1 to: 1 , 0.1 t 0.5 or 0.5 t 3 rag per hour per square cm of substrate, e.g.
- the surface characteristics of the fibrous mesh produced by the above method may vary with the time of extrusion. Therefore in order to obtain the desired properties, it may b necessary to continue the electrospinnmg for a specified time but no longer. It has been observed that as electrospmrmig progresses, the fibrous mesh is initially not superliydrophobic (i.e. does not have a static water contact angle of 350° or more). After sufficient time, the desired rose petal characteristics (superhydiOphobicity, adhesiveness to droplets and clean transfer of droplets) are achieved, if electrospinning is continued, the surface adopts the lotus leaf characteristics whereby it. is snperhydrophobtc but does not adhere adequately to droplets. The time required i order to achieve rose petal characteristics but not progress to lotus characteristics may vary depending on the electiOspinning parameters, the nature of the
- the time of extrusion is commonly about .15 to about 60 minutes, or about 1 to 30, 30 to 60 or 20 t 40 minutes, e.g. about 1.5, 20, 25, 30, 35, 40, 45, 50, 55 or 60 minuter It may be no more than about 70 minutes. This time ma depend on multiple factors, including the area over which the mesh is formed, the concentration of polymer in the extruded solution etc.
- the time pf extrusion may be sufficient to achieve the rose petal type surface, and ma be insufficient to achieve a lotus leaf type surface, it may be sufficient to achieve a
- simerhydrophobie surface and insufficient to achieve a lotus leaf type surface it may be sufficient to achieve an RMS surface roughness (as measured for example by AFM or by white light interferometry) of about 2 to about i 0 microns, ft may be sufficient to achieve extrusion of about 0.01 to about 2mg of mesh per cm 2 . It may be for about 0.05 to about 0.2 minute per cm 2 of substrate., or about 0.05 to 0.1 , 0.1 to 0.2, 0.07 to 0.13 or 0.1 to 0.13 minute per cm 2 of substrate, e.g.
- a film thickness of about 20 to about 50 mi crons, or about 20 to 40, 20 to 30 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
- the inventors have thus found a process to achieve a highly adhesive rose petal effect by means of a tunable hierarchical morphology.
- mats or meshes of polystyrene nanoiibers/beads were synthesized by eleCttOspinning/s iaying into self-assembled hierarchical films for application as sticky super-hydrophobic coatings.
- Morphological modification leading to the rose petal effect was achieved, in a specific example, using dodecyl trimethyl ammonium bromide (a cationic surfactant).
- Coatings were developed through the elimination of beaded films (known for low-adhesion lotus leaf supet-hydinophobicit ), transiting wettin characteristics fro low-adhesion lotus-leaf ' super-hydrophobicity to highly adhesive rose-petal super*hydrophobieity. It is hypothesised that the microbeads along the fibres represent a transition zone between electrospinning and electrospraying. Thu it is thought that more dilute solutions of polymer have poorer cohesion and hence are more likely to form droplets, leading to beads rather than cohesive strands.
- electrospinniti a moderately dilute polymer solution, in particular when a suitable surfactant is present in the solution, produces a fibrous mesh in which swellings, or microbeads, are present along the fibres. They have further observed that an increase in the polymer concentration in the liquid polymer compositio from which the mesh is eSectrospun gives rise to a decrease in the frequency of microbeads along the fibres. These microbeads appear to have aft effect on the physics of the surface of the mesh. It is hypothesised that a certain range of surfac roughness is required in order to achieve the desired "rose petal" effect. This roughness appears to be from about 2 to about 10 microns RMS. The surface roughness may for example be measured using .white light interterometry or using atomic force microscopy.
- the microbeads along the fibre length serve to space the fibres away from each othe in order to achieve the desired surface roughness, lit the absence of the microbeads, it is necessar to continue the electrospinmng for a longer time, so as to achieve a greater tliickness, so that the fibres themselves serve to space fibres from each other and achieve the desired roughness.
- eiectrospinning is continued for too long, it is thought that the fibres, and microbeads, fill in the troughs so as to reduce the surface roughness arid therefore destroy the rose petal effect. Therefore it is important to achieve the correct balance between polymer concentration and time, and possibly also other parameters such as voltage, working distance, flow rate, humidity etc. so as to achieve the desired effect.
- the static CA eonresponds to a unique equilibrium positio of the solid- liquid-air contact line (triple line).
- Cm a rough surface, equilibriums exist over a range of CA,
- the receding C A, 8 . generally represents the minimum CA, while the advancing CA, 8 S d , will represent the maximum CA,
- the difference between these measurements is termed as the contact angle hysteresis (CAH),
- the Cassie Impregnating mechanism does not require air pockets between the highest asperities of the surface (Cassie), or full liquid penetration between micro-stoicturai features (Wenzel). Instead, this regime involves an intermediate state of wetting, where water droplets penetrate one or more levels of the micro- scale features:. Through these multi-level, penetrations, suc surfaces experience high CAH and high droplet adhesion. As such, the morphological surface structure of surfaces (pitch and density of micro-nano-structiires) is known to be vital in developing surfaces with varied wettin performance (super-hydiOphohicity with high or low adhesion).
- Fibrous films (PTD20, Figure ic) consisted of a vertically stacked network of mesoporous fiber layers. They featured the smallest ( ⁇ 100 nm) surface pore size distribution (Figure I f) and the largest variation in fiber diameters (Figure l c) with an average of 5.0 ⁇ 0.7 ⁇ .
- the heavily beaded films (PTDS3, Figure la) were made of a dense assembly (ca. 650 beads / mm 2 ) of relatively small micro-beads of 7.1 * 0.2 ⁇ in diameter occasionally separated by very thin iianofibers of 176 ⁇ 3 alii in diameter.
- PTD5 was composed primari ly of beads, with diameters of 8.6 ⁇ 0.5 ⁇ , resembling hemispheres.
- PS2H 2.5 Minorly beaded films & [00075]
- a third distinctive morphology having a unique cross-sectional structure was achieved by controlled beading during electrospinning of fibrous films (PTDI , Figure l b). These were mostly composed of non-porous sub-micrometer ' . fibers of 41.8 ⁇ 38 urn ( Figure lb/e) and few large beads (ca. 160 beads / mm " ) having an average diameter of .13.5 ⁇ 0.6 pm. The latter had a similar surface pore, structure as that observed on the heavily beaded coatings with slightly large pore diameters distributed between 200 and 400 run (Figure le).
- PTDI 5 appears distinctively similar to PTDIO, consisting of beads and fibers, but with diameters of 1 1.8 ⁇ 0.5 pm and 739 ⁇ 31 nm respectively (data not shown).
- a key feature of these partially beaded films was the self- assembly of a stacked structure of nano/micro-iibrous layers vertically spaced by the large micro-beads.
- This three-dimensional fiber layer distribution resulted in a nano-mesh structure with inter-Fiber pores ranging from a few to tens of micrometers.
- the sizes of the inter- fiber pores may be easily determined using rough measurement on SE data. It should be noted that this is only an approximate measurement due to oddly shaped pores formed by intercrossing fibers. The average sizes were around 5 ⁇ with a standard deviation of .about ' 2 pm. However, fiber to .fiber distance, which is equated to pore size, could range up to about lOpm.
- PS 5 was composed primarily of beads, albeit at larger diameters than PTD5; PS20 was of a simila morphological construct as PTDI 0 and PTDI 5; PSl 5 was highl comparable with PTD8; while PTD20 remains to be uniquely fibrous and not duplicated In the films made without DTAB.
- the pores within the microbe-ads and or the fibres of the meshes of the present invention may be from about 20 to about 200nm, or about 20 to 100, 20 to 50, 50 to 200, 100 to 200 or 50 to lOOnm, e.g. about 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180 or 200nm. These may be measured for example by nitrogen adsorption or BET (specific surface area analysis by nitrogen adsorption).
- the rnicrobeads themselves may be from about 1 to about 2 microns in diameter, or about 1 to 10, 1 to 5, I to 2, 2 to 20, 5 to 20, 30 to 20 or 5 to lOmicrons, e.g.
- the fibres may be about 0.1 to about 1.0 microns in diameter, or about 0.5 to. 10, 1 to 1 , 5 to 10, 0.1 to S. ⁇ O.I to 2, 0.1 to 1, 0.5 to 5 or 1 to 5 microns, e.g. about OJ , 0.2, 0.3, 0.4, 0.5, 3 , 1.5, 23, 2.5, 3, 3.5, 4, 4.5- 5, 6, 7, 8, 9 or 10 microns.
- the interfibre pores may be from about 3 to about 10 microns, or about 1 to 5, i to 2, 2 to 10, 5 to 1 or 3 to 8 microns, e.g.
- the transmittance decreased linearly with increasing deposition time indicating uniform, fiber formation and consistent structural properties within the whole range investigated.
- the optical properties of the partially beaded films (Figure Ih, triangles) closel followed that of the fibrous morphology with ca. 7% less transmittance. This is mainly attributed to the light scattering from the few micro-sized beads distributed in the nano-mesh structure ( Figure lb).
- Further increasing the deposition time considerably increased the optical losses through these films, resulting in more than 15% less transmittance than fibrous films at 50 and 60 min ( Figure Ik, ' triangles and circles). This suggests that above 40 minutes deposition time, the beads reach sufficient surface density to scatter a. significant fraction of the incoming light.
- the heavily beaded film were the least transparent (Figure Ih, squares) with up to 15-50% lower transmittance than purely fibrous films. This is attributed to the high density of light-scattering beaded roicrostructures. effectively coating the substrate surface . Within minor variations, the structural properties of this morphology did not undergo substantial distinctions with increasing deposition time.
- the meshes of the invention may therefore have a transmittance at 600nm of at least about 70%, or at least about 75%, or of about 70 to 90%, 70 to 85%, 75 to 90% or 75 to 85%, e.g. about 70, 75, 80, 85 or 90%.
- Polystyrene nauostructures prepanea ⁇ - ifh or without DTAB were farther investigated with respect to th resulting morphology ( Figure 2).
- nano-mesh thickness is required to completely avoid wate contact with the underlying substrate while exceedingly high film, thicknesses result in high bead density( Jow pitch distances), effectively leading to wetting similar to that observed for the heavil beaded morphology .
- the nano-fibrous mesh was found to serve as a penetrable layer for micro-droplet adhesion.
- the nano-mesh films experienced transition to lotuslike behavior wit sliding angles of 40 - 50°. This is attributed to the increase in surface roughness and bead density (Figure 4d) with increasing deposition time that results in a hardly penetrable small-pore layer.
- the contact angle hysteresis lor the lotus surface (PTD8) was found to be around 42°, qomparable- to previous studies classified for low adhesive surfaces.
- the nan super Tiydropfiobie surface exhibited a contact angle hysteresis of 77.7°, representing a fairly distinctive difference from the super- hydrophobic sticky/slippery surfaces (Figure 9).
- the heavily beaded fiber surfaces and pure fibrous surfaces possessed rose petal qualities at higher deposition times (60 minute). Contrary to the transitional behavior of fibrous surfaces, the heavily beaded fibrous surfaces transited from the lotus leaf effect to the rose-petal effect. Ironically, this effect could also be analyzed via the film thickness, albeit in an alternate sense. As heavily beaded fibrous surfaces are .formed on a spinning drum, less winding of continuous fibers occurs. Instead, scatters of heavily beaded material are formed, and become electrostatically drawn onto the spinning drum. This forms a discontinuous surface (which gives the original super-hydrophohtctty).
- microfluidics Given the ease of possible modifications that nanofibrous surfaces could undergo, they may even hold the potential for actuated droplet control .
- micro-reactors in line with other techniques, furthers tire efficiency of lab- on-chip or bio ssay technologies.
- Arrays of ' micro-reactors wil also provide high throughput combinatorial studies, with extensive implications i fields related to biology, chemistry and engineering.
- DMA sequencing also belongs to a sub-set of micro-reactor development, where sealed domains and channels of reaction zones are used i immobilizing and subsequently analysing DMA templates.
- sealed domains and channels of reaction zones are used i immobilizing and subsequently analysing DMA templates.
- the use of an unsealed, but sterile rose-petal like environment provides much greater versatility towards these analytical techniques.
- the contact angle hysteresis (C AH) was measured based on the drop-out advancing contact angles ( ⁇ 3 ⁇ 4 ⁇ : , 0 to 5 " ,uL, 3 readings) and evaporative receding angles ( ⁇ ,3 ⁇ 4), of which the latter utilizes natural evaporation of a drop of deionized water (5 ⁇ _, 3 readings).
- the evaporative procedure for obtaining receding contact angles was chosen due to its greater sensitivity in contrast, to other means, such as the drop-in technique, a no interference from the deposition needle is present during wiihdmwal.
- the time of evaporation was approximately 70- 80 minutes at 20-25 3 ⁇ 4 C and a relative humidit of 40-50 %.
- Dynamic and static images were recorded using a KSV CA 2.00 contact angle goniomete (Finland) with a. heliopan BS43 camera (Japan).
- the CA, SA and CAB were computed by a commercially available (CAM2008) program.
- ⁇ is surface tension (0,072 N/m)
- ⁇ represents the contact angle (measured on the right and ⁇ eft of droplet accounting to instances of asymmetry)
- f denotes the surface roughness
- m ⁇ g is the gravitational force on the droplet
- F is the net force centered on the top plate.
- Surface roughness (f) of 1 was used as per the standardized formulae. The actual f was computed based on 2 inverted droplets at equilibrium via equation 3 at 1.05 ⁇ 0.01. An average contact area. (JTD ) of 0,90 ⁇ 0.03 mm " was used up to the beginning of significant droplet detachment. Thereafter * the contact area was measured for each frame v rying from an initial 1 ,30 mnr to
- Align stands using a spirit level to ensure horizontal alignment.
- a 5-6 ⁇ drop is placed onto the surface using a 25G needle. This ensures a pinning diameter of the droplet of about 1mm. Excessive droplet size may encourage a larger pinning diameter/ vertical penetration, leading to false adhesion values.
- Steps 2-8 are repeated for 3 times and an average is taken as the maximum adhesion force.
- Morphological optimizations were first conducted using a light microscope (Nikon Eclipse E200®, TV lens 0.55x DS) on coated glass substrates. These optimization experiments were conducted twice to ensure repeatability (under controlled, environments). The 5 distinct morphological distinctions were noted based on observin the prevalence of beads on an area of about 0.31 mm" (480 ⁇ x 640 ⁇ ), Table I. Selected samples were also later analyzed via scanning electron microscopy and white light inter ferometry.
- U V-vis analysis was conducted using a mieroplate reader (Teean 200 PRO®, Switzerland) from 300-800 nm wit 10 scans per cycle.
- Fourier transform infrared spectroscopy (FTIR-AT , Broker-Alpha, U.S-A) was performed (16 scans ftom 400 to 4000cm "1 ) on samples to verify possible chemical modifications.
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Abstract
The invention relates to a fibrous mesh and to processes for making same. The fibrous mesh has a static water contact angle of greater than about 150°. A water droplet of about 10mg can adhere to a horizontal underside of the fibrous mesh without detaching from it and transfer of such a droplet from the underside of the fibrous mesh to a second surface occurs such that essentially none of the water of tire droplet remains adhered to the fibrous mesh.
Description
MESH
Field
[0001 ] This application deals with surfaces exhibiting the "rose petal"" effect and for processes for making them.
Priority
[0002] This application claims priority from Australian Provisional Patent Application no. 2015901055. the entire contents of which are incorporated herein by cross-reference.
Background
[0003] Super-hydrephobicity has been a fundamental, cornerstone of surface phenomena since the advent of hiomimetic research. The physics behind the behavior of water droplets on. such surfaces has captured the attention of scientists and engineers alike. The research efforts directed towards synthetic fiinctional soper-hydrQphobic surfaces are extremely diverse, invol ving specializations that include microfluidics, anti-corrosion, anti-icing, chemical, separation processes and even self-cleaning fabrics.
[0004] .In nature, the most renowned example of super-hydtophobicity belongs to that of Nehmho, the lotus plant from which the "lotus leaf effect"" is named, albeit th presence of a multi tude of biological v ari an ts. More recently, asa, the rose was also found to exhibit super- hydrophobic behaviors. However, unlike the low adhesion super-hydrophohicity demonstrated b the lotus leaf, the rose petal possesses highly adhesive siiper-hydrophobic properties (the "rose petal effect"). While the biological function for th rose is still not fully understood, the potential of such synthetic surfaces may provide perfect functional analogs in applications Involving microfiuklic devices and !ab-on-a-chi technologies.
[0005] The "rose petal effect" combines the properties of high adhesion of droplets with ready and substantially quantitative transferability of droplets. These two properties make "rose petal" type surfaces well suited for micromanipulation of droplets, for example for use in icrofluidic devices.
[0006] Microfiuidics enables the characterization, synthesis and processin of functional molecules at a substantially smaller scale, with considerably higher control and less waste than macro- scale processing. This is emphasized by the rapid development and commercialization of a new generation of micro-devices forDNA sequencin and medical analysis.
[0007] A major limitation of current systems is the transfer and handling of single droplets outside a carrier liquid. Engineering of nano-Zmicro-structiired surfaees capable of mechanically controlled droplet : pinning and release is a key step toward further reduction of system costs and complexity. Droplet manipulation in .microfluidic devices currently relies on the complementary usage of low adhesion lotus leaf-like surfaces and hydrophilic patterns. These coatings are, however, impractical for multi-ste transport and transfer of micro-droplets. Hydrophilic and hydropliobic surfaces result in partial dispersion and contamination of the initial droplet volume while impenetrable lotus-like coatings do not allow sufficient adhesion for ma ipuiatiaii. The recently characterized wetting state, naturall observed on rose petals, has been proposed as a optimal hiomimetic material property to both impede surface wetting and achieve highly adhesive droplet pinning, making such surfaces highly suitable for use in microfluidic devices.
[0008] There is therefore need for a sim le, preferably scalable, process for making surfaces exhibiting tire rose petal effect, i.e. for making superhydropbobic surfaces that are highly adhesive but which exhibit-efficient, droplet transfer with minimal retention of the transferred liquid.
Summary of invention
[0009] In a first aspect of the invention there is prov ided fibrous mesh having a static water contact angle of greate than about 150°. The mesh may have one or both of the following two properties:
• a water droplet of about lOmg adheres to a horizontal underside of said fibrous mesh without detachin therefrom; and
• transfer of said droplet from said underside to a second surface occurs such that
essentially none of the water of said droplet remains adhered to said fibrous mesh.
[00010] The following options may be used in conjunction with the first aspect, either
individually or in any suitable combination.
[0001 1] The fibrous mesh, may have raot-mean-square (RMS) surface roughness of between, about 2 microtis and about 10 microns-.
[00012] Fibres of the mesh may comprise a polymer* They may comprise a polymer composite, in this event, the composite ma comprise nanoparticles, e.g. inorganic nanoparticles, embedded in. the polymer. Suitable inorganic nanoparticles include iron oxide nanoparticles, in particular Fe3 (>4 nanoparticles. The polymer may he a hydrophobic polymer, e.g. polystyrene. It may be a hydiOphilic polymer. It may be poiycaprolactone.
[00013] The fibrous mesh may comprise fibres -which include microbeads along their length. The microbeads may be integral with the fibres* The fibres may have on average no more than 1 microbead per 100 microns length. Alternatively, or additionally the fibrous mesh may comprise a plurality of micropartic les, wherein fibres of the mesh are separated by said microparticles and said microparticles are not integral with the fibres. The mesh may have a surface having fro about 3 to about 600 microbeads per mrr ,
[00014] The fibrous mesh may have a thickness of less than about 50 microtis.
[00015] The fibrous mesh may comprise a surfactant. The surfactant ma be a cationic surfactant.
[00016] In an embodiment there is provided a mesh having a static water contact angle of greater than about 150° and an RMS surface roughness of between about 2 microns and about 10 microns, wherein:
* a water■droplet of at least I Qmg adheres to a horizontal 'underside of said fibrous mesh without detaching therefrom; and
* transfer of said droplet from said underside to a second surface occurs such that
essentially none of the water of said droplet remains adhered to said fibrous mesh, said mesh comprising fibres of a polymer, e.g. polystyrene, which include microbeads along their length, said microbeads being integral with the fibres, wherein said fibres have oil average no more than 1 microbead per 100 microns length.
[00017] In another embodiment there is provided a fibrous mesh having a static water contact angle of greater than about 150°, wherein:
• a water droplet of about l.Omg adheres to a horizontal underside of said fibrous mesh without detaching therefrom; and
• transfer of sai d dropl et from said underside to a second surface occurs such that
essentially none of the water of said droplet remains adhered to said fibrous mesh said mesh having:
• a surface having between about 3 and about 600 microbeads/mm2, said microbe-ads having a diameter of between about 1 and about 1 microns and
• a mi ckness of less than about 50 microns ; and
• aft RMS roughness of between about 2 and about 10 microns.
[00018] In. a second aspect of the invention there is prov ided a process fo making a fibrous mesh having a static water contact angle of greater than abou t 150°, said process compr ising electiOSpmnmg a liquid polymer composition through a nozzle for sufficient time to form said fibrous mesh . The resulting fibrous mesh may have one or both of the following properties:
• a water drop let of at least IQmg adheres to a horizontal underside of said fi br ous mesh without detaching therefrom; and
• transfer o f said droplet from sai d underside to a second surface occurs such that
essentially none o the water of said droplet remains adhered to said fibrous mesh,
[00019] The following options may be used in conjunction with the second aspect, either individually or in any suitable combination.
[00020] The liquid polymer composition may be a solution of a polymer. The polymer ma be present in the solution at concentration of from about 5 to about 20%w/v.
[00021] The solution may comprise a surfactant The surfactant may be present in the liquid polymer composition at a concentration of from about 2 to about 4mg/ml .
[00022] The sufficient time may be sufficient to achieve an RMS surface roughness of between about 2 microns and about 10 microns. It may be sufficient for extrusion of about 0.2 to about 2mg of mesh per cn . It may be about 20 to about 60 minutes. If the concentration of polymer in the liquid polymer composition is about 10 to about 35%w/v then it may be about 20 to about 40 minutes. If the concentration of polymer in the liquid polymer composition is about 15 to
about 20% v, then the sufficient time may be about 60 minutes. The sufficient time may be about 0.2 to about ! minute per cm" of substrate.
[00023] The electrospinning may be conducted at a voltage of about 5 to about 2SkV,
[00024] The nozzle ma have an internal diameter of about 0.5 to about 1mm.
[00025] In an embodiment there is provided a process for making a fibrous mesh having a static water contact angle of greater man about 1.50 said process comprising electrospinning a liquid polymer composition comprising about 5 to about 20% of a polymer,, eg. polystyrene, and about 2 to about 4mg/Ml of a surfactant, e.g. a cationic surfactant, through a nozzle having internal diameter of about 0.5 to about 1mm under a voltage of about 5 to about 25kV for about 0.2 to about 1 minute per cm2 of substrate, so as to form said fibrous mesh, wherein:
• a. water droplet of at least ! Omg adheres to a horizon tal underside of said fibrous mesh without detaching therefrom; and
• transfer o f said drop let from said under si de to a second surface occurs such that
essentially none of the water of said droplet remains adhered to said fibrous mesh,
[00026] The fibrous mesh of the first aspect may be made by the process of the second aspect. The second aspect may provide, or may be capable of providing, the fibrous mesh of the first aspect.
[00027] In a third aspect of the invention there is provided a process for transferring a liquid droplet from a fibrous mesh according to the first aspect to a second surface, said process comprising:
• bringing said second surface in contact with said liquid drop; and
• withdrawing the second surface from the fibrous mesh so as to detach said liquid drop from the fibrous mesh;
wherein substantially no liquid from the liquid drop remains on the fibrous mesh following said detaching.
[00028] In a fourth aspect of the invention there is provided use of a fibrous raesh according to the first aspect, or made b the process of the second aspect, in a microfluidic device.
Brief Description of Drawings
[00029] Figure t. Structural (20 μιη scale a to c ; 200 nm scale, d to f; d to f correspond to a to c respectively at higher magnification)., chemical f g) and optical (It) characterization at 600 nm of three key polystyrene (PS) nano mtcro-morphologies at 40 minutes deposition time having distinctive functional wetting regimes. In. (h) rose-petal, effect samples are shown as filled symbols. Heavily beaded films (a and d) lead predominantly to lotus leaf-effect, partially beaded (b and e) to rose petal-effect, and fibrous (e and f to hydrophobic/hydrophilic. Fourier
Transferal Infrare Spectroscopy (g) of all morphologies (top trace, polystyreiie-DTAB), indicated that the surface composition was consistent, with pure polystyrene (PS, middle trace).
[00030] Figure 2. Beads, beaded fibers (i.e. partially beaded) and fibrous polystyrene distribution without (a) and with (b) the usage of DTAB under varying electrospinning conditions' (rel. wt% and effective voltage) with 40 minute deposition time,
[00031] Figure 3. Static water contact (sessile drop) test on as-synthesized surfaces - polystyrene was spun at conditions with (a) modified with DTAB and (b) unmodified with DTAB. Five contact angle readings were taken for each data point.
[00032] Figure 4. Structural evolution characterization of lotus leaf and rose petal-like wetting states. The RM S roughness (a) and film thickness (b) of heavily and partially beaded films made with DTAB was measured as a function of depositi on time by wh ite light interferon! etry (WL-I) and critically compared to the resulting wetting properties. .In (a) and (b) rose-petal effect samples are shown as filled symbols. The macro-scale topologies and SEM analysis of heavily beaded (e,e) and partially beaded films (d, f) confirm an increase in bead surface density with increasin deposition time that results in lotus leaf-like super-hydrophobicit .
[00033] Figure 5. Clean and complete transferability of a microdioptet (5μί) between (a) two rose-petal interfaces or (b) rose petal interface and hydrophilic substrate (glass), (c) Poor transferability between defective rose petal surface (minoriy beaded film [PS20] made without DTAB) and glass, leaving a residual droplet on the original surface.
[00034] Figure 6. Schematic description (a) of the droplet transfer mechanism from a nano- mesh coating to a hydrophilic surface and another rose petal coating. The nano-mesh release mechanics from rose to rose (b) is explained through computation of the resul tant, force (square) acting on the mesh surface due to Laplace (circles), tension (triangle) and gravitational forces as a functi on of the substrate distance .
[00035] Figure 7. White light interferometry derived RMS roughness (a) and film thicknesses (b).
[00036] Figure , Differing evaporative mechanics (contact angle hysteresis) for surfaces with different adhesive properties.
[00037] Figure 9, Contact angle hysteresis measurements for receding angles via the
e aporati on technique .
[00038] Figure 10. UY-vis Transmittanee of as-developed Coatings (Beaded; Beaded Fibers and Non-beaded Fibers) at a (400nm) and b (όθθηηι).
[00039] Figure 1 1 , Analysis of droplet holding and transference efficiency - Rose Petal, Lotus Leaf and Non-Superhydrophobic Surfaces, (a) Adhesion strength of droplet-holding samples (h) Droplet transference by Volume (%) for fibrous, niinorly beaded fibers, moderately beaded fibers and heavily beaded fiber surfaces.
[00040] Figure 1.2. Apparatus for measurement of adhesion strength. Description of Embodiments
[00041] The present invention relates to fibrous meshes which exhibit the "rose petal" effec These meshes are hydrophobic. They have a high static water contact angle, commonly over about I SO0, or over 1 1 , 152, 153, 154 or 155°. The may have a static water contact angle of about 150 to about I70w, or about 150 to 160, 150 to 155, 1.50 to 153, 151 to 155, 152 to 1.55, 152 to 154, 155 to 160 or 160 to 170°, e.g. about 150, 150.5, 15 L 351.5, 152, 152.5, 153, 153.5, 154, 154.5, 155, 156, 157, 158, 159, 160, 165 or 170°. The static water contact angle may be measured by placing approximately 5-6 niicroiitres of water onto the sample surface, which is mai ntained hori zon tal , and measuring the angle of the droplet/surface contac t. In the con text of the present invention, the term "superhydrophobic" refers to surfaces having a static water contact angle of over I SO0 , in this test, and in other tests described herein, the water used is deionised water unless otherwise specified.
[00042] I conjunction with the hydrophohicity, the rose petal effect requires good adhesion of the droplet. There are several ways to measure this. One way is to measure the sliding angle. In
this test, an approximatel 5 micro! ter drop of water is placed on the surface, whi ch is i nitially borizoiital. The surface is then slowly tilted until the drop rolls off. The angle at which this occurs is the sliding angle. Th fibrous meshes of the present invention may have no measurable sliding angle, as they can hold droplets even while the base substrate is inverted. However, lotus effect surfaces, although similarl hydrophobic, may have measurable sliding angle, indicating their lack of adhesion to aqueous droplets.
[00043] Another measure of the adhesion is the contact angle hysteresis. Surfaces having low adhesio also show low co tact angle hysteresis. However those samples showing very high contact angle hysteresis, although having good adhesion, are typically not superhydrophobic and do not exhibit the desired propert of essentially quanti tative droplet transfer from the mesh. The fibrous meshes of the present invention typically have a contact angl hysteresis of from about 45 to about 70°, or from about 50 to 70 or 50 to 60°, e.g. about 45, 50, 55, 0, 65 or 70°. Contact angle hysteresis maybe measured by evaporation of a 5 microlitre droplet of water from the surface of the mesh and monitoring of the contact angle over time. Details of a suitable method are described in the experimental section of this specification. C¾ 4 A further method of assessing the adhesion is b assessing the maximum droplet size which can adhere to a horizontal underside of the mesh . Fibrous meshes according to the present in vention may have a maximum droplet si ze according to this test of at least about 10 mg, or at least about 10.5 , 11, i 1 .5 or 12 ma, or of about 10 to 1.2, 10 to 11, 11 to 12 or 10.5 to 1 1.5 mg, for example about 1.0, 10.5, I I, 1 1.5 or 12 mg, but may be even greater than this. Thus the fibrous mesh of the invention may be such that a water droplet of about 10 mg. or about 10.5, 1 L 1 1.5, 12, 12.5, 13, 13.5 or 14mg, adlteres to a horizontal underside thereof without detaching. A related measure is the adhesion force of the droplet attached to the horizontal underside of the mesh, hi order to measure this, a second, adliesive, horizontal surface is brought in contact with the droplet, and the force required to detach the droplet from the underside of the mesh is measured., e.g. using a microbalance. For fibrous meshes according to the present invention, the adhesion force ma be at least, about 100 microBewtons, or at least about 105 or 110 micronewtons., or from, about 10 to 120 micronewtons, or from about. 1.00 to 11 , 1 1.0 to 120 o 105 to 1 15 micronewtons, e.g. about 100, 105, 1 10, 1 15 or 120 micronewtons. A further measure is the tensile strength of the water-mesh interface. For fibrous meshes according to the pres ent invention, the tensile strength of the water-mesh interface may be greater than about 100 micronewtons per square millimetre, or greater than about 1 10, 120, 130 or 140 micronewtons
per square mi llimetre, or may be from about 100 to about 1.60 micronewtons per square millimetre or from about 100 to 150, 100 to 140, 100 t 130, 120 to 160, 130 to 160, 140 to 160, 120 to 150, 130 to 150 or 1.40 to 150 micronewtons per square .millimetre, e.g. about 100, 105, 1 10, 110, 1 15, 120, 125, 130, 135, 140, 145, 150, 1.55 or 160 micronewtons per square millimetre. SUf s »<s ®$4m®Mw M m * i$m-MM<i ®$ teft]
[00045] The inventors have found that the adhesion, of the mesh of the invention may he controllable. As noted elsewhere, the rose petal effect (including the adhesion of water droplets to the mesh) ma depend at least in part on various physical parameters of the mesh, including roughness and thickness. These may be varied in a number of ways. Thus for example apply ing a lateral stress (either tensile or compressive) to the mesh ma alter the thickness and surface roughness of the mesh and therefore affect the rose petal properties. This is due to the fact that the meshes have a non-zero Poisson ratio. I particular, the abovementioned parameters may be altered to the point that the rose petal effect is no longer exhibited and the surface converts to a lotus effect surface (i.e. poor adhesion but still superhydrophobic). This effect may therefore be used to release droplets from the s urface on demand. Similarly, application of an appropriate lateral stress to a lotus effect, surface may convert it to rose petal surface, and release of that stress could; then allow the surface to return to a lotus effect nature. A similar effect may be generated if magnetic nanoparticles and/or mieroparticles are present in the fibres. In thi s case application of a magnetic: field can cause the mesh to compress, therefore reducing thickness and roughness. This can therefore under appropriate conditions cause a lotus type surface to convert to a rose type surface or a rose type surface to convert to a lotus type surface. This may con eniently be used to manipulate a droplet by adhering the drop let to the surface of the mesh in its rose type state and then converting it (by application of a magnetic field, or of lateral stress, either tensile or compressive) into a lotus type state, thereby reducing adhesion and allowing release of the droplet.
[00046] A further aspect of the rose petal effect is, therefore, the abili ty to effecti vely transfer water droplet from the surface. When a 5 microti tre droplet is transferred from the fibrous mesh of the present invention to a second surface, the residual water from the droplet that remains on the fibrous mesh ma he less than about 10%, or less than about 5, 2, 1 , 0.5, 0.2 or 0. 1 % of the volume or mass of the original droplet . There may be essentially no residual water from the droplet that remains on the fibrous mesh following the transfer.
[00047] The inventors have surprisingl found that fibrous meshes which exhibit the rose petal effect commonly have an. RMS (root mean square) roughness of about 2 t about 10 microns. The EMS roughness may be about 2 to 5, 5 to 10 or 3 to 8 microns, e.g. about 2, 3, 4, 5, 6, 7, 8, 9 o 10 microns. Accordingly, a suitable method for monitoring the achievement of the desired rose petal properties (droplet attachment coupled with effectively quantitative droplet transfer) may be by monitorbg the RMS roughness. Thus electrospirming may simply be performed until the desired MS roughness is- achieved, at which point it may he inferred that the desired rose petal properties are also achieved. These may be achieve once there is about 0.2 to about 2mg of mesh per cm2, or about 0.2 to 1 , 0.2 to 0.5, 0.5 to 2. I to 2 or 0.8 to 1 Smg/cm1, e.g. about 0.2, 0.3, 0.4, 0.5, 0.6, 07, 0,8, 0.9, 1, 1.1, 1,2, 1 ,3, 1,4, 1 ,5, 1.6, 1.7, 1.8, 1. or 2mg/cm2. The mesh may have a thickness of less than about 50 microns, or less than about 45, 50, 35 or 30 microns, or of -about 20 to about 50 microns, or about 20 to 40, 20 to 30, 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
[00048 The mesh is commonly a polymeric mesh, i.e. the fibres comprise a polymer. In. some instances the fibres consist essentially of a polymer. The im'entors have surprisingl found that there is no requirement for the material, e.g. polymer, from which the mesh is made to be superhydrophobie or even highl hydrophobic. Indeed, it is possible to make fibrous meshes according to the invention from polymers such as polyeaprolactone which are not especially hydrophobic and in some instances from hydrophilic polymers. However hydrophobic polymers such as polystyrene may be used. It is therefore convenient to make the meshes from readily available and inexpensive materials. In some embodiments, therefore, the polymer is not a fluoropo!ymer. in other embodiments it is not a. condensation polymer. In particular, the polymer may not be
[00049] The polymer ma have a molecular weight (number average or weight average) of about 10 to about lOOOk a, or about 20 to 1000, 50 to 1000, 100 to 1000, 200 to 1000, 500 to 1000, 10 to 500, 10 to 100, 10 to 50, 50 to 500, 50 to 200, 50 to 100 or 1 0 to 200kDa, e.g. about 10, 0, .30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900 or ί OOOkDa.
[00050] In some instances the fibres comprise (or consist essentially of) a polymer composite, i.e. a polymer containing a filler. The filler may comprise nanoparticles, whereby the
nanopartleies do not have a substantial impact on the fibre diameter. The nanoparticles may be less than about 5Qnm in diameter, or less than about 40, 30, 20, 10 or Snm., or may be about 5 to about 50ora in diameter, or about 5 to 20, 4 to 10, 10 to 50, 20 to 50 or 10 to 20nra, e.g. about 5, 10, 15, 20,.25, 30, 35, 40, 45 or 50nm in diameter. They may be inorganic They may be for example iron oxide (e.g. Fe¾G iian-opartides), silica, titania, zirconia, alumina, zinc oxide etc. They may be magnetic nanoparticles. The abovementioned subst nces are readily available in nanoparticulate form, relatively inexpensive and readily functionalizable. They may be modified, e.g. using fiuoiOsilanes, so as to improve siper rydropliobicity, or may be allowed to increase hi concentration until they confer a more hydrophilic (thus rose-petal) effect on the resulting films. In some instances the presence of such nanoparticles may affect the physical properties of the. fibres, and therefore affect the physical properties (e.g. superhydrophobicity) of the fibrous mesh.
[000513 The inventors have observed that, when other factors are kept constant, an increase in the concentration of polymer in, the eiectrospinning solution results in a progressive change in the morphol ogy of the fibres of the fibrous mesh , Thus when the solution is quite dilu te (e. g. below about 8-10%w/v), the fibres have a large number of microbeads or swellings along their length. These microbeads ma be around 1-10 microns in diameter and ma be approximately spherical, or may be elongated along the length of the fibre, or may be oblate spherical, or may be ovoid, or may be approximately biconvex discoid shape, or may be toroidal, or may be irregular shaped, or may be some other shape. As the polymer concentration increases, the frequency .of these microbeads along the fibre length decreases, and when a concentration of about 20%w/v is reached there are very few or no microbeads. Thus the mean distance between microbeads along tlie fibre may b conveniently tailored by adjusting tli polymer concentration in the electrospmmng solution to anywhere from about 5 microns -upwards, it may be at least about 10, 20, 50, 100 or 200 microns. The mean distance between microbeads may be between about 5 and 500 microns, or between. 5 and 200, 5 and 100, 5 and 50, 50 and 500, 100 and 500, 200 and 500, 100 and 200 or 50 and 200 microns, e.g. about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 or 500 microns. The mesh may have a surface density of the microbeads of between about and about 500 microbeads per mm2, or about 3 to 600, 1 to 200, 1 to 100, I to 50, I to 20, 1 to 10, 10 to 500, 50 to 500, 100 to 500, 200 to 500, 50 to 200, 50 to 100 or 100 to 200 microbeads per mm2, e g. about L 2, 3, 4, 5, 10, .1.5,
20, 25, 30. 35, 40, 45, 0, 60, 70, 80, 90, 100, 150, 200, 50, 300, 350, 400, 450, 500, 550 or 600 icrobeads per mm2. There may in some instances be no microbeads. It is hypothesised that these microbeads may serve to space the fibres apart, thereby control ling the .'RMS roughness of the surface of the fibrous niesh and hence affecting the rose petal effect of that surface. These microbeads may be integral wit the fibres. They may comprise (or consist of) the same material as the fibres,
[00052] An alternative wa to affect the spacing of the fibres is to add discrete niicropartieles. As these are added separately, they may be a different substance to the fibres. They may for example be polymeric, or inorganic, e.g. metal oxide, or some other substance. They may be applied by means of a layer b layer construction of the mesh, whereby alternate layers of fibres and microparticles are laved down. .Alternatively they may be included in the electrospinning liquid. In this case they should be made of a substance that does not dissol ve in a solvent used in th electrospinning solution. The microparticl es may be spherical (i.e. may be microspheres) or may be polyhedral, irregular or some other shape.
[00053] it may assist in the production of 'the fibrous mesh if a surfactant is present in the electrospinning liquid. This surfactant may at least in part become incorporated into the
resulting mesh. The surfactant may be an ionic surfactant or may be a non-ionic surfactant. It ma be cationic or anionic. It may be amphoteric, it may be a quaternary ammonium surfactant. It may be an aliphatic (i.e. non-aromatic) quaternary ammonium salt. It may be an
alkyitrimethylammonium salt. The alkyl. group may be CIO to CI 6, or ma be a mixture of various chain lengths, predominantly in the range of 10- 16 (e.g. predominantly or exclusivel CIO, CI 1, CI 2, C13, CI4, CIS or 16). A suitable surfactant is a dodecyltriraethylammonium salt (e.g. chloride or bromide).
[00054] The fibrous mesh of the invention may be convenientl made by electrospinning.
Electrospinning in v olves extrusion of a polymer-containing liquid (i.e. art "electrospinning liquid") front a nozzle under an electric potential. The electrical potential may be between the nozzle and a substrate on which the substrate is formed. The liquid may be a melt of the polymer or may be a solution of the polymer. In the present instance it is more common to use a solution of the polymer. The concentration of polymer in the solution is commonly from about 5 to about 25 w/v. It may be about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 20 to 25, 10 to 20, 10 to Ϊ 5 or 15 to 20%, e.g. about 5, 10, 15, 20 or 25%. The concentration of polymer in the solution can
he used to control the orpology of fibres of the resulting fibrous mesh. This ca in turn control the time required to achiev the desired properties of the mesh.
[00055] As discussed above, it may be advantageous to incorporate a surfactant into the electrospinnmg liqiiid. This is commonly present in a concentration of about 1 to about lOmgaiil, or about 1 to 5, 1 to 2, 2 to 10, 5 to 10, 2 to 6 or 2 to 4mg/ml, e.g. about 1, 2, 3, 4, 5, 6, 7, Ss 9 or lOmg/ml. The requirement for a surfactant may depend on the nature of the polymer to be electrosptin. It has been found that when the polymer is polystyrene, the presence of
surfactant is desirable however with othe polymers, particularly amphiphiUc polymers, it may be less important to have a separate surfactant present.
[00056] The sol vent in. the electrosptnntng liqui d may be any solvent capable of dissol ving the polymer. The skilled person will readily understand that the range of solvents suitable for this will vary with the nature of the polymer. Suitable solvents in the case of eleetrospimiing of polystyrene include tetrahydrofuran, tetrahydropyran, benzene, toluene, xylene,
dichloromethane, chloroform, carbon tetrachloride, acetone, pyridine, dioxane, butanone, diisopropyl ketone, ethyl acetate, cyclohexane, carbon disulfide or mixtures of any two or more of these. For other polymers, other solvents ma be suitable although some of the above solvents may be usable for a variety of different polymers. The solvent is preferably a volatile solvent. It may have a boiling point below about 120°C, or less than about 100 or 80CC.
[00057] The eleetrospmning ma be conducted under a potential of about 5 to about 25 V , or about 5 to 20, 5 to 15, 5 to 10, 10 to 25, 15 to 25, 10 to 20, 10 to 15 or 15 to 20V, e.g. about 5, 10, Ϊ 5, 20 or 25 V. it may be conducted at a potential to working distance ratio of about 0.5 to about 5 Went, or about 0.5 to 2, 0.5 to L 1 to 5, 2 to 5, 1 to 2 or 1 to
1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5V/cm.
[00058] The nozzle from which the eleetiospiiining liquid is extruded may be about 0.5 to about mm in internal diameter, or from about 0.5 to 0.8, 0.7 to 1 or 0.6 to O.Smni, e.g. about 0.5, 0.6, 0.7, 0.8, 0,9 or I mm or may be more than 1 or less than 0.5mm in internal diameter, ft may be for example a 1 7G, 18G, 19G, 20G or 21G needle.
[00059] The atmosphere through which the eleetiospiiining is conducted may be maintained at a. temperature of about 5 to about 25°C, or about 5 to 20, 5 to 15, 10 to 25, 15 to 25, 10 to 20 or 15 to 20°C, e,g. at about 5, 6, 7, 8, 9, 10, 1 1 , 1.2, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24 or
25°€. it may be oiaintained at a relati ve humidity of about 30 to 70%, or about 30 to 60, 30 to 50, 40 to 70, 50 to 70 or 40 to 60%, e.g. about 30, 40, 50, 60 or 70%. The atmosphere may be air or it may be some other gas, e.g. nitrogen, argon, carbon dioxide etc. or may be a mixture of such gases.
[00060] The distance between the nozzle outlet and the substrate, i.e. the working distance, ma be between about 5 to about 20cm, or about 5 to 1.5, 5 to 10, 1.0 to 20 or 10 to 15cm, e.g. about 5, i 0, 15 or 20cm, or may be some other distance. The flow rate of electrospinnittg solution may be about 0.5 to about 2ml/'h, or about 0.5 to I, 1 to 2 or 0.7 to 1 3ml/h, e.g. about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 , 1.2, 1.3, 1.4, 1.5, 1 .6, 1.7, 1.8, 1.9 or 2ml/h. The flow rate may be about 25 to about SOOmg polymer per hour, or about 50 to 500, 100 to 500, 200 to 500, 25 to 200, 25 to 100, 25 to 50, 50 to 200, 50 to 100 or 100 to 200mg polymer per hour, e.g. about 25, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450 or 500mg polymer per hour. It may be about 0.05 to about 2 rag polymer per hour pe square cm of substrate, or about 0.1. to 2, 0.5 to 2. 3 to 2, 0.05 to 1 , 0.05 to 0.5, 0.05 to 0.1 , 0.1 to: 1 , 0.1 t 0.5 or 0.5 t 3 rag per hour per square cm of substrate, e.g. .about 0.05, - 1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, i, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2 mg per hour per square cm of substrate.
[00061] The surface characteristics of the fibrous mesh produced by the above method may vary with the time of extrusion. Therefore in order to obtain the desired properties, it may b necessary to continue the electrospinnmg for a specified time but no longer. It has been observed that as electrospmrmig progresses, the fibrous mesh is initially not superliydrophobic (i.e. does not have a static water contact angle of 350° or more). After sufficient time, the desired rose petal characteristics (superhydiOphobicity, adhesiveness to droplets and clean transfer of droplets) are achieved, if electrospinning is continued, the surface adopts the lotus leaf characteristics whereby it. is snperhydrophobtc but does not adhere adequately to droplets. The time required i order to achieve rose petal characteristics but not progress to lotus characteristics may vary depending on the electiOspinning parameters, the nature of the
polymer, the presence and nature of surfactant etc,
[00062] The time of extrusion is commonly about .15 to about 60 minutes, or about 1 to 30, 30 to 60 or 20 t 40 minutes, e.g. about 1.5, 20, 25, 30, 35, 40, 45, 50, 55 or 60 minuter It may be no more than about 70 minutes. This time ma depend on multiple factors, including the area over which the mesh is formed, the concentration of polymer in the extruded solution etc. The
time pf extrusion may be sufficient to achieve the rose petal type surface, and ma be insufficient to achieve a lotus leaf type surface, it may be sufficient to achieve a
simerhydrophobie surface and insufficient to achieve a lotus leaf type surface, it may be sufficient to achieve an RMS surface roughness (as measured for example by AFM or by white light interferometry) of about 2 to about i 0 microns, ft may be sufficient to achieve extrusion of about 0.01 to about 2mg of mesh per cm2. It may be for about 0.05 to about 0.2 minute per cm2 of substrate., or about 0.05 to 0.1 , 0.1 to 0.2, 0.07 to 0.13 or 0.1 to 0.13 minute per cm2 of substrate, e.g. about 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, Q.12, 0.13, 0.14, .15, 0.16, 0.17, 0.18, 0.19 or 0.2 minute per cm2 of substrate. It may be sufficient to form a film thickness of about 20 to about 50 mi crons, or about 20 to 40, 20 to 30 30 to 50, 40 to 50 or 30 to 40 microns, e.g. about 20, 25, 30, 35, 40, 45 or 50 microns.
[00063] The inventors have thus found a process to achieve a highly adhesive rose petal effect by means of a tunable hierarchical morphology. In a particular embodiment, mats or meshes of polystyrene nanoiibers/beads were synthesized by eleCttOspinning/s iaying into self-assembled hierarchical films for application as sticky super-hydrophobic coatings. Morphological modification leading to the rose petal effect was achieved, in a specific example, using dodecyl trimethyl ammonium bromide (a cationic surfactant). Coatings were developed through the elimination of beaded films (known for low-adhesion lotus leaf supet-hydinophobicit ), transiting wettin characteristics fro low-adhesion lotus-leaf 'super-hydrophobicity to highly adhesive rose-petal super*hydrophobieity. it is hypothesised that the microbeads along the fibres represent a transition zone between electrospinning and electrospraying. Thu it is thought that more dilute solutions of polymer have poorer cohesion and hence are more likely to form droplets, leading to beads rather than cohesive strands.
[00064] The inventors have observed that electrospinniti a moderately dilute polymer solution, in particular when a suitable surfactant is present in the solution, produces a fibrous mesh in which swellings, or microbeads, are present along the fibres. They have further observed that an increase in the polymer concentration in the liquid polymer compositio from which the mesh is eSectrospun gives rise to a decrease in the frequency of microbeads along the fibres. These microbeads appear to have aft effect on the physics of the surface of the mesh. It is hypothesised that a certain range of surfac roughness is required in order to achieve the desired "rose petal" effect. This roughness appears to be from about 2 to about 10 microns RMS. The surface
roughness may for example be measured using .white light interterometry or using atomic force microscopy.
[00065] The inventors have hypothesised that the microbeads along the fibre length serve to space the fibres away from each othe in order to achieve the desired surface roughness, lit the absence of the microbeads, it is necessar to continue the electrospinmng for a longer time, so as to achieve a greater tliickness, so that the fibres themselves serve to space fibres from each other and achieve the desired roughness. However if eiectrospinning is continued for too long, it is thought that the fibres, and microbeads, fill in the troughs so as to reduce the surface roughness arid therefore destroy the rose petal effect. Therefore it is important to achieve the correct balance between polymer concentration and time, and possibly also other parameters such as voltage, working distance, flow rate, humidity etc. so as to achieve the desired effect.
[00066] It is possible to achieve a similar surface roughness through other methods. One possible method involves the use of microparticles to separate the fibres. This may for example be achieved by layer by layer (LBL) synthesis.. Alternatively, a desired surface rou hness may be obtained by templating, microlithography and other methods. Most of these methods suffer from the disadvantage that they are slow, multistep, expensive and/or difficult to scale up. The present invention, however, provides a simple scalable process for achieving a surface exhibiting the rose petal effect.
[00067] Key structural, properties are determined to tune wetting properties from lotus leaf- to rose petal-like. Ultra-dexterous droplet manipulation is demonstrated by mechanically induced lossless transfer of micro-droplets between two super-hydrophobic coatings. As-developed coating were assessed for static water contact angle, contact angle hysteresis sliding angle, adhesion strength and complete droplet transference. Described herein is, therefore, a low temperature, reaction- free method for the facile and scalable synthesis of one-step sticky super- hydrophobic coatings. The best films produced herein exhibited static water contact angles of 152.3±i .8°, with a contact angle hysteresis of 50,3±0.81° with effective adhesion strength
(! Umg / 1 12.8μΝ / 143.6pNmm~2) and residual-free droplet transference properties.
[00068] The rose-petal effect i believed to occur within the transitional region between the Cassie-Baxter (non-wetting) and the Wenzel (full-wetting) system. This transition zone was
only recently classified as the Cassie- Impregnating wetting mechanism. In a typical Cassie- Baxter wetting regime, the contact angle (CA) is given 'by, $8 ~" Ef^msB^ 1 - [ 1 ]
On the other end of the spectrum, the contact angle on a rough surface exhibiting the Wenzel wetting regime is expressed as, ms0 ~ MfW$ [2]
However, in a Cassie impregnated regime, the CA is expressed as,
= ! - J ¾as£¾ ~ Xj [3] where Br is the roughness factor, ¾.. is the fraction of solid-liquid interface,, θ is the
characteristic static contact angle.
[00069] In an ideally smooth and homogenous surface, the static CA eonresponds to a unique equilibrium positio of the solid- liquid-air contact line (triple line). Cm a rough surface, equilibriums exist over a range of CA, The receding C A, 8 . generally represents the minimum CA, while the advancing CA, 8Sd , will represent the maximum CA, The difference between these measurements is termed as the contact angle hysteresis (CAH),
%s [4]
[00070] In contrast to both the Cassie and Wenzel system, the Cassie Impregnating mechanism, does not require air pockets between the highest asperities of the surface (Cassie), or full liquid penetration between micro-stoicturai features (Wenzel). Instead, this regime involves an intermediate state of wetting, where water droplets penetrate one or more levels of the micro- scale features:. Through these multi-level, penetrations, suc surfaces experience high CAH and high droplet adhesion. As such, the morphological surface structure of surfaces (pitch and density of micro-nano-structiires) is known to be vital in developing surfaces with varied wettin performance (super-hydiOphohicity with high or low adhesion).
[00071] The synthesis of low adhesion super-hydrophobtc surfaces (lotas effect) through the use of polystyrene and electrospinntng has been very well investigated. A variety of surfaces have been produced, demonstrating high contact angles with low sliding angles (SA). Most research findings suppor the understanding that super-hydiOpliobieit is derived from the most beaded surfaces. This is accounted to the formation of a highly di storted triple line with small pitch distances., facilitating the trappi ng of air . Interestingly., it has also been generally reed upon, that the use of fibers (micro) from electrospinning, would result in non-super-hydrophobic performance (static CA < 150°). However, the use of all intermediate model (beaded fiber morphologies developed using surfactants) for the development -of highly adhesive super- hydrophobic rose-petal surfaces has been scarcely investigated.
[00072] The investors have now demonstrated a scalable and facile elecirospinning technique in the preparation of a fibrous surface exhibiting the elusive "rose petal effect". In the examples pres en ted here in , ins tead of utilizing a combination of materials with hydrophiJic and hydrophobic components, polystyrene- was used in conjunction with a cationic surfactant (dodecyl trimeihyl ammonium bromide - DTAB). The surfactants incorporated were known to possess dual-properties in this system: 1) modification of spinning morphology and 2) increasing the adhesi v e properties of as-spun fibers / beads without severely influencing the fundamental chemical groups and properties of the material. The use of surfactants in the field of electrospmning has been conventionally used, to promote smoother, headless morphological development of nano fibers.
[00073] Effecti ve electrospitinmg of polystyrene (PS) micro- and nano-structures was initially achieved by systematic investigation of a broad set of process parameters including spinning distance, electric- potential, precursor concentration, composition and feed-rate (Table I). The incorporation of dodecyl trimethyl ammonium bromide (DTAB) was found to considerably increase contro of structural features, and homogeneity when used with this polymer. The coating morphology was then tuned to three distincti ve well-reproducible layered structures (Figure !a-fT, herein, further referred to as heavily beaded, partially beaded and fibrous. It should be noted that "partially beaded" may be further subdivided into "moderately beaded" and "niinoriy beaded" and these terms are used elsewhere herein. It will be understood that the density of beading is greate in moderately beaded films than, in mmorly beaded films. Thus the following guidelines may apply:
« Fibrous: coimnonly no visible siffface beads, bu in any event less than about 3 surface beads ;
• Partially beaded: about 3 to about 600 surface beads/ram':
« Minorly beaded: about 3 to about 150 surface beads/in m2;
• Moderately beaded: about ISO to about 600 surface beads/mm";
• Heavily beaded: over about 600 surface beads raro2.
[00074] Fibrous films (PTD20, Figure ic) consisted of a vertically stacked network of mesoporous fiber layers. They featured the smallest (< 100 nm) surface pore size distribution (Figure I f) and the largest variation in fiber diameters (Figure l c) with an average of 5.0 ± 0.7 μΐη. The heavily beaded films (PTDS3, Figure la) were made of a dense assembly (ca. 650 beads / mm2) of relatively small micro-beads of 7.1 * 0.2 μιη in diameter occasionally separated by very thin iianofibers of 176 ± 3 alii in diameter. While these small fibers displayed mostly pore free surfaces, the micro-beads revealed a mesoporous structure with most pores below 200 nm (Figure Id). PTD5 was composed primari ly of beads, with diameters of 8.6 ± 0.5 μητ, resembling hemispheres.
Table I . Polystyrene spun with and without DTAB at lOem w orking distance for time-tTia! analysis
Sample Effective Voltage Rel, weight % Morphologies
(kV/cm)
With ΠΤ.Λ B
PTD5 1.0 5 Beaded films <¾ I m o 25 10 Moderately beaded films
PT 15 S \> Muwriy beaded mm*
ΡΊ 1)2(1 2,5 Fibrous films o
\ lhmH I)• ΛΒ
PS5 i n 5 Beaded films >
PS15 J it> Heavily beaded hints„
PS2H 2.5 : Minorly beaded films &
[00075] A third distinctive morphology having a unique cross-sectional structure was achieved by controlled beading during electrospinning of fibrous films (PTDI , Figure l b). These were mostly composed of non-porous sub-micrometer'. fibers of 41.8 ± 38 urn (Figure lb/e) and few large beads (ca. 160 beads / mm") having an average diameter of .13.5 ± 0.6 pm. The latter had a similar surface pore, structure as that observed on the heavily beaded coatings with slightly large pore diameters distributed between 200 and 400 run (Figure le). PTDI 5 appears distinctively similar to PTDIO, consisting of beads and fibers, but with diameters of 1 1.8 ± 0.5 pm and 739 ±31 nm respectively (data not shown). A key feature of these partially beaded films was the self- assembly of a stacked structure of nano/micro-iibrous layers vertically spaced by the large micro-beads. This three-dimensional fiber layer distribution resulted in a nano-mesh structure with inter-Fiber pores ranging from a few to tens of micrometers. The sizes of the inter- fiber pores may be easily determined using rough measurement on SE data. It should be noted that this is only an approximate measurement due to oddly shaped pores formed by intercrossing fibers. The average sizes were around 5μοι with a standard deviation of .about '2 pm. However, fiber to .fiber distance, which is equated to pore size, could range up to about lOpm.
[00076] Simila : morphologies were observed in the films made without DTAB. PS 5 was composed primarily of beads, albeit at larger diameters than PTD5; PS20 was of a simila morphological construct as PTDI 0 and PTDI 5; PSl 5 was highl comparable with PTD8; while PTD20 remains to be uniquely fibrous and not duplicated In the films made without DTAB.
[00077] Thus the pores within the microbe-ads and or the fibres of the meshes of the present invention may be from about 20 to about 200nm, or about 20 to 100, 20 to 50, 50 to 200, 100 to 200 or 50 to lOOnm, e.g. about 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180 or 200nm. These may be measured for example by nitrogen adsorption or BET (specific surface area analysis by nitrogen adsorption). The rnicrobeads themselves may be from about 1 to about 2 microns in diameter, or about 1 to 10, 1 to 5, I to 2, 2 to 20, 5 to 20, 30 to 20 or 5 to lOmicrons, e.g. about 1 , 2, 3, 4, 5, 6, , 8, 9, 10, 1 1, 12, 13, 1 , 15, 36, 17, 18, 19 or 20 microns. The fibres may be about 0.1 to about 1.0 microns in diameter, or about 0.5 to. 10, 1 to 1 , 5 to 10, 0.1 to S.¬ O.I to 2, 0.1 to 1, 0.5 to 5 or 1 to 5 microns, e.g. about OJ , 0.2, 0.3, 0.4, 0.5, 3 , 1.5, 23, 2.5, 3, 3.5, 4, 4.5- 5, 6, 7, 8, 9 or 10 microns. The interfibre pores may be from about 3 to about 10 microns, or about 1 to 5, i to 2, 2 to 10, 5 to 1 or 3 to 8 microns, e.g. about 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 30 microns. These pore sizes and diameters may be determined by electron microscopy, e.g. SEM or TEM.
[00078] For all morphologies, Fourier 'transform infrared, spec troscopy (FT 1R) analysis of the electrospun films (Figure I ) reveal only the presence of polystyrene. This further indicates that DTAB is mainly contributing to the optimization of the film morphology with no alteration of i ts surface chemistry. This enables a structural, comparison of the wetting performance o f fibrous, partially and beaded, films. Furthermore, notwithstanding the large variation in micro- structural morphology, all films possessed the hierarchical esoporous conformation (Figure I d-f) typically required for super-hydrophobic materials.
[00079] Optical IJV-vis analysis of these three characteristic morphologies was performed as a function of the electrospin ing time to assess the impact of nano 'micro-stroctural teatures on the resulting bulk properties, and their evolution with increasing cross-sectional thickness. The fibrous films were the most transparent (Figure 1 h, circles), with transmittance in the visible range (λ - 600 nm) decreasing from 94% to 77% with deposition time increasing from 10 to 60 mm. This is in line with the low scattering propert es of micro-scale fibers and the inherently low absorption of polystyrene at these low photon energy levels. Most importantly, the transmittance decreased linearly with increasing deposition time indicating uniform, fiber formation and consistent structural properties within the whole range investigated. Up to 40 minutes, the optical properties of the partially beaded films (Figure Ih, triangles) closel followed that of the fibrous morphology with ca. 7% less transmittance. This is mainly attributed to the light scattering from the few micro-sized beads distributed in the nano-mesh structure ( Figure lb). Further increasing the deposition time considerably increased the optical losses through these films, resulting in more than 15% less transmittance than fibrous films at 50 and 60 min (Figure Ik, 'triangles and circles). This suggests that above 40 minutes deposition time, the beads reach sufficient surface density to scatter a. significant fraction of the incoming light. In line with the SEM analysis (Figure l a), the heavily beaded film were the least transparent (Figure Ih, squares) with up to 15-50% lower transmittance than purely fibrous films. This is attributed to the high density of light-scattering beaded roicrostructures. effectively coating the substrate surface . Within minor variations, the structural properties of this morphology did not undergo substantial distinctions with increasing deposition time.
[00080] The meshes of the invention may therefore have a transmittance at 600nm of at least about 70%, or at least about 75%, or of about 70 to 90%, 70 to 85%, 75 to 90% or 75 to 85%, e.g. about 70, 75, 80, 85 or 90%.
[00081] Polystyrene nauostructures prepanea^- ifh or without DTAB were farther investigated with respect to th resulting morphology (Figure 2). The use of DTAB is aptly noted for its morphological modifications over the entire range of electrospimiing parameters, creating a dominant fiber-forming zone at 1.5-20wt% polystyrene, between l-2.5kV/cm (Figure 2b), and a predominantly bead-forming zone at 5-10wt% polystyrene between 0,5-2.QfeY/c (Fig. 2b). On the other hand, the electrospiiining of polystyrene without DTAB (Fig. 2a) gave rise to only 2 separate domains, consisting of dommantly beaded and beaded fibrous zones. No clear region of dominantly fibrous domains evolved up to the usage of a 20wt% polystyrene solution (Figure 2a). The different morphologies revealed a very distinctive wetting profile with robust rose petal-like, wetting achieved primarily with the mexlerateiy or minoriy beaded 3D nano-mesh structures in films created with, DTAB (Table 2). For all films, the static contact angle (Figure 3) increased continuously with increasing deposition time up to 30 rain, except for PTDS, PTD20 and PS20 (Figure 3a,h). in fact, PTDS ne ver achieved super-hydrophobicity (CA 150°) while its counterpart, PS 5 (made without DTAB), was able to rapidly achieve super-hydropbobic performance within 20 minutes of deposition (Figure 3b). This can be explained by the much smaller beading structure in PTDS as compared to PS 5, which may be less robust to water impact. Similar to PS5, PS 15 achieved super-hydrophobit-ity after 30 min deposition, while PS.20 never achieved this. Super-hydrophobic wetting was attained for both heavily and partially beaded morphologies in films made with DTAB upon a deposition time of 20 irtin. In contrast, fibrous morphologies (i.e. PTD2.0) consistentl required thicker films, resulting initially in hydrophilic coatings and achieving mostly hydrophobic wetting. Super-hydrophobie adhesive wetting was obtained only by 60 minutes deposition time in fibrous films made with DTAB. This is attributed to the large pore size of this fibrous morphology facilitating direct contact with the underlying hydrophilic glass substrate, and thus requiring thicker coatings. Upon 20 minute deposition, the heavily beaded films made with DTAB resulted in consistent lotus leaf-like rolling super-hydrophobie wetting. Thi is attributed to the high density of hydrophobic
polystyrene beads that cover the substrate surface (Figure l ) effectively impeding water penetration in the lower film layers.
[00082] In contrast, the partially headed layered fiber morphology made with DTAB resulted initially in hydrophobic coatings and achieved rose petal-like Cassie-impregnating wetting at 20 to 40 minutes deposition time. Further increasing the deposition time to 50 and 60 minutes resulted in lotus leaf-like non-adhesive super-hydrophobicity (triangles). This behavior matches well with the observed SEM structure and UV-vis time evolution dynamic showing high bead
densities above 40 minute deposition. Here, it is proposed that sufficient nano-mesh thickness is required to completely avoid wate contact with the underlying substrate while exceedingly high film, thicknesses result in high bead density( Jow pitch distances), effectively leading to wetting similar to that observed for the heavil beaded morphology .
[00083] Samples exhibiting lotus leaf super-hydrophobicity were separated from those exhibiting rose petal super-hydrophobieity via a direct analysis of the sliding angle (Table 2). ExpeetecUy, most of the beaded films exhibited lotus leaf super iydrophobicity , with s liding angles of between 10° - 72° . The stiper-hydrophobic lotus leaf surfaces de veloped without DTAB possessed a lower range of sliding angle (ranging f om 10°-3S°} while those developed with DT AB consisted of a higher range of sliding angl es (rangin g from 28°-72p"), revealing enhanced, adhesion regardless of morphologies (Table 2), Interestingly, as the time of deposition was further increased to 50-60 mimites, both types of rose petal, surface (PTDIO and PTD15) experienced a transition towards lotus leaf surfaces, with sliding angles (albeit high) of 50-60°. This effect may be accounted towards the verall film thickness and a compacted nature of the wounded fibers (over the drum). When eleetrospimiing produces distinctive fibers, these entities are wounded onto a spinning drum at a high speed. At longer deposition times, this is envisioned to aid in compactin the lower surfaces during the winding process, while increasin overall bead density, leading to the formatio of a surface with low adhesion. This trend can be observed in PTDIO (moderately beaded fibers), PTD15 (minorty beaded fibers) and PTD2Q (pure fibers) respectively. It therefore appears that rose-petal properties appear as an
imerrnediate between non-superhydrophobic materials and lotus-leaf type materials.
Table 2. Wetting categories - non-super-hydrophobie (tion-SH)5 rose petal (sticky) or lotus leaf (w sliding angles)
Sample Type 10 min 20 min 30 rain 40 nun 50 min 60 min
Willi UTAH
beaded fibers Rose Sticky SH Sticky SH 49.5±5.09 4$.6±3,56
(PTDIO) Effect
(ΡΤΒ2Θ) Stick
SH
\\ jih^U D i AB
Beaded (PS5) Non-SH Lotus Lotus Lotus Lotus Lotus
10.9±1 .19 12.3 ; 0.52 14.9*0.51 26.7± 1 .00 38.3*2.18
beaded fibers Rose
(PS20) Effect
[00084-3 The structural-wetting correlations observed for these different morphologies were further investigated (Figure 4) by white light inter feroraetr (WLI). Up to 30 minutes deposition time, both heavily and partially beaded morphologies of films made with DTAB (Figure 4a, b) exhibited similar root mean square (mis) roughness (2 μηί) and thickness (25 μηι), with the former disp laying a higher densit of micro-sized structures (Figure 4c,d). This is in line w ith the SEM analysis (Figure la), and is attributed to the higher bead density in this morphology, increasing the deposition time increased the rms roughness of the heavily beaded films from 2 to about 4 μηι while the detected WLI thickness was nearly constant. These steady structural
properties axe in good agreement with the observed wetting behaviors of the heavily beaded, films, resulting i« lotus-like sitper-hydtophobicity for all deposition times.
[00085] In contrast, investigation ... of the partially beaded films revealed a fundamentally different self-assembly dynamics. Tbeir mis roughness increased rapidly from about 2 to 16 μηι with deposition time increasing from 30 to 60 mm (Figure 4a, triangles). In parallel, the film thickness increased from ea. 25 to 55 μιη (Figure 4b, triangles). Cross-comparison with CA measurement indicated that film thickness and MS roughness below 50 and JO μπι, respecti vely, are favourable for achievement of a Cassie-impregnating wetting state. This is attributed to the droplet adhesion mechanism of the nano-mesh morphology. In fact, while the beads resulted in the formation of a distorted three-phase line promoting super-hydrophobicity, the nano-fibrous mesh was found to serve as a penetrable layer for micro-droplet adhesion. Increasing the deposition time to 50 rnin, the nano-mesh films experienced transition to lotuslike behavior wit sliding angles of 40 - 50°. This is attributed to the increase in surface roughness and bead density (Figure 4d) with increasing deposition time that results in a hardly penetrable small-pore layer. These resul ts demonstrate - the .first effective synthesis of highly adhesive super-hydrophobic rose-petal coatings by low-cost scalable electrospi iing of optimal 3D nano/micro-structures,
[00086] Various surfaces identified with possible rose-petal effects were further analyzed for droplet adhesion and transfer properties (Figure 5), and revealed some surfaces with poor transferability (defective rose-petal effects), which were unable to execute a clean, droplet transfer (Tabl e 2), This could ha ve occurred as a result of excessi ve substrate-coati n g-water interactions, causing unwanted seepage of water into the porous coating, eventually preventing depinning through capillary and adhesion forces.
[00087] The super-hydrophobic surfaces developed with DTAB presented distinctive regions of both rose petal and lotus leaf characteristics, The rose petal effect was dominantly achieved on surfaces which were a hybrid of beads and fibers - beaded fibers (PTDIO and ΡΊΤ3Ϊ 5). Whil the sporadic presence of beads promoted a distorted three-phase line arid facilitated the super- hydrophobicity, the fibers provided a sub-layer for the impingement of droplets.
[00088] The feasibility of droplet manipulati on and transfer by these different morphologies was assessed in terms of maximal adhesion strength and percentage of volume transferred (Figure 5).
Despite the increasing research effort on rose petal coatings, very few studies have demonstrated the transfer process or assessed post- transfer residue. A 5μΙ. droplet was first cro s- transferred between 2 super-hydrophobic rose petal interfaces (Figure 5a). Thereafter, a droplet transfer from a super-hydrophobic rose petal surface to a hydrophilie counter substrate (glass) was also performed (Figure 5b). In both instances, the transfer was clean and without residue. On a related note, defective rose petal surfaces were unsuccessful in completely transferring microdroplets (Figure 5c), while exhibiting super-hydrophobic contact angles (> 150°). These defective rose petal surfaces have never been reported in the past. It appears that their existence occur at the sub-transitional zones between highly hydrophobic films and rose-petal super- hydrophobicity. These zones are hi ghl y unstable, and the depirming of microdroplets becomes difficult, thus leaving a residual droplet.
[000893 Here, the optimal, iiano-mesh structure resulted in a perfect rose petal-like Cassie- impregnatirsg state demonstrating super-hydrophobic wetting, pinning of 12 mg droplets and 100% volume transfer with no residue on the original coating. Notably, variations of this ideal rose petal-like behavior were observed. T he photographs of Fig. 5 were taken using 5 microiitre droplets, however similar results are obtained using larger droplets as described above.
[00090] The adhesion strength of all morphologies decreased sharply for deposition times above 1.0 min. The heavily beaded films led to non-adhesive superTiydrophobicity, the fibrous to highly adhesive hydrophilic/hydrophobic wetting, and the partially beaded to moderately adhesive rose petal-like pinning. This initial high adhesion state is attributed to interaction with the glass sttbstrate and is in good agreement with the static contact angle analysis.
[00091] Although the highest adhesion strength was achieved with PTD20 at 60 minutes, these surfaces suffered from unreliability w th persistent residual volume transfer. Furthermore, the excessive pimiin could potentially lead to contamination. These defective regimes are attributed to the high instability of excessi ve surface porosity stemming from a predominantl fibrous interface, giving rise to disproportionate capillary/adhesion forces, and thus preventing depinning. On the other extreme, the lotus leaf-like heavily beaded coatings resulted in a lossless transfer between coatings without, however, manipulation or control feasibility due to the low adhesio forces.
[00092] The best. naruMrtesh coatings of those prepared possessed a maximal adhesion strengt ofca. Ϊ 13 ± 20 μΝ corresponding to a droplet mass of 12 nig. These were the moderately
[PTDIO] and minoriy f PTD 15] beaded films made with DTAB, which were extruded for between 30 and 40 minutes (see Table 2). These are representative of effecti ve rose petal surfaces. They enabled a lossless micro-droplet transfer from a rose-petal film to a hydrophilic glass slides, and an unprecedented cross-transfer of a 5 ul drople between two super- hydrophobic rose petal -like interfaces. This unique material, wetting performance is of great potential fo the development of ad vanced water and droplet manipulation devices.
[00093] The droplet transfer mechanism of the best performing nano-mesh structures (40 min deposition PTDI O and PTD15 as discussed above) were further investigated in detail. A main differenc was observed between transfer from rose petal to equi valent rose petal or uncoated glass substrates. Upon contact, the latter showed an immediate (< 33 ms) desorption of the micro-droplet, while the former first required a mechanically induced pressure between the two substrates, and thereafter their separation along the vertical axes. These droplet transfe dynamics were attributed to the different water desorption mechanism (Figure 6). Contact with the hydrophilic glass substrate resulted in the immediate horizontal spreading of the water on the lower hydrophilic interface. As a result, the droplet three-phase line on the top nano-mesh coating experienced a swift horizontal pull. This rapidl enl rged the contact area with the nano- mesh decreasing the amount of water tr apped in each p ore. As a result, verti cal pulling by gravity and surface tension was sufficient to overcome the residual La lace pressure to exit the pores, inducing a force-Jess outflowing (Figure 6a),
[00094] In contrast, contact with another super-hydiOphobic nano-mesh coating preserved the initial droplet shape (Figure 6a) and required applicatio of an external orthogonal force to release the droplet from the initial substrate. This slower mechanical ly- induced release enabled optical analysis and quanti fication o th Laplace pressure and surface tension acting on the nano-mesh ( Figure 6b). Adhesion of the droplet to another rose petal-like coating was achieved by its compression between two substrates (Figure 6b, inset). This resulted in the highest Laplace pressure (Figure 6b, circles) and minimal surface tension, forces (triangles). The Laplace pressure acting on the contact area (145 ± 0.08 μ mm") was sufficiently high to push the water-air interface through the pore of the bottom substrate nano-mesh. This enabled infiltration of the inter-layer spacing of die mesh resulting in the rapid relaxation of the curved water-air interface. In this state, the system experiences a local energy minimum, This is represented by
an identical bottom and top adhesion strength and results in a slight repulsi o force between the two substrates (Figure 6b, squares). Removal of the droplet from the surface requires
overcoming again the maximal pressur required to squeeze the air-liquid interface through the naiio-mesh pores, effectively resulting in droplet adhesion.
[00095] Increasing the substrate distance (Figure 6b) increased the surface tension force while decreased the repulsive Laplace pressure components resulting in a pulling force between the substrates. This ultimatel leads to a higher force applied to the to nano-roesh du to the weight of the droplet (Figure 6b, squares). As a result, partial elastic deformation of the top nano-mesh (Figure 6b, inset) occurs, followed b pore enlargement and eventual droplet release. A maximum pulling force of 133 ± 0.4 fi mf1 was computed on the top surface just before droplet release. This force was found to. be within 92% of the. adhesion, strength/measured by
gravimetric analysis.
[00096] The potential range of rose-petal surfaces were further assessed for maximum adhesion strength (Figure I l a) to a super-hydrophobic droplet which is pimied at approximately I .Qrnm at its feet. The average maximum mass achievable by the rose petal surfaces was approximately 1 IJrttg / 1 10.7μΗ. This local maximum occurred primarily for beaded fibers (FTDlO and
PTD15) between 30-40 minutes of deposition.
[00097] The complete/incomplete transfer of mierodroplets based on potential rose-petal surfaces were also analyzed and reported (Figure b). The present specification therefore presents the first analytical means to determine the true efficiency (through drop transference ) of surfaces claiming the rose-petal effect. As observed (Figure 1 lb), the beaded fiber surfaces (developed at 30-40 minutes) exhibited the most optimal transference properties, with 100% transference of the pinned microdroplets (5μ1),
[00098] I order to gain a better understanding behind the tunable wettabilit of polystyrene surfaces by configuring concentration and spinning parameters, key samples were chosen tor contact angle hysteresis assessment. Samples chosen were of 4 variants (under the PTD series which used .surfactant): 1) lotus super-hydrophobioity (FTD8), 2) rose super-hydrophobicity (2 samples - PTDIO and PTD 15), 3) non-super-hydrophobie (PTD2Q). Samples deposited for 40 minutes were assessed for differing adhesi ve properties, after detailed assessment of the stabilit of the as-synthesized rose petal surfaces (Table 2),
[00099] As observed in Figures 7 and 8 , the 3 types of morphological pro files led to di fferent wetting characteristics, with distinctively unique contact angle behaviors. Contact angle hysteresis was computed from the advancing contact angle at 5μ1 ±0.5 μΐ and the receding contact angle at 0.5μ1±0.1 μΐ. Data is presented in Table 3.
[000100] The contact angle hysteresis lor the lotus surface (PTD8) was found to be around 42°, qomparable- to previous studies classified for low adhesive surfaces. Here, we present, for the first time, electrospuii polystyrene-based rose-petal surfaces (PTD 0, 15), with slightly higher CAE! (50-60°), showcasing greater adhesion. The nan super Tiydropfiobie surface exhibited a contact angle hysteresis of 77.7°, representing a fairly distinctive difference from the super- hydrophobic sticky/slippery surfaces (Figure 9).
[000101 J This aaaiysis shows succinctly that surfaces with different wetting characteristics, may be generated from a single material, through careful tunin and modification of surface morphological design.
Table 3. Contact angle hysteresis, PTD8 (lotus, low adhesion)., PTD 1.0, 15 (rose, medium adhesion) and PTD20 (non-super-hydrophobic, high adhesion)
Sample PTD8 PTD1 PTD 15 PTD20
[000102] In contrast to this, the heavily beaded fiber surfaces and pure fibrous surfaces possessed rose petal qualities at higher deposition times (60 minute). Contrary to the transitional behavior of fibrous surfaces, the heavily beaded fibrous surfaces transited from the lotus leaf effect to the rose-petal effect. Ironically, this effect could also be analyzed via the film thickness, albeit in an alternate sense. As heavily beaded fibrous surfaces are .formed on a spinning drum, less winding of continuous fibers occurs. Instead, scatters of heavily beaded material are formed, and become electrostatically drawn onto the spinning drum. This forms a discontinuous surface (which gives the original super-hydrophohtctty). However, as time proceeds and excessive material is deposited, the top laye of the film becomes loose, due to the lack of binding material (conmiuous fibers), thus allow ng a potenti al water droplet to pin, enhancing capillary effects and increasing adhesive forces. This trend can be observed in PTD8
(heavily headed fibers) and PS 15 (heavily beaded fibers) respectively where adhesion was increased with increasing deposition time. Specifically, it was noted that the film thicknesses increased largely over time (Figure 7b.)- but with .minimal increment in RMS roughness.
[000103] The electrospi iing of polystyrene infused with DTAB has successfully developed tunable lotus leaf and rose petal interfaces exhibiting key wetting character stics. The transitional regimes between the domains demonstrate that tunable surfaces can be achieved with careful adj ustment of surface morphological structures.
[000104] These differing effects are thought to relate to the effective pitch distances generated by the electrospun material, which may come in the form of microbeads, beaded nano/micro fibers and microfibers. Small pitch distances from continuous layers of mierobeads provided effective sliding performance, while larger pitch distances transited towards greater adhesion and lowered contact angles (rose petal effect), eventually becoming no super-hydrophobic.
[000105] As demonstrated, these surfaces are able to serve as "mechanical hands" for the lossless transit of microdroplets, providing gr at potential for applications involving
microfluidics. Given the ease of possible modifications that nanofibrous surfaces could undergo, they may even hold the potential for actuated droplet control .
[000106] In conclusion, a novel nano/miero-stnrctural material enabling reversible highly adhesi v e super-hydrophobic pinning of micro-droplets has been demon strated. This enables the robust one-step synthesis of biomimetic rose petal coatings by a scalable low-cost method. A superior nano-niesh film morphology is obtained by three-dimensional inter-stacking of biocompatible inert polystyrene nano -fiber layers separated by micro-beads, leading to an ideal Cassie mpregnating wetting state. This enabled the first complete miero-droplet transfer between two adhesive super-hydrophobic surfaces, showcasing unique potential for water manipulation. This is a key step required for multi-step and multi-droplet parallel processing and thus represents a considerable leap-forward ia numerous technologies such micro tluidies systems, functional dry adhesives, actuated droplet control systems, actuated droplet control systems and micro-reactor arrays. These findings demonstrate a low-cost scalable process to engineer and rapidly fabricate tailored biomimetic rose petal-like nano/micro-strixctiires capable of providing highly precis manipulation, of small water volumes. This offers a new and
unexplored, material property with potential applications ranging from biosensing to water purification.
[000107] Some applications- whic are envisaged for the fibrous mesh of the present invention are set out below.
Microf!uidic Devices
[000108] The ability to control droplet motion without leaving residue on nucrofiuidic devices is important in many wetting applications. This is currentl achieved using various techniques, one of which involves electro-wetting through the use of CNT electrodes. Recently, the rose petal effect has also been used in m icro flui die devices through a technique of ink-jet printing on super-hydrophobic lotus surfaces in order to induce droplet pinning. The ability to control and move a droplet through mechanical, electrical or other means remains a challenge which would further improve and push the boundaries of .microfluidics. The present invention provides a direct and scalable alternative to conventional microfluidie devices with a. particular emphasis on droplet motion and control.
Array Micro -reactors , DN A sequencing and Miero-bioreactors for Dru Discovery
[000109] The use of micro-reactors, in line with other techniques, furthers tire efficiency of lab- on-chip or bio ssay technologies. Arrays of 'micro-reactors wil also provide high throughput combinatorial studies, with extensive implications i fields related to biology, chemistry and engineering.
[000 Π0] DMA sequencing also belongs to a sub-set of micro-reactor development, where sealed domains and channels of reaction zones are used i immobilizing and subsequently analysing DMA templates. The use of an unsealed, but sterile rose-petal like environment provides much greater versatility towards these analytical techniques.
[00011 i] Single ceil analysis and antibodies sorting have been demonstrated through the use of isolated droplet analysis. Current mierofiuidic technologies rely on the use of a carrier fluid (oil), which carries distinct droplets along a channel for analysis. Through the use of a carrier fluid-free technique, the rose-petal effect, may be used as a potential cheap and scalable substitute for these current technologies.
Bio-sensing
[0001 12] Applications related to bio-sensors and other instruments requiring clean
contamination-free transport and analysis of micro-droplets will benefit most from the industrial implementation of the rose-petal effect. Exploitation of the rose-petal mechanism enables improved nanowire based senso devices which are currently used in many lab-on-chip technologies which requires the use of micro-droplet arrays for chemical bio sensing.
Functional Dry Adhesives
[0001 13] The first rose- etal -like surfaces were actually attributed to the "gecko-feet" effect, a parallel biomimetic effect which emphasizes on dr adhesion. Although the t o effects are now independently pursued, this represents a potential for the achievement of both effects through the same mechanism. Rose-petal-like surfaces could in fact .serve as super effective dry adhesives.
Experimental Section
[000 14] Polystyrene (Sigma Aldrich, Mw = 280,000} (PS) solutions were made by dissolving respective masses (5-20 relative weight % of the solvent mass) in 10ml of teteahydroruran (Sigma Aldrich, anhydrous, > 99.9%) (THF). Dodeeyl tiimethyl ammonium bromide (Sigma Aldtich, > .98%) (DTAB) was also added to an alternate 'set. of polymer solutions at
concentrations of 3.0 g m.L. .Polymer solutions were stirred at 300 RPM for at least 24 hours prior to electrospinnmg. The solutions without DTAB were clear while those with DTAB appeared slightly clouded. Care was taken to ensure a homogenous suspension prior to loading into a syringe for electrospinning,
[0001 5] An applied voltage of 5-25 kV was used with a working distance and flow rate of 10 cm and 1.0 mL h"1 respectively, providing homogenous coverage of fibers beads on glass substrates mounted on a spinning drum for 10 minutes. The spinning drum had diameter I Ocm and length of 10cm, providing total area of 31.4cm*- Coating morphologies belonging to films were determined by optical microscopy. Various selected morphologies (beads/beaded fibers/fibers) were further spun for 1 hour over a surface of about 80cm2 (on -a spinning drum rotating at between 300-400 RPM). Bleetrospinning was conducted using an 18G needle at: 10- 2G°€ at a relative humidit of between 40-60%.
[0001 1 ] Coatings collected on glass slides were stored overnight to facilitate the completion, of solvent evaporation prior to further testing. The static water contact angle (CA) was measured by placing and averaging 5 drops (2mm dro height) of deiooized water (5-6 μΐ) on the sample surface. The sliding angle (SA) was determined b placing a 5 Τ drop of deionized water directly on sample surfaces prior to tilting via a goniometer. Results were averaged across 3 readings. The contact angle hysteresis (C AH) was measured based on the drop-out advancing contact angles (θ¾ι :, 0 to 5" ,uL, 3 readings) and evaporative receding angles (θ,¾), of which the latter utilizes natural evaporation of a drop of deionized water (5 μϊ_, 3 readings). The evaporative procedure for obtaining receding contact angles was chosen due to its greater sensitivity in contrast, to other means, such as the drop-in technique, a no interference from the deposition needle is present during wiihdmwal. The time of evaporation was approximately 70- 80 minutes at 20-25 ¾C and a relative humidit of 40-50 %. Readings were taken at 5-minute intervals for the first 50 minutes and thereafter at 1 -minute intervals until the droplet could no longer be determined via the computational fit (The fitting was deemed inaccurate below 0.5 p.L). Contact angle hysteresis (CAB) was computed from the advancing contact angle at 5p.L ± G.I μΐ using the standard drop- in drop-out (DIDO) techniqne (0.5 L/s) and the evaporative recedin contact angle at O.SpL ± 0.1 μL·, Residual droplet analysis from tire cross-transfer of water droplets was also assessed via optica! fitting (before and after transfer to a hydrophilic glass slide). Dynamic and static images were recorded using a KSV CA 2.00 contact angle goniomete (Finland) with a. heliopan BS43 camera (Japan). The CA, SA and CAB were computed by a commercially available (CAM2008) program.
[0001 17] Adhesion forces of sticky super-hydrophobic samples were analyzed via bot optical and mechanical methods. The optical method: involved the analysis of Laplace induced, surface tension and gravitational forces on the system,
F— rrHf f— -|-— |— 2 ssmM | - ?»ejf
where σ is surface tension (0,072 N/m), Θ represents the contact angle (measured on the right and {eft of droplet accounting to instances of asymmetry), f denotes the surface roughness, m^g is the gravitational force on the droplet and F is the net force centered on the top plate. Surface roughness (f) of 1 was used as per the standardized formulae. The actual f was computed based on 2 inverted droplets at equilibrium via equation 3 at 1.05 ± 0.01. An average contact area. (JTD ) of 0,90 ± 0.03 mm" was used up to the beginning of significant droplet detachment.
Thereafter* the contact area was measured for each frame v rying from an initial 1 ,30 mnr to
0.2 mm2. All frames were assessed using MSVisio at 400% magnification of native images. Adhesion forces of sticky super-hydrophohie samples were analyzed via a set-u which provided measurements of the maximum drop size (mass) hel d by inverted droplets (with a pinned feet of approximately I .Oram in diameter) via a mass balance with an accaracy of ±lmg. Detailed experimental steps are set out below, with reference to Fig. 12, Specific adhesion strength was calc ulated based on the pinned base area (1mm diameter) of the droplets on the best performing surfaces.
. Align stands using a spirit level to ensure horizontal alignment.
2, Set-up is placed onto a mass balance and zeroed.
3. A 5-6 μΐ drop is placed onto the surface using a 25G needle. This ensures a pinning diameter of the droplet of about 1mm. Excessive droplet size may encourage a larger pinning diameter/ vertical penetration, leading to false adhesion values.
4. S ubstr ate is then carefull inverted and placed, onto the stands,
5. Water is manuall added to this drop (sub-dropwise 1 -2mgJ) using a 25G needle. Direct water contact between the pendant drop and needle should be avoided.
6. Finally, as the mass overwhelms the surface and drops, it detaches and lands on the bottom catchment slide.
7. Captured footage of the mass balance combined with the final mass measured allows computation o f the net force exerted by the surface on the dro plets by virtue of mass.
8. Steps 2-8 are repeated for 3 times and an average is taken as the maximum adhesion force.
[000118] Morphological optimizations were first conducted using a light microscope (Nikon Eclipse E200®, TV lens 0.55x DS) on coated glass substrates. These optimization experiments were conducted twice to ensure repeatability (under controlled, environments). The 5 distinct morphological distinctions were noted based on observin the prevalence of beads on an area of about 0.31 mm" (480μηι x 640μήι), Table I. Selected samples were also later analyzed via scanning electron microscopy and white light inter ferometry.
[0001 1 ] Select samples were analyzed using a Zeiss UltraPl us® analytical scanning electron microscope (FESEM) at 3kV. Prior to examination., SEM specimens were platinum sputter- coated for 2 min at 20 rxuA. Average fiber and bead, dimensions were analyzed via Image i.
[000120] Selected sets of samples were also analyzed via a white light interferometer, at 5 magnification with a field o Ix via th vertical scanning interferonretry (VSl) mode. An area of approximately 1.24mm2 was analysed (typical wetting on of super-hydrophobie surfaces). A baekscan of 60Ltm and length of 50μη¾ was used with a modulation of 2% in order to cover the maximum height of films.
U V-vis analysis was conducted using a mieroplate reader (Teean 200 PRO®, Switzerland) from 300-800 nm wit 10 scans per cycle. Fourier transform infrared spectroscopy (FTIR-AT , Broker-Alpha, U.S-A) was performed (16 scans ftom 400 to 4000cm"1) on samples to verify possible chemical modifications.
Claims
L A fibrous mesh ha ving a static water contact angle of greater tha about I SO0, wherein:
♦ a water droplet of about I Otng adheres to a horizontal underside of said fibrous mesh without detaching therefrom; and
♦ transfer of said droplet from said underside to a second surface occurs suc that essentially none of the water of said droplet remains adhered to said fibrous mesh.
2. The fibrous mesh of claim 1 having an RMS surface roughness of between about 2 microns and about 1.0· microns.
3. The fibrous mesh of claim 1 or claim 2 having a contact angle hysteresis of about 45 to about 70".
4. The fibrous mesh of any one of claims I to 3 wherein fibres of said mesh com pri se a po ly me .
5. The fibrous mesh of claim 4 wherein said fibres comprise a polyme composite.
6. The fibrous mesh of claim 5 wherein the composite comprises nanoparticles embedded in the polymer.
7. The fibrous mesh of claim 6 wherein the nanoparticles ate inorganic
nanoparticles.
8. The fibrous mesh of claim 7 wherein the inorganic nanoparticles are iron oxide nanoparticles.
9. T e fibrous mesh of any one of claims 4 to 8 wher in said polymer is a hydrophobic polymer.
1.0. The fibrou mesh of claim 9 wherein said hydrophobic polymer is polystyrene.
11. The fibrous mesh of any one of claims 4 to 8 where n the polymer is
polycapro lactone .
12, The fibrous mesh of any one of claims 1 to 11 comprising fibres which include microbeads along their length, said microbeads being integral with the fibres.
1.3. The fibrous mesh of claim. 12 wherein the fibres have on average no more than 1 microbead per 100 microns length.
14. The fibrous mesh of claim 1.2 or clai 13 having a surface density of sai n krobeads of about 3 to about 600 microbeads per mm".
15. The fibrous mesh of any one of claims I to 1 ha vin a thickness of less than about 50 microns.
16. The fibrous mesh of any one of claims 1 to 1.5 comprising a plurality of microparticles, wherein fibres of the mesh are separated by said microparticles and said microparticles are not integral with the fibres.
17. The fibrous mesh of any one of claims 1 to 16 comprising a surfactant.
18. The fibrous mesh of claim 17 wherein the surfactant is a cationic surfactant
1 . A process for mak ng a fibrous mesh having a static water contact angle of greater than about 150°, wherein::
* a water droplet of at l east 1 Omg adheres to a horizontal, underside of said fibrous mesh without detaching therefrom; and
* transfer of said droplet from said underside to a second surface occurs such that essentiall y none of the water of said droplet remains adhered to said fibrous mesh: said process comprising electrosptnning a liquid polymer composition through a nozzle for sufficient time to form said fibrous mesh.
20. The process of claim 19 wherein the liquid polymer composition is a solution of a polymer.
21. The process of claim 20 wherein the polymer is present in the solution at a concentration of from about 5 to about 20%w/v.
22, The process of claim 20 or claim 21 wherein the sol ution com prises a surfactant.
23. The process of claim 22 wherein the surfactant is present in the liquid polymer composition at a concentration of from about 2 to about 4mg/ml.
24. The process of an one of claims 1 to 23 wherein the sufficient time is sufficient to a chie ve an RM S s urface roughness of between about 2 mi crons and abo ut 10 microns,
25. The process of any one of claims 19 to 24 wherem the sufficient time is sufficient for extrusion of about 0.2 to about 2mg of* mesh per cm*.
26. The process of any one of claims 1 to 25 wherein th suffici ent time is about 20 to about 60 minutes,
27. The process of any one of claims 1 to 26 wherem tli sufficient time is about 0.2 to about 1 minute per cm* of substrate.
28. The process of any one of claims 1 to 27 wherein the electrospinmng is conducted at a voltage of about 5 to about 25kV.
29. The process of an one of claims 19 to 28 w'herein the nozzle, has an internal diameter of about 0.5 to about Inini.
30. A process for transferring a liquid droplet from a fibrous mesh according to any one of claims i to 18 to a second surface, said process comprising:
# bringing said second surface in contact with said liquid dro ; and
• withdrawing die second surface from the fibrous mesh so as to detach said liquid drop from the fibrous mesh;
wherein substantially no liquid from the liquid drop remains on the fibrous mesh following said detaching.
31 . Us of a fibrous mesh according to any one of claims 1 to 18 m a microf!oidic device.
32. Use of a fibrous mesh according to any one of claims 1 to 18 in a biosensor.
33. Us of a fibrous mesh according to any one of claims 1 to 18 as a dry adhesive surface.
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Non-Patent Citations (3)
Title |
---|
D. EBERT ET AL.: "Wear-resistant rose petal-effect surfaces with superhydrophobicity and high droplet adhesion using hydrophobic and hydrophilic nanoparticles", JOURNAL OF COLLOID AND INTERFACE SCIENCE, vol. 384, no. issue 1, 4 July 2012 (2012-07-04), pages 182 - 188, XP055315681 * |
J. MEIHUA ET AL.: "Superhydrophobic Aligned Polystyrene Nanotube Films with High Adhesive Force", ADVANCED MATERIALS, vol. 77, 30 June 2005 (2005-06-30), pages 1977 - 1981, XP055315667 * |
X. DEZHI: "Fabrication of raspberry SiO2/polystyrene particles and superhydrophobic particulate film with high adhesive force", JOURNAL OF MATERIALS CHEMISTRY, vol. 22, 14 February 2012 (2012-02-14), pages 5784 - 5791, XP055315680 * |
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WO2017062497A1 (en) * | 2015-10-05 | 2017-04-13 | Bvw Holding Ag | Textiles having a microstructured surface and garments comprising the same |
TWI715643B (en) * | 2015-10-05 | 2021-01-11 | 瑞士商Bvw控股公司 | Textiles article |
AU2016333984B2 (en) * | 2015-10-05 | 2022-01-27 | Bvw Holding Ag | Textiles having a microstructured surface and garments comprising the same |
EP4098799A1 (en) * | 2015-10-05 | 2022-12-07 | BVW Holding AG | Textiles having a microstructured surface and garments comprising the same |
TWI787690B (en) * | 2015-10-05 | 2022-12-21 | 瑞士商Bvw控股公司 | Textiles article |
US11613461B2 (en) | 2015-10-05 | 2023-03-28 | Bvw Holding Ag | Textiles having a microstructured surface and garments comprising the same |
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