CN102366712B - Method for modifying microporous membrane wettability by utilizing low pressure-forced Cassie state effect - Google Patents
Method for modifying microporous membrane wettability by utilizing low pressure-forced Cassie state effect Download PDFInfo
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- CN102366712B CN102366712B CN 201110301876 CN201110301876A CN102366712B CN 102366712 B CN102366712 B CN 102366712B CN 201110301876 CN201110301876 CN 201110301876 CN 201110301876 A CN201110301876 A CN 201110301876A CN 102366712 B CN102366712 B CN 102366712B
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Abstract
The invention discloses a method for modifying microporous membrane wettability by utilizing a low pressure-forced Cassie state effect. The method comprises the step of: inducing a liquid drop on a microporous membrane with the aperture of 10-100 mu m to be changed from a Wenzel state to a Cassie state at the room temperature by utilizing relative pressure of 100-300 Pa, so as to modify interfacial wettability property of the microporous membrane. Before the implementation of the above-mentioned step, preferably, surface finish is performed on the microporous membrane by adopting a surface modification technology. Under a same micropore structure, the larger the contact angle of the liquid drop on the surface of the modified microporous membrane is, the smaller the critical pressure of the forced Cassie state of the microporous membrane is. The invention provides a novel approach for designing a superhydrophobic surface. Compared with the common superhydrophobic surface, the microporous membrane has the advantages of reducing the degree of dependence on a low surface energy substance and a surface micro-nano fine structure, and decreasing the probability of failure of the surface superhydrophobic function when external pressure and the surface fine structure are damaged, therefore wide application prospect is obtained.
Description
Technical field
The present invention relates to a kind of method that changes the microporous barrier wetability, relate in particular to a kind of method of utilizing low force Cassie state effect to change the microporous barrier wetability.
Background technology
Hydrophobicity or wellability are one of key characters of the surface of solids.In recent years, the research of super hydrophobic surface has caused people's concern more, and so-called super-hydrophobicity generally refers to that the contact angle of the surface of solids and water is greater than the superficial phenomenon of 150 °.The understanding of people to super hydrophobic surface, the main automatically cleaning phenomenon from various biological surfaces.Barthlott and Neinhuis, by the microstructure of observation of plant leaf surface, think that this self-cleaning feature is jointly to be caused by the mastoid process of micrometer structure on rough surface and the wax of surface existence.Thereafter the people such as Feng has carried out further analysis to the lotus leaf surface micrometer structure, find also to have nanostructured on the lotus leaf surface mastoid process, and the trapezium structure that this micrometer structure combines with nanostructured is the basic reason that causes that the surface of solids is super-hydrophobic.By the analysis to leaf surface of plant, Many researchers has been launched the development of super hydrophobic surface.
In general, can prepare by two kinds of methods by super hydrophobic surface: a kind of is to build coarse structure on the hydrophobic material surface; Another kind is to modify the material of low-surface-energy on rough surface.Its target is the formation that promotes air cushion between drop and material surface, realizes drop Cassie state, the decrease of simultaneous fluid resistance.But, from thermodynamics, analyze, Cassie state drop on the rough surface of most of materials is metastable state, the Wenzel state is stable state, once external pressure overcomes the energy barrier from Cassie to the Wenzel state-transition, gas-solid interface disappears, and becomes liquid-solid interface, thereby causes surface super hydrophobic effect inefficacy.In addition, the micron/nano fine structure of super hydrophobic surface also easily is subject to the factors disrupt such as extraneous friction and causes super-hydrophobic effect and lost efficacy.
Therefore, explore a kind of tackle external pressure be not subject to nano-micrometre fine structure destroying infection and keep the method for super-hydrophobic effect to there is important using value.
Summary of the invention
Technical purpose of the present invention is to provide a kind of method of utilizing low force Cassie state effect to change the microporous barrier wetability.
The present invention realizes the technical scheme that above-mentioned technical purpose adopts: this method is at room temperature, utilize the relative pressure of 100～300Pa, induce drop on the microporous barrier that aperture is 10～100 μ m to be changed to the Cassie state by the Wenzel state, change microporous barrier interface wetting characteristics.The aperture of microporous barrier is larger, and on microporous barrier, drop reaches and forces the critical pressure of Cassie state less.
Before carrying out above-mentioned steps, also can adopt process for modifying surface to include but not limited to that plasma modification technique carries out finishing to microporous barrier.By in the vacuum chamber of the ex vivo treatment instrument such as microporous barrier is fixed on, adopt CF4 as working gas, regulating the vacuum chamber operating pressure is 10～50Pa, power 20～100W, processing time 1～30min.Under the identical micro pores structure, after modification on the microporous barrier surface contact angle of drop larger, on microporous barrier, drop reaches and forces the critical pressure of Cassie state less.
The principle of the inventive method is: under general condition, on the surface of solids, droplet morphology is affected by the tension force between the gas-liquid-solid three phase boundary.When liquid-solid interfacial tension is greater than gas-solid interface tension force, solid is not soaked by liquid.Under room temperature condition, on non-super-hydrophobic microporous barrier, drop is in the Wenzel state.After to microporous barrier one side, providing impressed pressure, on microcellular structure, the liquid film pressure increases.According to the Young-Laplace equation, along with the increase of pressure, the drop subsequent corrosion reduces.After external pressure reaches a certain critical value, on microporous barrier, drop starts to be changed to the Cassie state by the Wenzel state.The microporous barrier aperture structure is also the key factor that affects its surperficial drop state-transition.When the microporous barrier micropore size is larger, on micropore, the liquid film radius of curvature is larger, and the additional pressure of liquid film is less, thereby realizes the also corresponding reduction of additional forced draught of drop state-transition.Therefore the drop state variation critical pressure of micron order texturing microporous barrier reduces along with the increase in aperture.
In addition, by process for modifying surface such as plasma modifications, microporous barrier is carried out to finishing, change the microporous barrier surface free energy, affect liquid-solid surface tension, and change without drop initial configuration on the microporous barrier surface of external pressure.After adopting the low-surface-energy material to the microporous barrier finishing, the microporous barrier surface free energy reduces, and promotes liquid-drop contact angle to increase, thereby reduce drop, from the Wenzel state, to the Cassie state, changes required critical pressure.
The present invention's microporous barrier used is nylon-microporous membrane, polysulfones microporous barrier, micropore CAM or high molecule micropore material.
The present invention's surface modification method used includes but not limited to CF
4cement Composite Treated by Plasma, the self assembly of fluorine-containing low-surface-energy material surface, sol-gal process.
The present invention's external pressure source of the gas used includes but not limited to the nitrogen stabilization pressure source.
Beneficial effect: by the method for the invention, we at room temperature utilize low force Cassie state effect to realize the microporous barrier wettability modification:
(1) by the inventive method, under the low pressure effect, change the drop on microporous barrier surface into the Cassie state by the Wenzel state, induce the microporous barrier surface to realize super-hydrophobic effect.
(2) by the inventive method, the surface modifying methods such as using plasma are modified the microporous barrier surface, reduce the microporous barrier surface free energy, and after modification, microporous barrier surface drop reaches the critical pressure reduction that super-hydrophobicity changes.
(3), by the inventive method, on the microporous barrier surface, low force Cassie state drop has significantly anti-stick stagnant and dewetting feature.
The present invention utilizes low force Cassie state effect to change the method for microporous barrier wetability, for designing the new structure super hydrophobic surface, provides a kind of new approach.With general super hydrophobic surface, compare, this novel pressure induces super-hydrophobic microporous barrier surface to reduce the degree of dependence to low-surface-energy material and surperficial micron/nano fine structure, reduce surface super hydrophobic effect inefficacy probability when externally pressure and surface fine structure are damaged, there is wide application prospect.
The accompanying drawing explanation
Fig. 1 is a kind of process of utilizing low pressure to induce the microporous barrier wettability reversal of the embodiment of the present invention;
Fig. 2 is anti-stick stickiness figure when in Fig. 1, microporous barrier surface water droplet is pressure pressure Cassie state;
Fig. 3 is kinetic characteristic figure when in Fig. 1, microporous barrier surface water droplet is pressure pressure Cassie state.
The specific embodiment
Below in conjunction with accompanying drawing and embodiment, the present invention is described in further detail, it is pointed out that the following stated embodiment is intended to be convenient to the understanding of the present invention, and it is not played to any restriction effect.
Embodiment 1:
In the present embodiment, microporous barrier adopts Millipore NY11 nylon-microporous membrane, and its micropore size is 11 μ m.
After being arranged on voltage stabilizing film fixed platform by Millipore NY11 nylon-microporous membrane, utilize set screw that voltage stabilizing film fixed platform is fixed on the optics contact angle measurement.After reconciling film fixed platform and contact angle measurement level, progressively increase the source of stable pressure atmospheric pressure, and record the water droplet form on this microporous barrier surface, obtain Fig. 1.After this microporous barrier both sides relative pressure reaches 288Pa, microporous barrier surface water droplet changes pressure into by the Wenzel state forces the Cassie state, as shown in Figure 1.Now, microporous barrier shows good water resistant and drips viscosity property, and as shown in Figure 2, and water droplet shows excellent locomitivity on this microporous barrier surface, as shown in Figure 3.
Embodiment 2:
In the present embodiment, microporous barrier is identical with the microporous barrier in embodiment 1, all adopts Millipore NY11 nylon-microporous membrane, and its micropore size is 11 μ m.Concrete grammar is substantially the same manner as Example 1, and difference is to adopt CF
4plasma carries out finishing to this microporous barrier, specific as follows:
At first, adopt CF
4plasma carries out finishing to Millipore NY11 nylon-microporous membrane, reduce the microporous barrier surface free energy, detailed process is: by the vacuum chamber of the ex vivo treatment instrument such as microporous barrier is fixed on, regulating the vacuum chamber operating pressure is 20Pa, power 75W, processing time 30min.Then, the microporous barrier after modification is arranged on voltage stabilizing film fixed platform, its pressure Cassie state critical pressure is 164Pa after measured.Then, after being arranged on voltage stabilizing film fixed platform by the microporous barrier after modification, utilize set screw that voltage stabilizing film fixed platform is fixed on the optics contact angle measurement.After reconciling film fixed platform and contact angle measurement level, progressively increase the source of stable pressure atmospheric pressure, and record the water droplet form on this microporous barrier surface.After this microporous barrier both sides relative pressure reaches 164Pa, microporous barrier surface water droplet is forced the Cassie state by Wenzel state transistion pressure.Now, microporous barrier shows good water resistant and drips viscosity property, and water droplet shows excellent locomitivity on this microporous barrier surface.
Above-described embodiment has been described in detail technical scheme of the present invention and beneficial effect; be understood that and the foregoing is only specific embodiments of the invention; be not limited to the present invention; all any modifications of making in principle scope of the present invention and improvement etc., within all should being included in protection scope of the present invention.
Claims (5)
1. a method of utilizing low force Cassie state effect to change the microporous barrier wetability, it is characterized in that: at room temperature, utilize the relative pressure of 100～300Pa to induce drop on the microporous barrier that aperture is 10～100 μ m to be changed to the Cassie state by the Wenzel state, change microporous barrier interface wetting characteristics; The aperture of microporous barrier is larger, and the critical pressure that on microporous barrier, drop reaches the Cassie state from the Wenzel state is less.
2. the method for utilizing low force Cassie state effect to change the microporous barrier wetability according to claim 1, it is characterized in that: described microporous barrier is nylon-microporous membrane, polysulfones microporous barrier or micropore CAM.
3. the method for utilizing low force Cassie state effect to change the microporous barrier wetability according to claim 1 and 2, it is characterized in that: described microporous barrier carries out finishing through surface modifying method, free energy reduction, the liquid-drop contact angle on microporous barrier surface are increased, then at room temperature, utilize the relative pressure of 100～300Pa to induce drop on microporous barrier to be changed to the Cassie state by the Wenzel state, change microporous barrier interface wetting characteristics.
4. the method for utilizing low force Cassie state effect to change the microporous barrier wetability according to claim 3, it is characterized in that: described surface modification method is CF
4cement Composite Treated by Plasma, the self assembly of fluorine-containing low-surface-energy material surface or sol-gal process.
5. the method for utilizing low force Cassie state effect to change the microporous barrier wetability according to claim 4, is characterized in that: described CF
4plasma treatment procedure is: at first, by the vacuum chamber of the ex vivo treatment instrument such as microporous barrier is fixed on, adopt CF
4as working gas, regulating the vacuum chamber operating pressure is 10～50Pa, power 20～100W, processing time 1～30min.
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| CN102690128B (en) * | 2012-06-01 | 2013-07-31 | 大连海事大学 | Regulating device and method for super hydrophobic surface wettability |
| CN103693613B (en) * | 2013-12-27 | 2015-08-26 | 大连海事大学 | A kind of surface wettability regulation device of based thin film distortion and regulate and control method |
| CN108680464B (en) * | 2018-03-12 | 2020-08-07 | 北京理工大学 | Method for judging structure surface wet state transition pressure |
| CN111497365B (en) * | 2020-04-03 | 2021-07-06 | 武汉大学 | Hydrophobic material based on two-dimensional material modified micro-nano structure and preparation method and application thereof |
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| US20050147757A1 (en) * | 2004-01-07 | 2005-07-07 | Roh Il J. | Method for wetting hydrophobic porous polymeric membranes to improve water flux without alcohol treatment |
| EP1943027A1 (en) * | 2005-10-26 | 2008-07-16 | Ramot at Tel-Aviv University Ltd. | Method and device for wettability modification of materials |
| CN1810448A (en) * | 2006-03-02 | 2006-08-02 | 南京大学 | Method of improving surface hydrophobicity of polymer |
| US20090011222A1 (en) * | 2006-03-27 | 2009-01-08 | Georgia Tech Research Corporation | Superhydrophobic surface and method for forming same |
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