WO2007106212A1 - Molecular plasma deposition of colloidal materials - Google Patents
Molecular plasma deposition of colloidal materials Download PDFInfo
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- WO2007106212A1 WO2007106212A1 PCT/US2007/001103 US2007001103W WO2007106212A1 WO 2007106212 A1 WO2007106212 A1 WO 2007106212A1 US 2007001103 W US2007001103 W US 2007001103W WO 2007106212 A1 WO2007106212 A1 WO 2007106212A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
- A61L27/54—Biologically active materials, e.g. therapeutic substances
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/21—Acids
- A61L2300/214—Amino acids
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/252—Polypeptides, proteins, e.g. glycoproteins, lipoproteins, cytokines
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
- A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
- A61L2300/258—Genetic materials, DNA, RNA, genes, vectors, e.g. plasmids
Definitions
- the invention relates to an apparatus and process for using corona discharge to deposit colloidally suspended molecules onto substrate surfaces.
- the method is applicable to deposition of organic and inorganic compounds, particularly to proteins and related biological compounds of interest onto selected substrates with little or no loss of native structure or activity.
- IPD Ionic plasma deposition
- Corona discharge is a well-known phenomenon which has long been observed in nature and traditionally used in a number of commercial and industrial processes. It is currently used in ozone production, control of surface generated electrical charges and in photocopying. Electric corona discharge has also been used to modify surfaces, particularly for plastic articles to improve surface characteristics, as described in United States Pat No. 3,274,089.
- An electrostatic coating process involving a corona discharge of a liquid or powdered material is described as a coating method, U.S. Patent 4,520,754.
- a corona is generated when the potential gradient is large enough at a point in the fluid to cause ionization of the fluid so that it becomes conductive. If a charged object has a sharp point, the air around that point will be at a much higher gradient than elsewhere. Air near an electrode can become ionized (partially conductive), while regions more distant do not. When the air near the point becomes conductive, it has the effect of increasing the apparent size of the conductor. Since the new conductive region is less sharp, the ionization may not extend past the local region. Outside the region of ionization and conductivity, the charged particles slowly find their way to an oppositely charged object and are neutralized.
- Corona discharge usually involves two asymmetric electrodes; one highly curved, e.g., a needle tip or a small diameter wire, and one of low curvature, e.g., a plate, or a ground.
- the high curvature ensures a high potential around the electrode, providing for the generation of a plasma. If the geometry and gradient are such that the ionized region continues to grow instead of stopping at a certain radius, a completely conductive path may be formed, resulting in a momentary spark or a continuous arc.
- Coronas may be positive or negative. This is determined by the polarity of the voltage on the highly-curved electrode. If the curved electrode is positive with respect to the flat electrode a positive corona exists; otherwise the corona is negative. The physics of positive and negative coronas are strikingly different. This asymmetry is a result of the great difference in mass between electrons and positively charged ions, with only the electron having the ability to undergo a significant degree of ionizing inelastic collision at ordinary temperatures and pressures.
- Corona discharge systems have been used to activate chemical compounds, generally to deposit polymers and polymerizable monomers formed within a corona discharge onto surfaces as protective coatings; as described in United States Patent No. 3,415,683.
- a corona discharge reactor for chemically activating constituents of a gas stream; e.g. sulfur and nitrogen oxides and mercury vapor, is described in United States Patent No. 5,733,360.
- the reactor is designed to pulse generate a corona by applying high voltages pulses for up to 100 nanoseconds to a plurality of corona discharge electrodes.
- WO 2006/046003 describes several methods for coating substrates involving use of a plasma, including use of low pressure pulsed plasma to introduce monomers or monomers in combination with free radical initiators to initiate polymerization on a suitable substrate.
- An atmospheric pressure diffuse dielectric barrier discharge assembly is used into which an atomized liquid containing the monomers is introduced so that a coating material is formed from atomized drops of from 10 to 100 ⁇ m.
- An atmospheric pressure glow discharge plasma generating apparatus using radiofrequency energized electrodes is described in WO 03/084682.
- a plasma coating apparatus and method are described in WO 02/28548.
- Liquid or solid atomized coating forming materials are introduced into a plasma discharge at atmospheric pressure and are useful for organic coatings such as polyacrylic acid or perfluoro compounds in addition to silicon-containing monomers.
- Corona effects are not always considered beneficial and may in fact cause arcing, or the breakdown of the corona.
- the corona effect may be too strong to successfully only singly charge a complex molecule.
- molecules ionize at a higher level they may break apart and lose structural and functional properties.
- the present invention relates to a molecular plasma deposition method for non- destructively coating biological agents on substrate surfaces.
- the method employs a modified IPD apparatus utilizing electric fields and vacuum to lay down a biological coating on virtually any conductive surface, and many non-conductive surfaces.
- a corona plasma molecular discharge is generated from a highly charged conductive tip.
- the method is applicable to deposition of a wide range of organic and inorganic materials, which are dispersed as solutions or suspensions from the conductive tip.
- the method employs solutions or suspensions of the materials to be deposited. This allows a wide range of organic as well as inorganic materials to be used, including elements and compounds.
- the liquids are atomized through a small pointed orifice maintained at a high voltage so that an ionized plasma is dispensed from the orifice.
- the ionized plasma is directed into an evacuated chamber where an oppositely biased substrate is located, causing the material to be deposited where it becomes bonded to the surface of the substrate.
- An important feature of the method is the deposition of biologically active agents onto a surface with little or no alteration of structure or functional characteristics.
- the method is equally applicable to inorganic materials, elements and select compositions, which are not otherwise amenable to coating processes. Due in part to the wide range of materials that can be deposited by this method, the ability to modify or bio-engineer different surfaces is significantly expanded.
- the known characteristics of the corona effect under atmospheric conditions and the advantages of ionic plasma deposition (IPD) methods in coating processes have been used to develop a novel corona plasma deposition process and coating method.
- An important aspect of the invention is the ability to use a corona generated from a liquid or colloidal composition to deposit a coating consisting of only the desired component, without the solvent in which the material to be deposited is dissolved or dispersed.
- maintaining the original structural properties of a wide range of materials deposited from a corona generated molecular plasma was not expected, most notably as shown with a polypeptide enzyme, which maintained catalytic activity after the molecular plasma deposition. Atomic bonds are not broken during the deposition process, a factor in retaining activity and/or structural integrity of the deposited product.
- the process is carried out in part under atmospheric or partial pressure, and in part under vacuum.
- the deposition apparatus is designed to generate a corona from a solution or suspension introduced through a narrow electrified opening, such that a plasma is produced in front of a small aperture that opens into a vacuum chamber housing a substrate.
- the substrate is wired as an oppositely charged electrode on which the plasma particulates will deposit.
- the apparatus for molecular plasma deposition can be modified to accommodate a partial vacuum around the conductive tip where the corona is generated. This permits more efficient volatilization of the solvent suspending the dissolved or suspended material, so that only the material itself is drawn into the vacuum chamber housing to be deposited on the substrate and little if any solvent is present in the coating. This is necessary because, in biological applications, if the suspending solvent is also co-deposited, it may cause an adverse interaction with the deposited material. For example, if a protein that one desires to deposit on a medical implant device is dissolved in methyl alcohol, and deposited without volatilization of the alcohol before being placed in the body, the residual alcohol may cause serious physiological problems. Where little or no solvent is drawn into the chamber, it is convenient to generate the corona under atmospheric pressure conditions.
- the new method is a molecular plasma procedure for deposition of a biomolecule onto a substrate.
- a corona discharge plasma is generated under atmospheric or partial vacuum conditions from a liquid solution or suspension.
- the suspension is preferable colloidal suspension for materials that have low solubility in organic or aqueous solvents.
- Deposited materials may be an element, a compound, or any of a number of biomolecules.
- the liquid solution or suspension is ejected from a conductive point source at a high potential gradient and the resulting corona discharge is directed through an opening into an evacuated chamber where the ionized molecular plasma will be deposited onto a substrate which is maintained at an induced potential opposite from the relatively high potential at the point source where the corona is generated.
- the conductive tip or point from which the colloidal suspension is ejected provides a means for atomizing the solution or liquid suspension, so that there is ready formation of a corona discharge at the high voltage tip.
- a low or partial vacuum can also be used, preferably 100 mTorr or higher.
- the charged plasma then passes through a hole or orifice into an evacuated chamber; e.g., at 40 mT or less, housing a substrate held at a voltage substantially opposite to the voltage at the conductive tip.
- the ionized molecules in the corona plasma then deposit onto the ' substrate in the chamber, which is at a lower pressure than at the conductive tip where the corona is generated.
- the substrate is under vacuum, typically less than 100 mTorr, preferably 40 mTorr or lower, and that if the plasma corona is formed at a tip also under reduced pressure, the substrate must be in a reduced pressure atmosphere such that the plasma can be effectively drawn into the substrate housing and deposited onto the substrate.
- the vacuum around the substrate is typically in the range of 40 - 0.1 mTorr.
- the substrate must be oppositely biased in order to effect deposition from the ionized molecular plasma, which may be positive or negative depending on the material in th p ro11niHa1 mi ⁇ nension.
- the ions formed in the discharge may be positive or negative. This discharge will determine the bias of the substrate; e.g., if a positive corona is used, the substrate must be negatively biased.
- the amount of bias imposed on the substrate will depend on the substrate and on the area for deposition. In the examples provided herein, the substrates are approximately 4 cm 2 .
- the bias of the substrate is constant regardless of the size of the deposition; however, the larger the area, the higher is the current necessary to maintain constant voltage.
- Voltage applied to the substrate may range as high as 60 kV, which may be positively or negatively biased; i.e., opposite to the voltage at the conductive tip where the corona is generated. Typical voltages range from +15kV through -15kV. Where the substrate is grounded, the voltage will be zero at the substrate.
- the method relies in part on efficiently generating an ionized plasma. This is accomplished by atomizing a liquid solution or suspension of the material desired for deposition through a sharp orifice or tip. This is typically a small diameter tube or needle that is imposed with a high voltage.
- An exemplary high voltage on an 18 gauge metal needle with an inside diameter of approximately 0.83 mm, for example, may be about - .5000 volts.
- the voltage applied to the substrate is typically in the range of about 5000 or less volts or is zero if connected to ground.
- Yet another aspect of the invention is the ability to control the corona effect for more efficient processing; e.g., for engineering surfaces.
- the method takes advantage of the physics of the corona effect to deposit ionized material onto a substrate, so that the material is ionically or covalently bonded to a substrate surface. This is a fast, easy way to produce an adherent coating and to structure a surface using a non-destructive technique.
- the described apparatus can be used to effectively deposit a wide range of materials without significantly altering the physical, functional or chemical characteristics, by generating material into a corona plasma from a liquid solution or suspension.
- Materials such as proteins are preferably ionized from colloidal suspensions, due to their limited solubility in most solvents. Thymine, cytosine, adenine and guanine with respective water solubilities of 4.5g/L, insoluble, 0.5g/L and insoluble, are more efficiently deposited as aqueous suspensions. Almost any organic or inorganic material can be dissolved or suspended in some solvent or mixture of solvents.
- Materials include proteins, amino acids, peptides, polypeptides, nucleic acids and nucleic acid bases such as purines and pyrimidines, and the like.
- inorganic materials include compounds such as metals and metal oxides, e.g., copper oxide, elements, including carbon.
- biological and non-biological materials that can be prepared as a solution or liquid suspension will be suitable materials for deposition. While colloidal suspensions may be preferable for some biomolecules, microparticulate suspensions may also be suitable, depending on the material, thus creating ionized molecular plasmas from liquids containing micron- or larger sized particles.
- Examples of material that are preferably deposited from molecular plasmas generated from colloidal suspensions include, but are not limited to: DNA, RNA, graphite, antibiotics, growth factors, growth inhibitors, viruses, inorganic compounds, catalysts, enzymes, organic compounds, and elements.
- Catalase is one example of a polypeptide enzyme that can be deposited by this method without loss of catalytic activity.
- Other proteins expected to be deposited by this method without loss of biological activity include SNAP-tag fusion proteins, hAGT fusion proteins glucose binding protein, glutamine binding protein and lactate dehydrogenase.
- Oxidodreductases and oxidases such as glucose oxidase are also expected to be deposited without loss of activity.
- Nucleotide bases such as guanine, thymine, adenine, cytosine, and uracil are examples of DNA and RNA bases that can be deposited onto a substrate from a corona generated plasma.
- solutions and liquid suspensions that are suitable for deposition may be formulated from any of a number of aqueous or organic solvents, including pure water, alcohol and water/alcohol mixtures. Some materials may be prepared in less common solvents, such as DMSO or glycols. For preferred practice of the deposition procedure, one will select a solvent or combination of solvents in which the material can be dissolved or suspended, preferably as a colloidal suspension, and which does not give rise to problems such as toxic or explosive fumes.
- Biomolecules are intended to include compounds and agents that have some biological effect or use in the body and may include, without limitation, proteins, peptides, amino acids, nucleic acids and compounds having drug activity or related to drug activity. As used herein, biomolecules also include carbon and carbon based compounds and elements and compounds such as copper oxide that may be used as coating materials on medical devices.
- Colloidal particles are finely divided particles approximately 10 to 10,000 angstroms in size, dispersed within a continuous medium. The particles are not easily filtered and settle slowly over a period of time.
- Nano particles are about 100 nanometers or less in size.
- IPD Ionic Plasma Deposition
- a corona is produced by a process by which a current, perhaps sustained, develops from an electrode with a high potential in a neutral fluid, such as air, by ionizing the fluid to create a plasma around the electrode.
- the ions generated eventually transfer a charge to nearby areas of lower potential, or recombine to form neutral gas molecules.
- Voltage bias is the potential, relative to earth ground, at which substrate is held. Potential ranges from zero to 15,000 volts and can be positive or negative. The potential on the substrate for biasing depends on the potential of the corona and is typically equal and opposite of this potential. Voltage may be as high as 6OkV but more typically is in the range of 5-1OkV. Where the corona plasma is +5000 volts, bias voltage for the substrate will be -5000 volts, all relative to earth ground.
- substantial or substantially means that a range is intended, on the order of plus or minus ten percent and is not intended to be limited to an exact number; for example, substantial function may include different or less than original function.
- FIG. 1 is a sketch pf the molecular plasma deposition apparatus: vacuum chamber 1; high voltage power supply 2, substrate holder 3; substrate 4; high voltage power supply 5; needle 6; feeder tube to needle 7; orifice 15 into reservoir 8; colloidal liquid suspension 9.
- FIG. 2 is a sketch of a modification of the apparatus of FIG. 1 : vacuum chamber 1 ; high voltage power supply 2; substrate holder 3; substrate 4; high voltage power supply 5; needle 6; feeder tube 7; orifice 15 into reservoir 8; liquid suspension 9; secondary chamber 10; secondary chamber gas supply 11; secondary chamber gas supply line 12; pressure regulator 13; gas line from regulator 14..
- FIG 3 is a representation of the electric field equation for a point charge.
- the present invention takes advantage of the corona effect and the effect of corona discharge in creating a charged plasma that can be directed to a substrate surface.
- the basic apparatus is shown in FIG. 1 and FIG. 2.
- a high voltage of 5kV or higher is applied to the needle or other hollow bore, sharp pointed, conductive material.
- a solution or liquid suspension is passed through the hollow bore.
- the high electric field at the tip of the needle causes atomization of the liquid as the result of the corona effect.
- the molecules in the solution or suspension become charged, yet remain intact.
- the needle is positioned in front of a grounded, differentially pumped high vacuum system with a small hole in the chamber housing the substrate.
- the substrate is placed inside the evacuated chamber at a potential opposite or nearly opposite to that imposed oh the needle or is set to ground (zero).
- the charged molecules within the corona travel through the opening toward the substrate and become deposited or attached to the substrate, becoming ionically or covalently bonded.
- the entire apparatus is enclosed in an environmentally controlled chamber into which selected gases such as oxygen or nitrogen may be introduced; for example, if oxidation is desired, to control deposition rate, or to perform the deposition in an inert atmosphere. Mixtures of gases may be introduced, including other inert gases such as xenon, argon, helium or combinations of gases.
- gases such as oxygen or nitrogen
- the molecular plasma generation process can also be run at lower than atmospheric pressures, i.e., under reduced pressure, in the presence of gases other than atmospheric, ⁇ e.g., argon or oxygen background atmosphere).
- the pressure in the chamber housing the substrate must be lower so that the plasma discharge passes readily through the opening into the chamber housing the substrate, as shown in FIG. 1.
- the molecular plasma generation apparatus provides a system for producing a plasma discharge under atmospheric conditions by passing a liquid colloidal suspension 9 through a discharge needle 6 at a high voltage 5.
- the resulting atomized liquid forms an ionized plasma in the atmosphere.
- the plasma passes through an orifice 15 in the vacuum chamber 1 housing the substrate 4 on the substrate holder 3.
- a power supply 2 provides voltage to the substrate 4 at a voltage opposite to that provided by the power supply 5 to the discharge needle 6.
- FIG. 2 illustrates an alternative embodiment of a system for producing an ionized plasma discharge.
- a reservoir 8 feeds a solution or liquid suspension of the material 9 through an orifice 15 for deposition of the colloidal material on the substrate 4.
- the liquid is passed through the highly charged needle 6 from the power supply 5.
- the feeder and needle are housed in a second chamber 10 which can be pressure regulated by a pressure control 13 through the opening 14 into the secondary chamber.
- the atmosphere within the secondary chamber 10 can be modified from a gas container 1 1 having a conduit 12 passing through the regulator 13.
- the vacuum chamber 1 is maintained at a lower pressure than in chamber 10.
- the substrate 4 is biased using the power supply 2 at a voltage opposite to that supplied by power supply 5 to the needle 6.
- Liquid suspensions or solutions may be prepared in organic or inorganic liquids, which should not be toxic or flammable. Most materials are preferably prepared as aqueous solutions or may be prepared in organic acids such as acetic acid, propionic acid, halogen substituted acetic acid, oxalic acid, malonic acid and/or hydroxycarboxylic acids alone or with water. Liquid mixtures may include salts or organic/water miscible preparations. Examples of alcohols include ethanol, methanol, and ketones such as acetone, DMF, THF and methylethylketone. Amino acids, for example, may be water soluble at low concentrations but form colloidal suspensions at higher concentrations. Lysine and threonine are highly water soluble while tyrosine has a limited solubility of about 0.045g/100 ml at 25°C.
- Corona discharge of both the positive and negative variety is commonly characterized as ionization of a neutral atom or molecule in a region of strong electrical field typically in the high potential gradient near a curved electrode, creating a positive ion and a free electron.
- the electric field then separates and accelerates the charged particles preventing recombination and imparting each particle with kinetic energy.
- Energized electrons which have a much higher charge/mass ratio and so are accelerated to a higher velocity, may create additional electron/positive-ion pairs by collision with neutral atoms. These then undergo the same separating process, giving rise to an electron avalanche.
- Both positive and negative coronas rely on electron avalanches.
- FIG. 3 illustrates a typical point charge formed in a strong electrical field.
- a corona is a process by which a current, whether or not sustained, develops from an electrode with a high potential gradient in a neutral fluid, usually air.
- a neutral fluid usually air.
- the potential gradient is large enough at a point in the fluid, the fluid at that point ionizes and it becomes conductive.
- the air around that point will be at a higher gradient than elsewhere, and can become conductive while other points in the air do not.
- the air becomes conductive it effectively increases the size of the conductor. If the new conductive region is less sharp, the ionization may not extend past this local region. Outside of this region of ionization and conductivity, the charged particles slowly find their way to an oppositely charged object and are neutralized.
- Corona discharge usually involves two asymmetric electrodes, one highly curved, such as the tip of a needle, or a narrow wire, and one of low curvature, such as a plate, or the ground.
- the high curvature ensures a high potential gradient around one electrode inn order to effectively generate a plasma.
- Coronas may be positive or negative. This is determined by the polarity of the voltage on the highly-curved electrode. If the curved electrode is positive with respect to the flat electrode the corona is positive; if the electrode is negative, a negative corona exists. The physics of positive and negative coronas are strikingly different. This asymmetry is a result of the large difference in mass between electrons and positively charged ions, with only the electron having the ability to undergo a significant degree of ionizing inelastic collisions at standard temperatures and pressures.
- a negative corona is manifested as a non-uniform corona, varying according to the surface features and irregularities of the curved conductor. It often appears as tufts of corona at sharp edges, the number of tufts changing with the strength of the field.
- the form of negative coronas is a result of its source of secondary avalanche electrons. It appears a little larger than the corresponding positive corona, as electrons are allowed to drift out of the ionizing region, allowing the plasma to continue some distance beyond it.
- the total number of electrons and electron density is much greater than in the corresponding positive corona; however, the electrons are at a predominantly lower energy, owing to being in a region of lower potential-gradient. Therefore, while for many reactions the increased electron density will increase the reaction rate, the lower energy of the electrons means that reactions which require a higher electron energy may take place at a lower rate.
- a positive corona is manifests as a uniform plasma across the length of a conductor. It is often observed as a blue/white glow, although much of the emission is in the ultraviolet. The uniformity of the plasma is due to the homogeneous source of secondary avalanche electrons. With the same geometry and voltages, a positive corona appears somewhat smaller than the corresponding negative corona, owing to the lack of a non-ionizing plasma region between the inner and outer regions. There are many fewer free electrons in a positive corona, perhaps a thousandth of the electron density, and a hundredth of the total number of electrons, compared to a negative corona, with the exception of the area close to the curved electrode where electrons are highly concentrated. This region has a high potential gradient, causing the electrons to have higher energy. Most of the electrons in a negative corona are in outer, lower energy field areas.
- the positive corona is divided into two regions, concentric around the sharp electrode.
- the inner region contains ionizing electrons, and positive ions, acting as a plasma, the electrons avalanche in this region, creating many further ion/electron pairs.
- the outer region consists almost entirely of the slowly migrating massive positive ions, moving toward the uncurved electrode along with, close to the interface of this region, secondary electrons, liberated by photons leaving the plasma, being re-accelerated into the plasma.
- the inner region is known as the plasma region, the outer as the unipolar region.
- a negative corona is manifested as a non-uniform corona, varying according to the surface features and irregularities of the curved conductor. It often appears as tufts of corona at sharp edges, the number of tufts altering with the strength of the field.
- the form of negative coronas is a result of its source of secondary avalanche electrons.
- the negative corona appears a little larger than the corresponding positive corona, due to drifting of the electrons from the ionizing region, so that the plasma continues some distance beyond it.
- the total number of electrons, and accordingly the electron density is much greater than in the corresponding positive corona.
- the electrons are lower energy that those in a positive corona because they are in a region of lower potential-gradient.
- Negative coronas are more complex than positive coronas in construction. As with positive coronas, the establishing of a corona begins with an exogenous ionization event generating a primary electron, followed by an electron avalanche. [0066] The difference between positive and negative coronas is in the generation of secondary electron avalanches. In a positive corona the avalanches are generated by the gas surrounding the plasma region, the new secondary electrons traveling inward, while in a negative corona they are generated by the curved electrode itself, the new secondary electrons traveling outward.
- An additional structural feature of negative coronas is the outward drift of the electrons, where they encounter neutral molecules and may combine with electronegative molecules such as oxygen and or water vapor to produce negative ions. These negative ions are then attracted to a positive uncurved electrode, completing the 'circuit*.
- a negative corona can be divided into three radial areas, around the sharp electrode.
- high-energy electrons inelastically collide with neutral atoms and cause avalanches, while outer electrons, usually of a lower energy, combine with neutral atoms to produce negative ions.
- outer electrons usually of a lower energy
- electrons combine to form negative ions, but typically have insufficient energy to cause avalanche ionization. They remain part of a plasma owing to the different polarities of the species present, and the ability to participate in characteristic plasma reactions.
- In the outer region only a flow of negative ions and, to a lesser and radially-decreasing extent, free electron movement toward the positive electrode takes place.
- the inner two regions are known as the corona plasma.
- the inner region is an ionizing plasma, the middle a non-ionizing plasma.
- the outer region is known as the unipolar region.
- the corona principal has been used to create an approximately infinite electric field at the point of a sharp needle.
- the tip of the device is atomically sharp and closely approximates a point charge. This is because as r goes to zero, E approaches infinity. A corona effect is initiated at the tip of the device.
- Example 1 Apparatus for Molecular Plasma Deposition
- An exemplary apparatus includes a vacuum chamber with a small aperture, and a small bore, metallic needle connected to a tube connected to a reservoir holding a liquid suspension or solution of the material desired to be deposited.
- the reservoir is at atmospheric pressure.
- a power supply with the ability to supply up to 6OkV can be employed; however, as used in the examples herein, the voltage attached to the needle is typically -5000 volts to +5000 volts.
- a substrate inside the vacuum chamber is centered on the aperture with a bias from -6OkV through -6OkV, including ground.
- the apparatus is illustrated in FIG. 1.
- Example 2 Apparatus for Molecular Plasma Generation under Selected Environments
- the apparatus illustrated in FIG. 2 can be modified such that the needle, tube, and reservoir are disposed in an enclosure that excludes air, but allows for the controlled introduction of other gases.
- gases include argon, oxygen, nitrogen, xenon, hydrogen, krypton, radon, chlorine, helium, ammonia, fluorine and combinations of these gases.
- the apparatus shown in FIG. 2 can be optionally operated at a predetermined pressure above or below atmospheric pressure. While atmospheric pressure is generally preferred for generation of the plasma, reduced pressure up to about 100 mTorr may in some instances provide satisfactory depositions.
- This example illustrates deposition of a suspension of amino acids onto a gold rod.
- a colloidal suspension of a mixture of the amino acids glycine (solubility of 20 g/1 at 25 0 C), alanine (166.5 g/1), valine (88.5 g/1), leucine (24.26 g/1) and arginine (235.8 g/1) in water was deposited using the apparatus of Example 1 onto a gold covered rod, 1/8" in diameter and approximately 0.75 cm 2 .
- the power supply was attached to a 304 stainless steel 18 gauge needle and set at -5000 V.
- the gold substrate was set at a potential of 5000 V.
- the substrate was centered on the hole in the chamber and placed 5 cm from the hole.
- the vacuum chamber was pumped to 40 mTorr and the flow of the colloidal suspension was initiated. The deposition was carried out for 30 min.
- the coated rod was placed in a time-of-flight secondary ion mass spectrometer (TOF- SIMS) and the components were analyzed for composition. Results showed that the amino acids were deposited intact and ion ⁇ cally bonded to the substrate. Mass over charge calculations in conjunction with the time of flight spectrometry were used to calculate the masses of the incoming species. These calculations were used to interpret the spectra from the SIMS. The m/q data showed the amino acids being ejected intact from the surface.
- TOF- SIMS time-of-flight secondary ion mass spectrometer
- a colloidal suspension of graphite powder in isopropyl alcohol (1Og/ 100ml) was deposited onto an aluminum oxide substrate using the apparatus shown in FIG. 1.
- the power supply was attached to a 304 stainless steel 18 gauge needle and set at - 5000V.
- the aluminum oxide substrate was connected to ground.
- the substrate was centered on the hole in the chamber and placed 5 cm from the hole.
- the vacuum chamber was pumped to 40 mTorr and the flow of the colloidal suspension was initiated.
- the deposition was carried out for 30 minutes.
- the substrate was removed from the chamber and a simple ohm meter resistance test performed. Resistance of the substrate changed from infinite to 1 ohm over the 30 min deposition period.
- a colloidal suspension of copper oxide powder in water (1Og/ 100ml) was prepared.
- the high voltage power supply was attached to a 304 stainless steel, 18 gauge needle set at -10,000V.
- the substrate was 304 stainless steel and set at a potential of 5000 V.
- the substrate was centered and placed 5 cm from the hole in the chamber.
- the chamber was pumped to 40 mTorr and the flow of the colloidal suspension initiated.
- the deposition onto the substrate was allowed to proceed for 10 minutes.
- the substrate was removed from the chamber and a simple tape test showed good adhesion of the deposited copper oxide. Good adhesion between the substrate and the copper oxide were confirmed by repeating the tape test and by observing that after sonicating the coated sample for 10 min there was no evidence of flaking or sloughing.
- Example 7-Molecular Plasma Deposition of RNA and DNA Bases A colloidal suspension of guanine, adenine, cytosine, uracil and thymine in water (each at 5g/100ml) was deposited onto gold covered rod having a surface of approximately 0.75 cm 2 area, l/8"diameter, using the apparatus of Example 1.
- the power supply was attached to a 304 stainless steel 18 gauge needle and set at -5000V.
- the gold substrate was set at a potential of 5000 V.
- the substrate was centered on the hole in the chamber and placed 5 cm from the hole.
- the vacuum chamber was pumped to 40 mTorr and the flow of the colloidal suspension was initiated. The deposition was carried out for 30 min.
- the coated rod was placed in a time-of-flight secondary ion mass spectrometer (TOF- SIMS) and the components were analyzed for composition. Results showed that the DNA bases were deposited intact and ionically bonded to the substrate. Mass over charge calculations in conjunction with the time of flight spectrometry were used to calculate the masses of the incoming species.
- TOF- SIMS time-of-flight secondary ion mass spectrometer
- the high voltage power supply was attached to a 304 stainless steel, 18 gauge needle set at -5000V.
- the substrate was an aluminum oxide disk 1 A" thick by 1.5" in diameter, having an area of approximately 11 sq cm and set at a potential of 5000 V.
- the substrate was centered and placed 5 cm from the hole in the chamber.
- the chamber was pumped to 40 mTorr and the flow of the colloidal suspension initiated.
- the deposition onto the substrate was allowed to proceed for 10 minutes.
- the substrate was removed from the chamber and the sample was placed in a 5% solution of hydrogen peroxide.
- the results showed the catalysis of the hydrogen peroxide by the catalase, producing bubbling of oxygen from the surface, showing that the enzyme remained intact throughout the deposition process.
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Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
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EP07748926A EP1993627A4 (en) | 2006-02-27 | 2007-01-16 | Molecular plasma deposition of colloidal materials |
MX2008010696A MX2008010696A (en) | 2006-02-27 | 2007-01-16 | Molecular plasma deposition of colloidal materials. |
JP2008556315A JP2009528155A (en) | 2006-02-27 | 2007-01-16 | Molecular plasma deposition of colloidal materials. |
IL193463A IL193463A0 (en) | 2006-02-27 | 2008-08-14 | Molecular plasma deposition of colloidal materials |
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US77710406P | 2006-02-27 | 2006-02-27 | |
US60/777,104 | 2006-02-27 |
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WO2007106212A1 true WO2007106212A1 (en) | 2007-09-20 |
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PCT/US2007/001103 WO2007106212A1 (en) | 2006-02-27 | 2007-01-16 | Molecular plasma deposition of colloidal materials |
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EP (1) | EP1993627A4 (en) |
JP (1) | JP2009528155A (en) |
CN (1) | CN101389365A (en) |
IL (1) | IL193463A0 (en) |
MX (1) | MX2008010696A (en) |
WO (1) | WO2007106212A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012080835A2 (en) | 2010-12-13 | 2012-06-21 | Enbio Limited | Implantable medical devices |
WO2017136334A1 (en) | 2016-02-01 | 2017-08-10 | Theradep Technologies Inc. | Systems and methods for delivering therapeutic agents |
US10946118B2 (en) | 2009-06-16 | 2021-03-16 | Theradep Technologies, Inc. | Wound healing device |
US11690998B2 (en) | 2017-10-31 | 2023-07-04 | Theradep Technologies, Inc. | Methods of treating bacterial infections |
Citations (3)
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US5102687A (en) * | 1988-11-23 | 1992-04-07 | Centre National De La Recherche Scientifique-C.N.R.S. | Process for surface treatment by plasma of a substrate supported by an electrode |
US5849455A (en) * | 1994-12-16 | 1998-12-15 | Canon Kabushiki Kaisha | Plasma processing method and plasma processing apparatus |
US6131580A (en) * | 1998-04-17 | 2000-10-17 | The University Of Washington | Template imprinted materials by RFGD plasma deposition |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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DE3827631A1 (en) * | 1988-08-16 | 1990-02-22 | Hoechst Ag | SELF-SUPPORTING AREA WITH AT LEAST ONE STRUCTURED SURFACE |
JP4230170B2 (en) * | 2001-06-08 | 2009-02-25 | 株式会社半導体エネルギー研究所 | Method for manufacturing light emitting device |
EP1571904A2 (en) * | 2002-12-18 | 2005-09-14 | Ionic Fusion Corporartion | Ionic plasma deposition of anti-microbial surfaces and the anti-microbial surfaces resulting therefrom |
JP4119820B2 (en) * | 2003-11-14 | 2008-07-16 | 三菱重工業株式会社 | Plasma CVD apparatus and method for manufacturing photoelectric conversion apparatus |
GB0410749D0 (en) * | 2004-05-14 | 2004-06-16 | Dow Corning Ireland Ltd | Coating apparatus |
JP4628696B2 (en) * | 2004-06-03 | 2011-02-09 | 東京エレクトロン株式会社 | Plasma CVD equipment |
JP4289246B2 (en) * | 2004-07-21 | 2009-07-01 | 富士電機システムズ株式会社 | Thin film forming equipment |
GB0507537D0 (en) * | 2005-04-14 | 2005-05-18 | Univ Durham | Protein resistant surfaces |
-
2007
- 2007-01-16 WO PCT/US2007/001103 patent/WO2007106212A1/en active Application Filing
- 2007-01-16 EP EP07748926A patent/EP1993627A4/en not_active Withdrawn
- 2007-01-16 JP JP2008556315A patent/JP2009528155A/en active Pending
- 2007-01-16 MX MX2008010696A patent/MX2008010696A/en not_active Application Discontinuation
- 2007-01-16 CN CNA200780006725XA patent/CN101389365A/en active Pending
-
2008
- 2008-08-14 IL IL193463A patent/IL193463A0/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5102687A (en) * | 1988-11-23 | 1992-04-07 | Centre National De La Recherche Scientifique-C.N.R.S. | Process for surface treatment by plasma of a substrate supported by an electrode |
US5849455A (en) * | 1994-12-16 | 1998-12-15 | Canon Kabushiki Kaisha | Plasma processing method and plasma processing apparatus |
US6131580A (en) * | 1998-04-17 | 2000-10-17 | The University Of Washington | Template imprinted materials by RFGD plasma deposition |
Non-Patent Citations (1)
Title |
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See also references of EP1993627A4 * |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10946118B2 (en) | 2009-06-16 | 2021-03-16 | Theradep Technologies, Inc. | Wound healing device |
WO2012080835A2 (en) | 2010-12-13 | 2012-06-21 | Enbio Limited | Implantable medical devices |
US8771782B2 (en) | 2010-12-13 | 2014-07-08 | Enbio Limited | Implantable medical devices |
EP3162386A1 (en) | 2010-12-13 | 2017-05-03 | TheraDep Technologies, Inc. | Implantable medical devices |
WO2017136334A1 (en) | 2016-02-01 | 2017-08-10 | Theradep Technologies Inc. | Systems and methods for delivering therapeutic agents |
US11772126B2 (en) | 2016-02-01 | 2023-10-03 | Theradep Technologies Inc. | Systems and methods for delivering therapeutic agents |
US11690998B2 (en) | 2017-10-31 | 2023-07-04 | Theradep Technologies, Inc. | Methods of treating bacterial infections |
Also Published As
Publication number | Publication date |
---|---|
EP1993627A4 (en) | 2012-10-10 |
EP1993627A1 (en) | 2008-11-26 |
MX2008010696A (en) | 2008-11-14 |
IL193463A0 (en) | 2009-05-04 |
JP2009528155A (en) | 2009-08-06 |
CN101389365A (en) | 2009-03-18 |
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