Aqueous electrophoretic deposition

Abstract

From an environmental, safety and economic perspective water should be the solvent of choice for electrophoretic deposition under industrial circumstances. However, because of the electrolytic decomposition of water, the majority of EPD is carried out in non-aqueous solvents. Approaches of the art for aqueous deposition involve the separation of the reaction and deposition front by means of a membrane, the use of palladium electrodes to absorb the formed hydrogen, addition of chemicals to suppress the electrolysis reaction, or lowering voltages below the threshold for water electrolysis. With the first two solutions, the production of coatings is impractical since the deposit is not formed on the electrode, or the electrode material is not suitable since the substrate is usually prescribed by the application. The use of specialty chemicals is expensive and difficult to control. Low voltages have been used to form high quality deposits from aqueous systems but they display very low deposition rates, which are not attractive from an economical perspective. Present invention provides a system and a means for which high voltages can be used in the electrophoretic deposition from aqueous suspensions without decomposition of water at satisfying deposition rates. It shows that the deposits obtained show a high green density with excellent surface quality.

1 - 53 . (canceled) 
     
     
         54 . A coating process comprising the steps of: immersing an electrode or porous substrate placed in front of an electrode in an aqueous medium comprising charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles and subjecting said charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles in an aqueous medium to (asymmetric) unbalanced alternating current (UAC) electric fields, having a frequency and a positive and negative part each having an amplitude and a duration, to deposit electrophoretically said charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles onto said electrode or porous substrate placed in front of an electrode, wherein said amplitude of said unbalanced alternating current (UAC) electric field differs significantly for the positive and negative part, while maintaining an applied signal whose net integral over one period, i.e. average potential, is lower in absolute value than 4V. 
     
     
         55 . The coating process of  claim 54 , wherein said duration of the negative and positive part of said UAC electric fields differ in addition to said amplitude of the negative and positive part of said UAC electric fields while the overall integral over one period, i.e. average potential, is lower in absolute value than 4V. 
     
     
         56 . The coating process of  claim 54 , wherein said charged or self-charging compounds or organic or metallo-organic molecules are dissolved in said aqueous medium. 
     
     
         57 . The coating process of  claim 54 , wherein the charged or self-charging compounds or organic or metallo-organic molecules are incorporated in colloidal particles in suspension in the aqueous medium or in an aqueous slurry. 
     
     
         58 . The coating process of  claim 54 , wherein the charged or self-charging compounds or organic or metallo-organic molecules are incorporated in charged or self-charging solid particles that stabilize an emulsion. 
     
     
         59 . The coating process of  claim 54 , wherein the charged or self-charging compounds or organic or metallo-organic molecules are in or from living or killed cells, cell organelles or cell components. 
     
     
         60 . The coating process of  claim 54 , wherein the charged compounds or organic or metallo-organic molecules are amino acids, nucleic acid molecules (e.g., RNA, DNA, oligonucleotides, polynucleotides, mixed polymers, peptide nucleic acid, and the like), peptides (e.g., polyaminoacids, polypeptides, proteins and the like). 
     
     
         61 . The coating process of  claim 54 , wherein the charged or self-charging compounds or organic or metallo-organic molecules are macromolecules. 
     
     
         62 . The coating process of  claim 54 , wherein the charged or self-charging compounds or organic or metallo-organic molecules are a bio-active agent. 
     
     
         63 . A coating process comprising the steps of: immersing an electrode or porous substrate placed in front of an electrode in an aqueous medium comprising charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles and subjecting said charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles in an aqueous medium to (asymmetric) unbalanced alternating current (UAC) electric fields, having a frequency and a positive and negative part each having an amplitude and a duration, to deposit electrophoretically said charged, partially charged or self-charging organic or metallo-organic molecules or colloidal particles onto said electrode or porous substrate placed in front of an electrode, wherein said amplitude of said unbalanced alternating current (UAC) electric field differs significantly for the positive and negative part, while maintaining an applied signal whose net integral over one period, i.e. average potential, is lower in absolute value than 4V used to form smooth deposits with no visible defects having a surface with a Ra of 10 nm to 50 μm. 
     
     
         64 . The coating process according to  claim 63  to form a deposit with green density >30%. 
     
     
         65 . The coating process according to  claim 63  to produce a device, instrument, a medical prosthesis, an orthopaedic implant, dental endodontic or dental implant. 
     
     
         66 . The coating process according to  claim 63  to coat a medical prosthesis, an orthopaedic implant, dental endodontic or dental implant; or coat or paint a device or instrument. 
     
     
         67 . The coating process according to  claim 63  to immobilise charged or self-charging compounds or organic or metallo-organic molecules from an aqueous medium in a patterned structure on a substrate. 
     
     
         68 . The coating process according to  claim 63  to produce a food or feed. 
     
     
         69 . The coating process according to  claim 63  to produce a biocompatible implant. 
     
     
         70 . The coating process according to  claim 63  to form a deposit with an average thickness in the nm size range, in the micrometer scale, in the millimetre scale or in the centimetre scale. 
     
     
         71 . The coating process according to  claim 63  to coat components of a bioreactor. 
     
     
         72 . The coating process according to  claim 63  to produce monolithic objects, hollow objects, thin wall objects, membranes or wire for instance nanowires. 
     
     
         73 . The coating process according to  claim 63  to produce films of cationic or anionic polymers. 
     
     
         74 . The coating process according to  claim 63  to coat an implant, in particular an arterial or venal implant by a coating or layer with a compound selected from the group of consistence of polytetrafluoroethylene, polyethylene, polypropylene, polybutene, polyurethane, polyvinylpyrrolidone, polyethylene oxide, hyaluronic acid polymers, mixtures thereof and copolymers thereof. 
     
     
         75 . The coating process according to  claim 63  to coat a conductive substrate with organics such as monomers, precursors, hydrocarbons, functional hydrocarbons, macromolecules, oligosaccharides, polysaccharides, polymers (e.g. thermoplastic polymers, thermo curing polymers, biopolymers, alginates, carrageen or other algae derived polymers, kollicoat IR, or resins, oligomers some of which can be bioactive and others biocompatible.