Hydrophobic surfaces, enhancement plasma polymers

Avseenko et al. (2001) immobilized antigens onto aluminum-coated Mylar films by electrospray (ES) deposition. Various surface modifications of the metallized films were studied to determine their abilities to enhance sensitivity. The plastic surfaces were firsf cleaned by plasma discharge treatment, followed by coating with proteins (BSA and casein) or polymers such as poly (methyl methacrylate) or oxidized dextran, or they were exposed to dichlorodimethyl silane to create hydrophobic surfaces. Protein antigen was prepared in 10-fold excess sucrose and sprayed onto the surfaces to form arrays with spot diameters between 7 and 15 pm containing 1 to 4 pg protein. 

Parylene N to smooth surface materials has been reported with the application of plasma depositions [13,14]. It was reported that excellent adhesion of Parylene C coating to a cold-rolled steel surface was achieved using plasma polymer coatings, in turn giving rise to corrosion protection of the metal [15]. Another major deficiency of Parylene C is its poor painting properties when paint is applied on a Parylene C film, due to its extremely hydrophobic surface. Because of this, surface modification of Parylene films is necessary to enhance their adhesion performance with spray primers. 

The reference ISFET can be modified by chemically reacting the SiOH groups with trimethoxysilanes [7]. An alternative method involves deposition of a hydrophobic polymer on the surface, for example by thermal deposition of parylene [85]. These layers tend to be chemically bound to the SiOH surface, leading to enhanced stability and long lifetimes. Also the layers are very thin, which is essential because of decreased electrical sensitivity as the insulator thickness increases [9]. For ion-blocking layers, a stable attachment has been realized by plasma deposition [86,87]. 

Protein adsorption onto intrinsically repellent materials is enhanced by a brief plasma treatment that chemically and physically alters the surface properties. Stencil-assisted plasma oxidation of inherently hydrophobic polymers (e.g., PDMS... 

We, therefore, developed a new method for enhancing albumin adsorption, a method that may provide indefinite protection against thrombogenesis and cell adhesion. The method takes advantage of the hydrophobic affinity and reversible dynamic binding of albumin from plasma to C18 alkyl residues that are, in turn, covalently bound onto various polymer surfaces. 

Flat porous poly(vinylidene fluoride) hydrophobic membranes were used for the removal and the recovery of CO2 from the emission sources (Lin et al. 2009b). Methane plasma treatment enhanced the hydrophobicity of this polymer—the elemental F/C ratio at the surface increased and was almost twice as big as the starting value. The water contact angle increased from 132° for virgin polyvinylidene fluoride (PVDF) to 155° after plasma treatment. Some effects of etching were observed, especially for longer plasma treatment time. 

As mentioned previously, the surface conditions of the substrate are important when solutions such as PEDOTrPSS or other inks are coated. Basically, it is not easy to coat aqueous based PEDOTrPSS onto the hydrophobic polymer substrate. Therefore, various techniques can be applied to modify the surface of the substrate, e.g. plasma treatment and treatment with various chemicals such as primers or coating promoters. The surface energy can be divided into the disperse energy and polar energy. The sum of the two terms is the total surface energy. For example, the surface energy of the substrate can be enhanced by O2 plasma. The surface energy is increased with respect to the treatment time with O2 plasma, as shown in Table 13.4. 

For the bottom-up approach, the rough surface can be created by polymerization of a monomer via plasma-enhanced CVD technique or electropolymerization. Surface morphology is sensitive to the polymerization condition. Usually, the roughness is random with a hierarchical particulate or fibrous structure. When a hydrophobic monomer is used, the surface will be superhydrophobic after polymerization. Figure 4.2 la shows a 10 x 10 pm AFM image of a PEC VD polymer film polymerized from perfluorooctyl acrylate. The surface comprises nanospherical particles and exhibits very high water repeUency with 0a/0r at 168°/165° [67]. Similarly, electropolymerization of 3,4-ethyleneoxythiathiophene derivatives also yield superhydropho-... 

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