Bilayer processes scheme

This section deals with process technologies associated with the bilayer process. Particular emphasis will be given to the development of an all-dry processing scheme including dry development and dry deposition of the Ag-compound sensitizing layer. 

Figure 3.37. Bilayer negative dry-development scheme. The SEM shows the final image obtained by the bilayer process with a Perkm-Elmer M500 in the UV-2 mode. Reproduced with permission from reference 127. Copyright 1985 Society of Plastics Engineers.)...

Fig. 3 Processing scheme of lithography with bilayer (left) and Si-CARL (right) photoresist. (View this art in color at www.dekker.com.)...

Shown in Figure 1 are the principal schemes for micelle and liposome formation and loading with various reporter moieties that might be covalently or noncovalently incorporated into different compartments of these particulate carriers. Although micelles may be loaded with a contrast agent only into the core in the process of micelle assembly, liposomes may incorporate contrast agents in both the internal water compartment and the bilayer membrane. 

Fig. 52a-c. Scheme of the fusion process of giant liposomes and the formation of small unilamellar vesicles (SUV) at the interface, a) lipid bilayers in contact b) pores generated by electric breakdown and lipid reorientation forming SUVs c) reconstitution of lipid membranes formation of a fused giant liposome and SUVs . 

Fig. 10 Example of a contact-killing and microbe-releasing surface. The scheme shows the design of a two-level dual-functional antibacterial coating containing both quarternary ammonium salts and silver. The coating process begins with LbL deposition of a reservoir made of bilayers of PAH and PAA. (A) Cap region made of bilayers of PAH and SiC>2 nanoparticles (NP) is added to the top. (B) The SiC>2 nanoparticle cap is modified with a quarternary ammonium silane (QAS) PEM polyelectrolyte multilayer. (C) Ag+ is loaded into the coating using the available unreacted carboxylic acid groups in the LbL multilayers. Scheme was reproduced from [138]...

The molecular model of amphiphile bilayers can also be used for describing the process of hole nucleation by the classical nucleation scheme [408,409] as resulting from a series of bimolecular reactions characterised by the nucleation rate J (s 1) which is the frequency with which the / -sized nucleus holes become supemucleus holes of size / +1. For steady-state nucleation, J is known to be [408,409]... 

In the previous decade, RS -initiated cis/trans isomerization of the double bonds in membrane phospholipids, producing trans-isomers of unsaturated fatty acid moieties, had been demonstrated (Scheme 1). RS radicals derived from biologically relevant thiols such as glutathione (GSH) and cysteine (CysH) initiate the isomerization process that results in the incorporation of trans-isomtrs into membranes to give more rigid packing of the bilayer. 

Transfer of calcium cations (Ca2 + ) across membranes and against a thermodynamic gradient is important to biological processes, such as muscle contraction, release of neurotransmitters or biological signal transduction and immune response. The active transport can be artificially driven (switched) by photoinduced electron transfer processes (Section 6.4.4) between a photoactivatable molecule and a hydroquinone Ca2 + chelator (405) (Scheme 6.194).1210 In this example, oxidation of hydroquinone generates a quinone to release Ca2+ to the aqueous phase inside the bilayer of a liposome, followed by reduction of the quinone back to hydroquinone to complete the redox loop, which results in cyclic transport of Ca2 +. The electron donor/acceptor moiety is a carotenoid porphyrin naphthoquinone molecular triad (see Special Topic 6.26). 

The kinetics of carrier-mediated cation transport through bilayer membranes have also been investigated. Figure 18 shows a scheme of four different processes,... 

Phenolic resists can be silylated also after wet development with aqueous base [463,464]. In the silicon-added bilayer resist (SABRE) process (Fig. 165), a di-azoquinone/novolac resist is coated on a top of a planarizing layer and imaged in the conventional fashion by UV exposure and aqueous base development [463]. The phenolic polymer remaining in the unexposed area after development is silylated in a gas phase or in solution to provide 02 RIE resistance for dry etching of the underlying layer [463,464]. This bilayer scheme takes advantage of high contrast aqueous base development to produce square resist profiles, which are then converted to a well-defined Si mask by silylation for 02 RIE pattern transfer. Thus, a poor silylation contrast sometimes encountered... 

Many amphiphiles exist naturally and play a major role in biological processes. Phospholipids (Scheme 2) are of especial importance because their twin lipophilic groups allow them to form bilayers, so that they are the building blocks of membranes and they, and similar amphiphiles, will form vesicles in water [14,16,17]. 

As a new type of electron relay, which is able to penetrate lipid membranes, we tested menaquinone (MQ, Fig. 7). Compounds of this type were not utilized earlier for artificial vesicle-based systems. However, these mimick the functioning of the Z-scheme of natural plant photosynthesis (see Figs 9 and 12). Indeed, the activity of MQ in the redox processes in a lipid bilayer membrane was revealed. However, the quantum yield of the transmembrane electron transfer from a CdS nanoparticle in the inner cavity to a CdS nanoparticle on the outer membrane surface with the participation of MQ appeared to be very low and did not exceed 0.2-0.4%. 

For NR nanocomposite filled with silica, it has always been known that the hydrophilicity-hydrophobicity issue is a challenge since silica is hydrophilic and NR is hydrophobic. The usual method to overcome this issue is by adding coupling agent. In 1987 Wu and coworkers introduced admicellar polymerization where a thin polymeric film will be formed on the silica s surface. This process yields a thin film of polymer on the silica which can further enhance the adhesion between the surfaces of silica and rubber. The steps involved in admicellar polymerization are outlined in Scheme 7.7. In principle, a bilayer of surfactant, i.e. the admicelle, is first formed on the surface of the silica. Monomer will then penetrate the admicelle, i.e. the adsolubilization of monomer. Upon addition of initiator to the reaction system, in situ polymerization occurs in the admicelles. Finally, the surfactant is removed by washing with water and an ultrathin polymer layer is formed on the surface of the silica. The polymerization of the monomer in the admicelles can be induced by thermal process, chemical initiators or radiation. ... 

In this study, we use the same simulation scheme to study the behavior of these model amphiphiles in the presence of a liquid/vapor interface. This is quite feasible since Lennard-Jones particles are known to exhibit liquid/ vapor coexistence [16]. In short, we observe a highly regulated self-assembly process leading to the formation of one or more well-formed bilayers in the liquid phase amphiphiles not included in the bilayers are dispersed in the vapor phase. In this paper, we report on this phenomenon, and examine how the size and overall eoncentration of amphiphiles govern the development and characteristics of the bilayers formed. We also show that bilayer formation can be suppressed if the geometry of the amphiphiles is altered, as is predicted by simple packing arguments. 

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