Photo-patterning

TPAs bearing cross-linkable oxetane functionalities (52) (Scheme 3.20) has been developed [95,96], This material can be easily photo-patterned by exposure to a very short wavelength UV light source to form a patterned and insoluble HTL. Similar photo-cross-linkable HTMs based on side-chain acrylate or styryl functional groups have been synthesized (53,54) [97]. A series of spiro-linked and photo-cross-linkable HTMs have been patented by the Canon group [98]. 

Direct Patterning of Photosensitive Polyimides. Photosensitive polyi-mides (PSPIs) are recently developed materials that can be directly photo-patterned like a negative photoresist (80,85,88,146-148). The most common PSPIs are polyamic acids that have been esterified with photoreactive alcohols and combined with photoinitiators to form a polymer that will crosslink under exposure to UV radiation and become insoluble. The unexposed material is selectively dissolved in a developer solution, and the patterned film is then cured to convert the cross-linked polyamic acid to a polyimide and drive off the cross-linking groups. 

HeLa, embryonic mouse fibroblasts, human epithelial cells pCP of proteins or PEG, photo- patterning through light-induced crosslinking of FN-benzophenone 2007 [89]... 

A direct solution to this problem would be a buffer layer between the pentacene channel layer and parylene passivation layer. Given that poly(vinyl alcohol) (PVA) has been used as a photo-patternable etch mask for pentacene, it can also work as this buffer layer. After PVA patterning of the pentacene TFT, 1 pm parylene was vapor deposited and patterned by standard photolithography and RIE dry etching. The TFT characteristics were measured before and after the parylene passivation. 

Photolithographic methods, which play a key part in the fabrication of semiconductors, are potential candidates for the photo-patterning of small enzyme-immobilized membranes on a FET at its wafer stage. Ion-sensing FET devices with neutral carrier membranes sensitive to alkaline and alkaline earth metal... 

A self-assembled monolayer of 4-cyano-4 -(10-thiodecoxy)stilbene on a Au-electrode was shown to have different hydrophobicities. In the trans-(18a) and cis- (18b) isomeric states (Figure 7.25). When the monolayer is in the CIS-State (18b), the polar cyano-groups are hidden in the monolayer and the hydrophobic spacers are exposed to the solution, thus providing the hydrophobic properties of the interface. After irradiation of the monolayer (X > 350 nm), the ds-stilbene units are photoisomerized to the fmws-state (18a), and the polar cyano-groups are mainly exposed to the solution. In this case, the interface becomes more hydrophilic, and the monolayer displays markedly different wetting properties. This difference allows the photo-patterning of the surface. ... 

Conditions of polymerization like temperature ( 7°C or 40°C what means below or above the phase transition temperature in pure water), nature of solvent (water or water/ethanol 50/50 mixture to use hydrophilic or more hydrophobic photo initiators), amount of cross-linker and monomer concentration can be varied to investigate the effect of reaction conditions on the swelling behaviour, phase transition temperature and morphology. Photo patterning of hydrogels can be done in the presence of an adhesion promoter on glass substrate (Singh et al. 2006). 

Molecular-level fabrication of a conducting polymer matrix is an important hurdle to constructing molecular devices. Three approaches have been demonstrated (i) electrochemical polymerization of Langmuir-Blodgett (LB) multilayers, (ii) photo-patterning of conducting polymers [9], and (iii) depth profile control of conducting polymer multilayers. These are discussed in turn. 

The electrochemical fluorescence switching from a patternable poly(l,3,4-oxadiazole) thin film has been assessed [46]. The high solubility of the polymers enables a simple fabrication of an electrochemical cell, which shows a reversible fluorescence switching between dark and bright states with a maximum on/off ratio of 2.5 and a cyclability longer than 1000 cycles. The photochemical cleavage of the oxadiazole in the poly(arylene-l,3,4-oxadiazole) allows a photo-patterning of the film upon exposure to UV source. 

Photo-patterning is a process used in IC and microfabrication to selectively remove parts of a thin film (photoresist). It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical on the substrate. A series of chemical treatments then engrave the exposure pattern into the material underneath the photoresist. 

We have described thiol derivatives with photo-functionalities and presented schematic illustrations of the photoelec-trochemicaUy active SAMs and multilayers constructed on the electrode surfaces as many as possible in this section. However, since there are a large number of studies on wide range of photoactive alkylthiol SAM-modified electrodes, we cannot review all the important subjects in this section such as photo-patterning [152-156] and nonlinear optical properties [157,158]. Instead we have listed many references for the interested readers. 

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