Patterned and switchable surfaces for biomaterial applications

Chapter 1 - Introduction1.2.2. Soft lithographyCP is a soft lithography technique developed out of a need to pattern surfaceswithout the experimental difficulties and high costs of photolithography. Typically,this approach involves the once-off production of a mould, using photolithographicmethods, that is patterned as the negative of the design of interest. This mould is thenused to form a patterned stamp, typically composed of a crosslinked elastomericpolymer, like poly(dimethylsiloxane) (PDMS). The stamp is used to transfer apatterned image of an ‘ink’ molecule onto the desired substrate surface. Thereusability of the photomask and low cost of the PDMS stamp make this techniquean extremely cost effective and potentially high-throughput patterning alternative.Currently, this method is primarily used for the patterning of SAMs onto gold orsilanes onto glass or silica surfaces. Thus, CP suffers from a limited number ofsubstrate surfaces and ‘ink’ molecules [85].Zhang et al., [76] produced cell patterns using CP of SAMs. A (11-mercaptoundec-1-yl)-hexa-(ethylene glycol) was printed onto gold coated siliconusing a PDMS stamp with a topographical pattern. After SAM pattern transfer andwashing, the surface was exposed to an engineered peptide strand containing ananchoring cysteine residue, an alanine linker and a Arg-Ala-Asp-Ser (RADS) celladhesion motif linker group, which is based upon the recognition motif of ECMproteins and has been found to promote cell attachment [76]. This resulted in thespontaneous attachment of the peptide to the bare gold regions. Using this chemicalpattern, cell patterns of micron resolution were formed using BAEc and humanepidermal carcinoma cells. The use of normal mouse fibroblast (NIH3T3) cells,1-22