PDMS Surface Patterning

Chitosan-stabilized Au NPs can be selectively synthesized on surfaces like poly (dimethylsiloxane) (PDMS) films using HAuC14 as precursor. The computation of surface plasmon bands (SPBs) based on Mie theory and experimental results indicates that the particles are partially coated by chitosan. The proposed mechanism implies that chitosan acts as a reducing/stabilizing agent. Furthermore, PDMS films patterned with chitosan could induce localized synthesis of gold nanoparticles in regions capped with chitosan only [110]. 

Polysiloxanes are apparently the materials of choice in the new soft-lithography techniques.376 380 The method is outlined briefly in Figure 4.20. In the first step, linear (liquid) PDMS is poured over the surface of the master to be reproduced. It is then cross linked, and peeled away from the master surface. The PDMS surface containing the pattern is then coated with a hydrophobic alkane thiol, and the pattern transferred to a... 

Chick embryo heart muscle cells were patterned and grown on a fibronectin (FN) surface patterned by PDMS stamping. The PBS solution (containing Ca2+ and K+) was used to stimulate spontaneous muscle contraction [198]. Laminar flows provide a reaction path (buffer plus 1-octanol) and a control patch (buffer only) for study of communication between excitable cells (cardiomyocytes) through gap junctions (see Figure 8.18) [198]. 

Fig. 17 Micropattemed surfaces allow ultrahigh-throughput production of size-specified aggregates. Surfaces patterned were generated in (a) poly(dimethylsiloxane) (PDMS) with wells of (b) 100, 200, 400 and 800 pM. (c) Sections of PDMS textured with 400 pM wells were inserted into wells in a 24-well plate. A single-cell suspension of hESCs was dispensed into the microwells. After 24 h, the well contents were imaged, extracted and re-imaged, (d) Aggregates were formed only in the presence of 10 pM of the ROCK inhibitor Y-27632, in the presence or absence of centrifugation. Scale bars 400 pM [134]...

Focus on the PDMS surface next to the marked spot. Write gradients/ patterns (Fig. 4B). 

Fig. 8.9 SEM and AIM images of surface patterns when compressing an oxidized PDMS film either (a) sequentially or (b) simultaneously [22]...

The obtained patterned polymer surfaces can also be replicated by metal thermal evaporation to produce nanostructured metallic films with holes or asperities of controlled size, as illustrated in Fig. 11.10. After deposition of a sufficiently thick metal layer, the polymer layer can be cleaved or dissolved away. This procedure allows an efficient and precise control of the metallic surface structure, with possible applications in materials science and photonics. The roughness of polydimethylsiloxane (PDMS) surfaces can be tuned by this technique if the PDMS is treated while cross-linking, which may be of interest for microfluidic applications. We have also observed that substrates of poly(methyl methacrylate) (PMMA), PS in the form of colloidal spheres and bulk, and semiciystalline films of polyethylene (PE) are prrMie to be structured by this technique, evidencing the versatility and potential for its widespread use. It may find applications in many different scientific and technological fields like nanoUthography, microfluidics, or flexible electronics. 

Immunoassay Microfluidic networks have high resolution and contrast capabilities for simultaneously patterning lines of proteins onto a surface. This has been utilized, for example, by Bernard et al. [13], to create a miniaturized mosaic of inununoassays by patterning lines of antigens on PDMS surfaces by a microfluidic network and delivering the analytes by another set of microfluidic channels at right angles to the direction of the first set. Microfluidic separations have also been combined with... 

Biologically active molecules are sometimes trapped in PDMS when end-functionalized PDMS chains are linked into a network structure. This method has been done, for example, with a lipase enzyme. The PDMS plays a beneficial role as an activator or protective agent. Similar results were found for the enzyme a-chymotripsin, with some short-chain poly(ethylene oxide) used to enhance enzymatic activity. It is also possible to generate microtopographic patterns that affect Escherichia coU biofilm formation on PDMS surfaces. 

Another study focused on PDMS surfaces made hydrophilic by modification with hydrophobins (small, cysteine-rich and amphiphilic fungal proteins). This approach was used to pattern antigen molecules, followed by immunoassays. For example, chicken immunoglobulin G was found to be compatible with the hydrophhobin-modified PDMS. 

The limited use of macromolecular inks can be attributed to poor wetting characteristics of PDMS surfaces by many polymers. A variety of approaches exist for patterning macromolecules on substrates using microcontact printing methods. 

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