PDMS Surface Modification

PDMS in its native form does not possess reactive groups that can be used for the covalent attachment of NAs [51]. However, the PDMS surface can be plasma induced oxidized and then fimctionaUzed with organosilanes carrying the desired head group. For example, a PDMS surface has been modified with 3-mercaptotrimethoxysilane to yield a thiol-terminated surface, to which a 5 -acrylamide modified DNA has been covalently attached [52]. See Fig. 13 for a representation of the PDMS surface-modification process. 

One successful method for PDMS surface modification is ultraviolet polymer grafting. In this method. 

Zhou, J., Ellis, A. V, Voelcker, N. H. (2010). Recent developments in PDMS surface modification for microfluidic devices. Electrophoresis, 31, 2-16. 

This approach was borrowed from the conventional bulk modification of thermal plastics, by bulky blending a few amounts of other molecules (additives) into the plastic matrix to modify some performance of plastics [7]. For example, to increase the flowability of melt thermal plastics in hot embossing or injection, plasticizers such as dibutyl phtha-late are often added in the thermal plastics. Some of them will appear on the surface and further change the properties of the target surface (Figure 10.2a). This approach can be directly transferred to PDMS surface modification as well [8]. 

Figure 10.1 Classification of PDMS surface modification approaches.

Figure 10.2 Samples of PDMS bulk modification (A, blending) and PDMS surface modification (B, dynamic coating).

Figure 10.3 PDMS surface modification with various physical...

Figure 10.4 PDMS surface modification through inner...

Figure 10.6 Scheme of PDMS surface modification through high energy etqjosure. 

Chemical vapor deposition (CVD) is a chemical process used to produce high-purity and high-performance soUd materials. In a typical CVD process, the wafer (substrate) is exposed to one or more volatile precursors, which react or decompose on the substrate surface to produce the desired deposit. The CVD method is widely used in microfabrication processes to deposit materials in various forms through polymerization of functionalized [2.2] paracyclophanes. The CVD method is also used to make reactive coatings for PDMS. Figure 10.7 shows one of these processes used for PDMS surface modification. 

Figure 10.8 A typical process of sol-gel processing for PDMS surface modification.

Figure 10.9 Scheme of a typical process of silane chemistry for PDMS surface modification. 

Table 10.2 The comparison of various approaches of PDMS surface modification.

Figure 23.13 Water contact angles on a PDMS surface modifed with PEG6, when left in air at room temperattue, measured over time. Reproduced with permission from [54] Copyright 2009 Soft Matter.

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