Surface Modification of PDMS in Microfluidic Devices

Keywords Polydimethylsiloxane (PDMS), microfluidic devices, surface modification, physical adsorption, inner migration, high 

In recent years, this topic has been highlighted and reviewed elsewhere [1,4-6], However, it has been done in a fragmented way and only covers a few of the techniques used in practical operation. Hence, this chapter tries to review the 

AtulTiwari and Mark D. Soucek(eds.) Concise Encyclopedia of High Performance Silicones. (14i-i50) 2014 Scrivener Publishing LLC 

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Surface modification of PDMS has been used to retard swelling in organic solvents, which is particularly important for fabricating microfluidic devices and for some types of lithography. ... 

Since microfluidic devices are now widely used in various applications, particularly cell studies, low cell toxicity will be a big concern for surface modification techniques. Another issue for surface modification of PDMS is long-term stability, which is very important for commercialization of current microfluidic de-vices. This issue will significantly affect the shielding time and biology performance of the final PDMS-based microfluidic products. Solving this issue will accelerate the commercialization of microfluidic devices and benefit the whole microfluidic community and hence society. 

In 2004, Hisamoto and coworkers [19] have presented a simple approach, called capillary-assembled microchips (CAs-CHIP), for assembling a commercial square fused-silica capillaiy into a PDMS microfluidic device. The capUlaiy could be completely functionalized off-chip and cut into required size and then integrated raito a chip without any solution leakage (as shown in Fig. 3). As many methods for surface modification of capillary have been well established, the CAs-CHIP method offered a way to fabricate different microfluidic devices having various functions for analytical applications including sample pretreatment, biochemical sensors, and so on. 

Surface treatments and surface interactions are the challenges ahead for the research community in relation to the development of advanced, sophisticated microfluidic devices. Stuface modification techniques need to be optimized for various applications and particularly for disposable microfluidic devices. PDMS will be a popular material for future microfluidic devices, and some issues associated with most of the currently employed treatments, such as the hydrophobic recovery of PDMS surfaces, need to be adequately addressed. 

The solution-phase approach is cost effective and suitable for surface modification of microstructures of a complicated pattern. The method is designed for sealed PDMS-based microfluidic devices. It does not require their post-assembly and can be done repetitively in the same... 

Wong I, Ho CM (2009) Surface molecular property modifications for poly (dimethylsiloxane) (PDMS) based microfluidic devices. Microfluid Nanofluid 7(3) 291-306 Valente I, Celasco E, Marchisio DL, Barresi AA (2012) Nanoprecipitation in confined impinging jets mixers production, characterization and scale-up of pegylated nanospheres and nanocapsules for pharmaceutical use. Chem Eng Sci 77 217-227... 

As glass and quartz exhibit the same surface property as fused-silica capillary, the monolithic materials could be conveniently prepared in a glass- or quartz-based microfluidic device via the same way of monoliths in the capillary. However, glass/quartz devices are rather expensive, and the need for specialized facilities for their fabrication with conventional photolithography technology hinders any rapid modification of the chip architecture. An attractive alternative is using a variety of polymeric materials, such as poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), polycarbonate (PC), and cyclic olefin copolymer (COC), to fabricate microchips for their mechanical and chemical properties, low cost, ease of fabrication, and high flexibility. 

Morphology of features present on the surface is very important for the performance of microfluidic devices and can also play an important role in modification of their properties. Surface patterning by soft lithography is a very convenient technique for introducing controlled topography into PDMS surfaces ... 

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