Thermoplastic elastomer gels: an advanced substrate for microfluidic chemical analysis systems.
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We demonstrate the use of thermoplastic elastomer gels as advanced substrates for construction of complex microfluidic networks suitable for use in miniaturized chemical analysis systems. These gels are synthesized by combining inexpensive polystyrene-(polyethylene/polybutylene)-polystyrene triblock copolymers with a hydrocarbon extender oil for which the ethylene/butylene midblocks are selectively miscible. The insoluble styrene end blocks phase separate into localized nanodomains, resulting in the formation of an optically transparent, viscoelastic, and biocompatible gel network that is melt-processable at temperatures in the vicinity of 100 degrees C. This unique combination of properties allows microfluidic channels to be fabricated in a matter of minutes by simply making impressions of the negative relief structures on heated master molds. Melt processability allows multiple impressions to be made against different masters to construct complex geometries incorporating multi-height features within the same microchannel. Intricate interconnected multilayered structures are also easily fabricated owing to the ability to bond and seal multiple layers by briefly heating the material at the bond interface. Thermal and mechanical properties are tunable over a wide range through proper selection of gel composition.