Self-regulated flow control in microchannels by the modification of walls with stimuli-responsive polymer

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In this decade, micro-analytical systems composing of fabricated micro-channels on chips has extremely investigated and applied to the wide areas. In the present study, a novel methodology for the fluid control complicate micro-channels was developed. The stimuli-responsive polymer that changes its hydrophilic-hydrophobic properties by stimuli was used to modify the wall of channels. The modification was successfully achieved by binding silane coupling agent on glass walls and the subsequent aqueous radical co-polymerization of N-isopropylacrylamide and a certain monomer having functional group that can bind to the objective compound. I could successfully control the surface wettability by stimuli such as temperature, salt, or surfactants. The wettability change results in the on-off of the stream or switching the flow direction. The contrast of the wettability was significantly improved by the modification with highly hydrophobic octadecylsilane accompanying with stimuli-responsive polymer. Furthermore, the modification onto the surfaces having sub-micro meter order of asperity was quite effective for obtaining-both of highly wettable and waters repellent surfaces. The polymer containing carboxyl or imidazole moieties can varied the hydrophilic-hydrophobic properties depending on the acid-alkaline conditions. The polymer including phenylborate substituents that can bind to sugar could not respond against glucose. On the other hand, the hydrophobicity of the polymer having the both of phenylborate and dimethylamino groups increased by the presence of glucose. The modification by such stimuli-responsive polymer will be effective for making glucose-responsive flow control system.