(158e) Smart Nanogel-Containing Membranes in Microchip for Temperature- and Ethanol-Responsive Permeability Regulation

Authors: 
Wang, W., Daqing Oilfield Company Ltd., PetroChina
Chu, L. Y., Sichuan University
Xie, R., Sichuan University
Ju, X. J., Sichuan University
Liu, Z., Sichuan University
Recently, integration of membranes in microchips has shown great potential for biomedical fields such as analysis, separation, microreaction and cell-based study, due to their portability and lower consumption of sample and energy. In particular, microchips containing smart membranes that can change their permeability in response to external chemical/physical stimuli are important and necessary, as they can be used as sensors, separators and controlled release systems. Here we report on novel types of smart in-chip membranes containing stimuli-responsive nanogels as nanovalves for self-regulation of permeability. Such smart in-chip membranes can be integrated into microchips by assembly of a pre-fabricated nanogel-containing membrane into microchannels, or in situ fabrication of a nanogel-containing membrane in the microchannel. To demonstrate the first strategy for fabricating smart in-chip membranes, a polyethersulfone membrane, prepared by blending poly(N-isopropylacrylamide) (PNIPAM) nanogels into the membrane-forming solution via vapor-induced phase separation process, is sandwiched between two polydimethylsiloxane modules of a microchip. To demonstrate the second strategy, a chitosan membrane containing PNIPAM nanogels, is in situ fabricated in microchannels, based on crosslinking reaction at the interface between two parallel laminar flows. The PNIPAM nanogels, that allow temperature-responsive and ethanol-responsive swelling/shrinking volume transitions, serve as smart nanovalves for controlling the diffusional permeability of solutes across the membrane. Based on this, both membranes can show excellent temperature- and ethanol-dependent permeability, rapid responsive rate, and good repeatability and stability. These studies provide promising strategies for creation of versatile nanogel-containing smart membranes within microchips via simply changing the functional nanogels for developing micro-scale detectors, sensors, separators and controlled release systems.
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