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

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.