Soft materials for microfluidic sensing, actuation, and energy harvesting

Microfluidic and lab-on-a-chip technologies provide the abilities to perform laboratory operations on a small scale using miniaturized devices. Physical processes can be more easily controlled and harnessed when the dimensions of the instrument are reduced to the scales of micrometers. In addition to manipulate the liquids in the physical processes such as mixing, pumping, etc, we here demonstrate more potential invention for microfluidic systems which include biological sensing, remote actuation, and energy harvesting using soft materials.;In this work, one biological sensor is studied: we introduce a gycidyl derivatized dextran hydrogel. Dextran-glycidyl methacrylate (Dex-GMA) is synthesized as a hydrogel precursor by taking advantage of the functionality of the hydroxyl groups in dextran as well as the instability of the epoxy group in glycidyl methacrylate. Upon exposure to a sample solution that contains dextranase, the polymer chain is cleaved and the synthesized hydrogels incorporating Dex-GMA can dissolve in the sample solution. In this paper, we report a technique for photopatterning Dex-GMA hydrogel that is capable of enzymatic degradation.;Furthermore, we focuses on a new light-responsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel microacutators incorporating glycidyl methacrylate functionalized graphene oxide (GO-GMA) instead of metallic nanoparticle fillers. GO-GMA incorporated hydrogels are synthesized by photopolymerization of NIPAAm. Results show that such nanocomposite hydrogel can undergo large volumetric change in response to infrared (IR) light illumination, due to the highly efficient photothermal conversion of GO-GMA. It also exhibits significantly larger water uptake compared to conventional PNIPAAm hydrogel by 3 times. Based on the developed IR-responsive naonocomposite hydrogel, we have also realized a microvalve and microlens using this material that controls the fluidic flow within a microfluidic channel through remote IR light actuation.;Last, we demonstrate on a photoelectrochemical capacitor that can convert and store solar energy based on coupling between ferroelectricity and photoelectrochemical effect using ferroelectric polymer. We here demonstrate an interesting device of direct and simultaneous harvesting and storage of the solar energy in the electrical form in an intrinsically single structure. In addition, we also demonstrate quantum dots sensitized photoelectrochemical capacitor based on the same working mechanism.