PDMS Surface Modification for Application on Thermally-Responsive Hydrogel Microvalves

Recent developments in (MEMS) fabrication techniques have exploited the properties of polymers. Traditional lithographic techniques have been used to create a template in a thick layer of photoresist that can be filled with a heat -0r-UV curable polymer and used to cast numerous replicas of Tesla channels in an elastomeric material-poly (dimethylsioloxane) (PDMS). The surface of this replica, and that of a flat slab of PDMS, is oxidized in oxygen plasma and brought into conformal contact to seal tightly. N-isopropylacrylamide polymers have attracted much interest in the area of scientific research and microfluidic technologies due to their unique thermal response in aqueous medium. To design microactuators of these gels with a high aspect ratio and a strong adhesion to the microchannel, substrates have to be developed. To achieve this, a modification of the simple (NIPA) polymer is needed; therefore, this calls for chemical modification of the (NIPA) material itself and the PDMS. The integration of autonomous microvalves into complex microfluidic Tesla channel networks is presented. Hydrogel directly grown onto vinyl modified PDMS and is in contact with process medium. Thermoelectric element capable of changing the temperature of the system is used to actuate the valve. A distortable diaphragm at the center coupled to a piezoelectric that is connected to the ports of two channels. The other ends are connected to two small water tanks. Valve operation results in an oscillating or a positive net flow depending on valve status.