Over the last ten years, microfluidic technologies have gained considerable importance. However, realising highly integrated microsystems is a major challenge, which so far has only been solved insufficiently. Here, we present an innovative approach to fabricate low-cost, integrable mi- crofluidic platforms. As active elements, photopolymerised hydrogels based on Poly(N-isopropylacrylamide) (PNIPAAm) are introduced. PNIPAAm is temperature-sensitive. Heated in water above its lower crit- ical solution temperature (LCST), it reversibly changes from a swollen to a shrunken state (volume change in the order of 90%) and can, via an electrothermic interface, be employed as electrothermally switchable actuator. Varying specific parameters in the swelling agent, for example varying its alco- hol concentration, can shift the LCST. So not only micropumps or microvalves, but also valves with an appointed threshold value, so-called chemostats or chemical transistors, can be realised. Using the example of a microchip performing enzymatic endpoint analyses, we investigate characteristic be- haviour of active elements based on PNIPAAM and show the ability of integrating different fluidic operations like fluid transportation, metering, valving and mixing into one fully polymeric microchip.
Preparation of Organic Light-Emitting Diode Using Coal Tar Pitch, a Low-Cost Material, for Printable Devices