On-chip microfabrication of thermally controllable PNIPAAm microvalves by using optical maskless stereolithography

A growing trend of lab-on-a-chip (LOC) technologies is to achieve large-scale integration of components and functionalities. In this paper, we present an optical in-situ microfabrication technology, i.e. optical maskless stereolithography, for on-chip component fabrication and integration. It is demonstrated that poly(N-isopropylacrylamide) (PNIPAAm) can be rapidly patterned into high-resolution 2D/3D microstructures and in-channel PNIPAAm microvalves can be adaptively fabricated on a microfluidic chip by using the UV light based optical maskless exposure technology. The PNIPAAm microvalve can be repeatedly switched off and on by tuning its temperature between 20 and 37 °C, respectively. Such an in-situ microfabrication approach is promising in the development of multifunctional microfluidic chips integrated with micro-sensors and actuators.