Flow Control Using a Thermally Actuated Microfluidic Relay Valve

This paper demonstrates a new two-stage valving concept for microfluidic systems that uses the reversible gelation of a thermally responsive polymer solution in a control channel to deflect a membrane into the main flow channel for flow control. This method can control flow through a system of microchannels using integrated electric heating elements and only one control pressure source, compared to the off-chip pressure manifold needed in existing systems. This valve technology therefore enables portable microfluidics-based diagnostic tools for biomedical applications and environmental monitoring allowing on-site analysis. Valves with zero leakage rates and a response time of about 3 s have been achieved.