Multiple actuation microvalves in wax microfluidics
Microvalves are an essential component of microfluidic devices. In this work, a low-consumption (<35 mJ), fast-response (<0.3 s), small footprint (<0.5 mm(2)) wax microvalve capable of multiple actuation is described. This phase-change microvalve is electrically controlled, simple to operate and can be easily fabricated as a fully integrated element of wax microfluidic devices through a special decal-transfer microlithographic process. The valve is inherently latched and leak-proof to at least 100 kPa. A minimum pressure of 3 kPa is required for valve opening. Maximum pressures for a successful closing in air and liquid are 90 and 40 kPa, respectively. The wax valve exhibits reversible open-close behaviour without failure for up to 10 actuation cycles in air (60 kPa) and 5 in water (30 kPa). To the best of our knowledge, this microvalve has the lowest energy consumption (two orders of magnitude lower) reported so far for a plug-type phase-change valve. Furthermore, its size, actuation mechanism and fabrication technology make it suitable for large-scale integration in microfluidic devices. Detailed characteristics in fabrication and actuation of the wax microfluidic valve as well as a test example of its performance for liquid dispensing are reported.