Low-power electrically controlled thermoelastic microvalves integrated in thermoplastic microfluidic devices

One of the major needs for the successful miniaturization of microfluidic systems is the integration of portable, low-voltage, low-power microvalves to manipulate the fluid flow through a network of microchannels. We report here a low-power, thermally actuated, elastomer-based microvalve with thermal isolation, which is then integrated in a thermoplastic microfluidic device. In the 6-layer design of each microvalve, the microfabricated heater that provides the thermal energy for the valve actuation is thermally isolated via an insulation cavity which reduces the heat dissipation to the surrounding. The 6-layer all-plastic microvalve was fabricated and showed a 40 % reduction in power consumption compared to the 4-layer design when the same duration was used for closing valves. A thermal model using COMSOL software was created to obtain further insight to the temperature profile in the microvalve region. The model was validated by comparing the simulated temperatures with experimentally measured values. The simulated values closely agreed with the measured temperatures. In addition, a two-step power application was created, which further reduced the power requirement. An initial power of 37 mW was used to close the valve in 11 s. After closure, a lower second-step power of 12 mW enabled the valve to remain closed for 15 min, which was only one-third of the initial power. By combining structural and operational improvement, the overall power consumption of the microvalve was reduced by 80 %. The 6-layer microvalve with two-step operation has the potential to realize a battery-operated microfluidic device for biological assays.