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This work reported a wireless controlled micro-actuator system for rapid heating and mixing of multiple droplets using integrated arrays of micro-fabricated 2.5 GHz solid-mounted thin-film piezoelectric resonators (SMRs) and a millimeter-scale omnidirectional antenna. An equivalent circuit is proposed to analyze the mechanism of the heating, mixing of the SMR and the wireless communication system. The heating and mixing rate can be tuned by adjusting the input power as well as the transmission distance between the transmitting antenna and the receiving antennas. A heating rate up to 3.7 °C per second and ultra-fast mixing of the droplet was demonstrated with the wireless microsystem. In addition, two types of circuits, H-shaped and rake-shaped, were designed and fabricated for parallel operating actuator array and controlling the power distribution with the array. Both uniform and gradient heating of the multiple droplets are achieved, which can be potentially applied for developing high-throughput wireless micro-reactor system.
On-chip integrating several functional components for developing integrated lab-on-a-chip microsystem remains as a challenge. In this work, by employing multiple microelectromechanical resonators both as actuators and sensors, on-chip heating, mixing and chemical reaction monitoring are successfully demonstrated. Mechanism studies using COMSOL simulations indicate that the local heating and mixing are induced by the acoustic wave attenuation during its transmission in liquid. On-line chemical reaction monitoring is realized by viscosity sensing using the same resonator through impedance analysis. Classic Diels-Alder reaction in a single droplet was performed to verify the feasibility of using such microsystem for mixing, heating and online reaction monitoring at microscale.