Surface-Acoustic-Wave-Driven Directional Atomizers Integrated With Pico-Liter Micropumps

In this paper, a surface-acoustic-wave (SAW)-driven atomizer with micropumps was developed. The micropumps consisted of an epoxy-based reservoir with an exhaust slot and a pair of interdigital transducers (IDTs). The liquid supply from the reservoir was controlled by SAW bursts from the IDTs. A microsurge tank was fabricated into the exhaust slot to stabilize the atomization. The transferred liquid was atomized by a pair of arc-shaped IDTs (AS-IDTs). The AS-IDT was optimally designed using optical vibration observations to focus the SAW energy into a single point and enabled high directional atomization. In the operational test of the micropump with water, a transfer rate of 0.24 pl per single burst was confirmed, where the burst signal is operated at 24.1 MHz with a 50% duty cycle, 40-ms period, and 70 Vp_p amplitude. In the water atomization test, we succeeded in ejecting a narrow mist spray from the substrate using a burst signal operating at 23.8 MHz with a 20% duty cycle, 1-ms period, and 50 Vp_p amplitude. The width of the ejected mist spray was 0.7 mm in the vicinity of the substrate, and was maintained at <;1 mm within the ejection height of 8 mm.