Surface acoustic wave propulsion system with acoustic radiation force

Abstract

This study is based on the conventional dimension of U-IDT actuator to discuss the feasibility of swimmer propulsion system with surface acoustic wave (SAW). Acoustic radiation force with SAW has been widely used in the field of microfluidics. Acoustic radiation propulsion (ARP), a reaction force of acoustic radiation force (ARF), has rarely been discussed. This reaction phenomenon may actually play a significant role in the swimmer propulsion system. To investigate this phenomenon, a prototype swimmer is designed in this study. The swimmer converts ARP with SAW into movement and force in water. Rayleigh Wave is excited with a 128° Y-rotated X-propagation lithium niobate U-IDT actuator. The evidence of movement and propulsion are confirmed in water by the no load speed and zero speed propulsion measurements. ARP, based on acoustic impedance difference, can shift the gravity center of prototype swimmer every time. At 9.61 MHz, 100 mm/s no load speed and 4 mN zero speed propulsion are measured in water, when driving voltage is around 75 V0p. ARF with U-IDT actuator is estimated by the time average. The comparison between the calculation and measurement results had a similar response. In future, miniaturization and low voltage of ultrasonic actuator can be achieved with higher frequencies. Simultaneously, high power density will be maintained because the vibration velocity is not varied extremely. Moreover, wave vibration with ARP may maintain blood activation to reduce the possibility of thrombosis during and after surgery. Thus, the micro swimmer propulsion system with SAW deserves to be expected in blood vessels, based on the advantages of high power density, self-propelled and simple structure.