Acoustic Propulsion in Liquid and Air

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This research explores acoustic propulsion of microrobots in liquid and air, to navigate to destinations without mechanical engine or propeller and driven only with electrical signal and power. This research is based on the preliminary work that in liquid, acoustic streaming effect makes liquid jet be shot out from a focused ultrasonic transducer, causing the transducer to move in liquid. In air, synthetic air jet through an orifice has been shown to move the transducer in the opposite direction of the jet flow. Here the fundamental principles and underlying mechanisms in acoustic propulsion in liquid and air will be studied. Various microelectromechanical systems (MEMS) based propellers with high efficiency and directionality will be explored. The novelty of the proposed research of acoustic propulsion in air and liquid is that it does not require moving parts, heat, audible sound, or combustion of fuel, and is very friendly to environment. The successful outcome of the research will result in a subminiature electric propulsion unit (including the drive electronics), that can produce thrust ratios of 10:1 and 40:1 in air and liquid, respectively. Thus, the research will greatly impact propulsion technology for microrobots and implantable devices. The research will also produce new insights on how to produce powerful ultrasound with MEMS piezoelectric transducers and sub-miniature electronics over a wide frequency range from 40 kHz to 900 MHz. Students from underrepresented groups will actively be recruited and given opportunities to be involved in the proposed research. The high school students will participate in the design and experimentation of acoustic propellers. The research is to explore various MEMS based acoustic transducers for ultrasound generation in air and liquid over a wide frequency range (40 - 500 kHz in air and 0.5 – 900 MHz in liquid). As the transducers are designed and microfabricated, the transducers’ acoustic intensities and their field patterns will be simulated and measured. To ensure large sound outputs and controlled propulsion directionality, the transducers will be operated at their resonant frequencies, and novel focusing techniques will be explored and developed. The ultimate goal of the proposed research is to develop MEMS-based, wireless and battery-powered acoustic propulsion systems for microrobots in liquid and air. Various microfabrication technologies for the processing of the transducers and associated components will be explored. Prototype units with the transducers and electronics will be developed, and fundamental limits on thrust force per unit weight (or volume) of the propulsion system and precision control of the thrust direction will be studied.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.