A bubble-powered micro-rotor: conception, manufacturing, assembly, and characterization

TL;DR

This paper presents a novel micro-rotor powered by microstreaming around ultrasound-excited microbubbles, demonstrating its fabrication, assembly, and characterization, with potential for MEMS-based micro-motors.

Contribution

It introduces a new micro-rotor actuation method using microstreaming, including its design, manufacturing, and experimental analysis of performance factors.

Findings

Rotational speeds up to 625 rpm achieved.

Power output estimated in the femtowatt range.

Rotor stability influenced by bubble size and acoustic parameters.

Abstract

A steady fluid flow, called microstreaming, can be generated in the vicinity of a micro-bubble excited by ultrasound. In this article, we use this phenomenon to assemble and power a microfabricated rotor at rotation speeds as high as 625 rpm. The extractible power is estimated to be on the order of a few femtowatts. A first series of experiments with uncontrolled rotor shapes is presented, demonstrating the possibility of this novel actuation scheme. A second series of experiments with 65 micron rotors micromanufactured in SU-8 resin are presented. Variables controlling the rotation speed and rotor stability are investigated, such as the bubble diameter, the acoustic excitation frequency and amplitude, and the rotor geometry. Finally, an outlook is provided on developing this micro-rotor into a MEMS-based motor capable of delivering tunable, infinitesimal rotary power at the microscale.