# Low-Voltage High-Frequency Lamb-Wave-Driven Micromotors

## TL;DR

This paper introduces a new micromotor driven by Lamb waves, which requires low voltage and is suitable for microfluidic applications like lab-on-a-chip systems.

## Contribution

The first Lamb-wave-driven micromotor is proposed, offering lower voltage and smaller size compared to traditional surface acoustic-wave-driven motors.

## Key findings

- The micromotor achieves 250 rpm with a 5 mm rotor and 6 V input voltage.
- Lamb waves generate strong acoustic streaming effects over a short distance.
- Design features like reflectors and acoustic openings reduce wave energy leakage.

## Abstract

By leveraging the benefits of a high energy density, miniaturization and integration, acoustic-wave-driven micromotors have recently emerged as powerful tools for microfluidic actuation. In this study, a Lamb-wave-driven micromotor is proposed for the first time. This motor consists of a ring-shaped Lamb wave actuator array with a rotor and a fluid coupling layer in between. On a driving mechanism level, high-frequency Lamb waves of 380 MHz generate strong acoustic streaming effects over an extremely short distance; on a mechanical design level, each Lamb wave actuator incorporates a reflector on one side of the actuator, while an acoustic opening is incorporated on the other side to limit wave energy leakage; and on electrical design level, the electrodes placed on the two sides of the film enhance the capacitance in the vertical direction, which facilitates impedance matching within a smaller area. As a result, the Lamb-wave-driven solution features a much lower driving voltage and a smaller size compared with conventional surface acoustic-wave-driven solutions. For an improved motor performance, actuator array configurations, rotor sizes, and liquid coupling layer thicknesses are examined via simulations and experiments. The results show the micromotor with a rotor with a diameter of 5 mm can achieve a maximum angular velocity of 250 rpm with an input voltage of 6 V. The proposed micromotor is a new prototype for acoustic-wave-driven actuators and demonstrates potential for lab-on-a-chip applications.