Force Characterization of Insect-Scale Aquatic Propulsion Based on Fluid-Structure Interaction

TL;DR

This paper presents the first systematic force characterization of insect-scale aquatic propulsors inspired by anguilliform swimming, using fluid-structure interaction and custom force sensors to measure thrust in microrobotic swimmers.

Contribution

It introduces a theoretical framework and experimental data for force measurement of novel insect-scale propulsors driven by shape-memory alloy actuators.

Findings

Maximum thrust of 0.61 mN for dual-tail propulsor

Cycle-averaged force of 22.6 micro-N for dual-tail design

First measurements of instantaneous thrust for this type of microrobotic propulsors

Abstract

We present force characterizations of two newly developed insect-scale propulsors--one single-tailed and one double-tailed--for microrobotic swimmers that leverage fluid-structure interaction (FSI) to generate thrust. The designs of these two devices were inspired by anguilliform swimming and are driven by soft tails excited by high-work-density (HWD) actuators powered by shape-memory alloy (SMA) wires. While these propulsors have been demonstrated to be suitable for microrobotic aquatic locomotion and controllable with simple architectures for trajectory tracking in the two-dimensional (2D) space, the characteristics and magnitudes of the associated forces have not been studied systematically. In the research presented here, we adopted a theoretical framework based on the notion of reactive forces and obtained experimental data for characterization using a custom-built micro-N-resolution force sensor. We measured maximum and cycle-averaged force values with multi-test means of respectively 0.45 mN and 2.97 micro-N, for the tested single-tail propulsor. For the dual-tail propulsor, we measured maximum and cycle-averaged force values with multi-test means of 0.61 mN and 22.6 micro-N, respectively. These results represent the first measurements of the instantaneous thrust generated by insect-scale propulsors of this type and provide insights into FSI for efficient microrobotic propulsion.