An Autonomous Subgram SMA-Based Swimmer

2026-06-12

AI Summary

This work addresses the challenge of achieving autonomous propulsion and navigation in sub-gram-scale underwater robots without external power or control. The authors present Swima, a 900-mg untethered microrobot that integrates, for the first time, an onboard lithium-ion battery (507 mg), a custom-printed circuit board, two 10-mg high-power-density shape memory alloy actuators, and an autonomous trajectory-tracking control algorithm, enabling fully self-contained propulsion, power supply, and computation. Experimental results demonstrate that Swima can swim autonomously for over 18 minutes at a maximum speed of 22.4 mm/s (0.56 body lengths per second), achieve a peak turning rate of 14°/s, and maintain a heading tracking error with a root-mean-square value of 6.5°. To the best of the authors’ knowledge, Swima is the first sub-gram autonomous swimming microrobot with full onboard capabilities.

Abstract

We present the Swima, a bioinspired 900-mg swimmer propelled by two 10-mg high-work-density (HWD) actuators driven by shape-memory alloy (SMA) wires. We integrated onboard power and computation by using a custom-built printed circuit board (PCB) and an 11-mAh 3.7-V 507-mg single-cell lithium-ion (Li-Ion) battery, which in conjunction enable autonomous swimming in excess of 18 min. The Swima can swim at speeds of up to 22.4 mm/s (0.56 Bl/s), achieves turning rates of up to 14°/s, and can follow 0-degree heading reference trajectories with root mean square (RMS) values of tracking errors of about 6.5° across multiple tests. This robot is the first subgram microswimmer with onboard power, actuation, and computation developed to date.

Problem

• microswimmer
• autonomous
• subgram
• onboard power
• shape-memory alloy

Innovation

• subgram microswimmer
• shape-memory alloy (SMA) actuator
• onboard autonomy
• bioinspired robotics
• high-work-density actuation