Computational and experimental design of fast and versatile magnetic soft robotic low Re swimmers

TL;DR

This paper presents a comprehensive design and analysis of magnetic soft robotic swimmers at micro scales, optimizing their kinematic performance for biomedical applications through computational and experimental methods.

Contribution

It introduces a fully coupled fluid-structure interaction model for designing and comparing two biomimetic low Re swimming modes, advancing the understanding of their performance and stability.

Findings

Helical swimmer is the fastest in body lengths per cycle.

Undulatory swimmer is the most versatile and stable.

Design strategy enables optimized performance at micro scales.

Abstract

Miniaturized magnetic soft robots have shown extraordinary capabilities of contactless manipulation, complex path maneuvering, precise localization, and quick actuation, which have equipped them to cater to challenging biomedical applications such as targeted drug delivery, internal wound healing, and laparoscopic surgery. However, despite their successful fabrication by several different research groups, a thorough design strategy encompassing the optimized kinematic performance of the three fundamental biomimetic swimming modes at miniaturized length scales has not been reported till now. Here, we resolve this by designing magnetic soft robotic swimmers (MSRSs) from the class of helical and undulatory low Reynolds number (Re) swimmers using a fully coupled, experimentally calibrated computational fluid dynamics model. We study (and compare) their swimming performance, and report their steady-state swimming speed for different non-dimensional numbers that capture the competition by magnetic loading, non-linear elastic deformation and viscous solid-fluid coupling. We investigate their stability for different initial spatial orientations to ensure robustness during real-life applications. Our results show that the helical 'finger-shaped' swimmer is, by far, the fastest low Re swimmer in terms of body lengths per cycle, but that the undulatory 'carangiform' swimmer proved to be the most versatile, bi-directional swimmer with maximum stability.