Abstract
The development of magnetically powered microswimmers that mimic the swimming mechanisms of microorganisms is important for lab‐on‐a‐chip devices, robotics, and next‐generation minimally invasive surgical interventions. Governed by their design, most previously described untethered swimmers can be maneuvered only by varying the direction of applied rotational magnetic fields. This constraint makes even state‐of‐the‐art swimmers incapable of reversing their direction of motion without a prior change in the direction of field rotation, which limits their autonomy and ability to adapt to their environments. Also, due to constant magnetization profiles, swarms of magnetic swimmers respond in the same manner, which limits multiagent control only to parallel formations. Herein, a new class of microswimmers are presented which are capable of reversing their direction of swimming without requiring a reversal in direction of field rotation. These swimmers exploit heterogeneity in their design and composition to exhibit reversible bidirectional motion determined by the field precession angle. Thus, the precession angle is used as an independent control input for bidirectional swimming. Design variability is explored in the systematic study of two swimmer designs with different constructions. Two different precession angles are observed for motion reversal, which is exploited to demonstrate independent control of the two swimmer designs.
Highlights
There exist motile microorganisms such as bacteria and sperm cells that adopt versatile swimming mechanisms to improve their mechanical efficiency regardless of the rheological characteristics of their environment
We demonstrate two swimmer designs with different head-flagellum tilt but same material composition result in two different precession angles for motion reversal
We describe an asymmetric microswimmer with a rigid triangular head attached to a long flexible flagellum, with a tilt angle between the two components
Summary
There exist motile microorganisms such as bacteria and sperm cells that adopt versatile swimming mechanisms to improve their mechanical efficiency regardless of the rheological characteristics of their environment. Advances in microfabrication have enabled the construction of micro-swimmers which can reconfigure their morphology in order to achieve locomotion in confined workspaces.[1920] Many of these previously developed micro-swimmers lack the ability to actively reverse their magnetic anisotropy while in motion. These swimmers cannot readily reverse their swimming direction like bacteria or sperm cells, without a prior simultaneous reversal in the direction of the applied magnetic field. Our findings contribute to the state-of-the-art fabrication methods premised upon photolithography by achieving functionally dissimilar swimmers with batch fabrication
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