Dynamic self-assembly of microscale rotors and swimmers

TL;DR

This paper demonstrates that active, immotile microscale components can self-assemble into structures exhibiting translation and rotation, mimicking biological motility, and can reversibly switch between these states.

Contribution

It introduces a method for designing active microscale components that self-assemble into motile structures with reversible transitions, advancing micromachine engineering.

Findings

Active metallic rods induce surface flows in chemical fuel.

Pairs of rods form swimmers or rotors, switching reversibly.

The system mimics bacterial run-and-tumble behavior.

Abstract

Biological systems often involve the self-assembly of basic components into complex and function- ing structures. Artificial systems that mimic such processes can provide a well-controlled setting to explore the principles involved and also synthesize useful micromachines. Our experiments show that immotile, but active, components self-assemble into two types of structure that exhibit the fundamental forms of motility: translation and rotation. Specifically, micron-scale metallic rods are designed to induce extensile surface flows in the presence of a chemical fuel; these rods interact with each other and pair up to form either a swimmer or a rotor. Such pairs can transition reversibly be- tween these two configurations, leading to kinetics reminiscent of bacterial run-and-tumble motion.