A bacterial ratchet motor

TL;DR

This paper demonstrates that asymmetric micro-gears can spontaneously rotate in a bacterial bath due to self-assembled motile bacteria, revealing potential for harnessing active matter in micro-device propulsion.

Contribution

It introduces a novel method of inducing rotation in micro-gears using self-assembled bacteria, advancing the understanding of active matter for nanotechnology applications.

Findings

Asymmetric micro-gears rotate spontaneously in bacterial baths.

Self-assembly of bacteria along gear boundaries causes propulsion.

Active matter can surpass thermodynamic restrictions of passive fluids.

Abstract

Self-propelling bacteria are a dream of nano-technology. These unicellular organisms are not just capable of living and reproducing, but they can swim very efficiently, sense the environment and look for food, all packaged in a body measuring a few microns. Before such perfect machines could be artificially assembled, researchers are beginning to explore new ways to harness bacteria as propelling units for micro-devices. Proposed strategies require the careful task of aligning and binding bacterial cells on synthetic surfaces in order to have them work cooperatively. Here we show that asymmetric micro-gears can spontaneously rotate when immersed in an active bacterial bath. The propulsion mechanism is provided by the self assembly of motile Escherichia coli cells along the saw-toothed boundaries of a nano-fabricated rotor. Our results highlight the technological implications of active matter's ability to overcome the restrictions imposed by the second law of thermodynamics on equilibrium passive fluids.