Targeted Assembly and Synchronization of Self-Spinning Microgears

TL;DR

This paper demonstrates how non-equilibrium, energy-consuming active particles can be used to self-assemble dynamic, synchronized microgears with programmable behavior, advancing the design of autonomous micro-machines.

Contribution

It introduces a method to create self-spinning microgears and superstructures using photoactive, fuel-consuming particles that harness non-equilibrium phoretic phenomena for controlled self-assembly.

Findings

Formation of self-powered rotors and superstructures from active particles.

Use of light patterns to control self-spinning microgears.

Quantitative modeling of chemical gradient interactions.

Abstract

Self-assembly is the autonomous organization of components into patterns or structures: an essential ingredient of biology and a desired route to complex organization. At equilibrium, the structure is encoded through specific interactions, at an unfavorable entropic cost for the system. An alternative approach, widely used by Nature, uses energy input to bypass the entropy bottleneck and develop features otherwise impossible at equilibrium. Dissipative building blocks that inject energy locally were made available by recent advance in colloidal science but have not been used to control self-assembly. Here we show the robust formation of self-powered rotors and dynamical superstructures from active particles and harness non-equilibrium phoretic phenomena to tailor interactions and direct self-assembly. We use a photoactive component that consumes fuel, hematite, to devise phototactic microswimmers that form self-spinning microgears following spatiotemporal light patterns. The gears are coupled via their chemical clouds and constitute the elementary bricks of synchronized superstructures, which autonomously regulate their dynamics. The results are quantitatively rationalized on the basis of a stochastic description of diffusio-phoretic oscillators dynamically coupled by chemical gradients to form directional interactions. Our findings demonstrate that non-equilibrium phenomena can be harnessed to shape interactions and program hierarchical constructions. It lays the groundwork for the self-assembly of dynamical architectures and synchronized micro-machinery.