Light-controlled Assembly of Active Colloidal Molecules

TL;DR

This paper demonstrates a novel method to control active self-assembly of colloidal molecules using light, enabling dynamic behaviors like migration and rotation, which could advance the design of active materials.

Contribution

It introduces a new approach where activity emerges from light-controlled binding of immotile particles, unlike traditional methods focusing on individual particle properties.

Findings

Created active molecules with diverse behaviors such as migration, spinning, and rotation.

Controlled self-assembly dynamics via light-controllable nonreciprocal interactions.

Potential to inspire new active material designs and understanding of living matter.

Abstract

Thanks to a constant energy input, active matter can self-assemble into phases with complex architectures and functionalities such as living clusters that dynamically form, reshape and break-up, which are forbidden in equilibrium materials by the entropy maximization (or free energy minimization) principle. The challenge to control this active self-assembly has evoked widespread efforts typically hinging on engineering of the properties of individual motile constituents. Here, we provide a different route, where activity occurs as an emergent phenomenon only when individual building blocks bind together in a way that we control by laser light. Using experiments and simulations of two species of immotile microspheres, we exemplify this route by creating active molecules featuring a complex array of behaviors, becoming migrators, spinners and rotators. The possibility to control the dynamics of active self-assembly via light-controllable nonreciprocal interactions will inspire new approaches to understand living matter and to design active materials.