Rational design and fabrication of versatile active colloidal molecules

TL;DR

This paper introduces a versatile fabrication method for creating customizable active colloidal molecules with programmable shapes, compositions, and motion modes, enabling advanced studies and applications in active matter and micro-robotics.

Contribution

The authors develop a sequential capillarity-assisted particle assembly technique to produce active colloids with tailored geometries and functionalities, overcoming previous limitations in programmability.

Findings

Created colloidal molecules that can translate, circulate, and rotate autonomously.

Engineered colloids that switch motion modes under external stimuli.

Demonstrated potential for customized active matter systems.

Abstract

Active colloids, also known as artificial microswimmers, are self-propelled micro and nanoparticles that convert uniform sources of fuel (e.g. chemical) or uniform external driving fields (e.g. magnetic or electric) into directed motion by virtue of asymmetry in their shape or composition. These materials are currently attracting enormous scientific attention for two main end uses. First, active colloids are prototypical internally driven, out-of-equilibrium systems and their study has led to new emergent material properties, such as swarming and living crystallization. Secondly, they hold the promise to be used as micro- and nanoscale devices with tremendous potential from medical to environmental applications. However, the current fabrication of active colloids is limited in the programmability of materials, geometry, and modes of motion. Here, we use sequential capillarity- assisted particle assembly (sCAPA) to link microspheres of different materials into clusters of prescribed shapes ("colloidal molecules") that can actively translate, circulate and rotate powered by asymmetric electro-hydrodynamic flows. Further engineering of the geometry and composition provides active colloids that switch motion under external triggers or perform simple pick-up and transport tasks. Our fabrication strategy enables both physicists and engineers to design and create customized active colloids to explore novel fundamental phenomena in active matter and to investigate materials and propulsion schemes that are compatible with future applications.