Magnetic manipulation of self-assembled colloidal asters

Abstract

A suspension of magnetic colloidal particles confined at a liquid–liquid interface and energized by an external periodic magnetic field self-assembles into star-shaped structures that can be magnetically manipulated to capture and transport smaller non-magnetic particles. Self-assembled materials1,2,3,4 must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity1,5. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots.