Fabrication, Propulsion, and Assembly of Shape-Morphing Colloidal Particles under Orthogonally Applied Electric Fields

Over the past decade, numerous studies have explored the use of external fields to remotely control the motion of active particles. However, most of these efforts have focused on particles with static morphologies, which inherently limit their ability to achieve programmable motion.

In this work, we present the fabrication, propulsion, and assembly of shape-morphing colloidal particles under orthogonally applied AC electric fields. These particles (40 x 4 um and 800 nm thick) are composed of a thermoresponsive hydrogel layer, which swells or deswells in response to temperature changes, and a glassy polymer layer that mechanically constrains the deformation. Upon cooling, the hydrogel layer swells while the glassy layer remains rigid, transforming the particles from flat rectangular prisms at 45C to crescent-shaped prisms at 5C. The geometric and compositional asymmetries of particles enable electrohydrodynamic interactions that drive directed propulsion (~5-20 um/s) under electric fields (0.5 × 10⁵ to 5 × 10⁵ Vpp/m, 0.8-2 kHz). Furthermore, this propulsion behavior promotes the assembly of particles into various types of clusters, such as double-crescent rotators, windmills, whose dynamics can be further tuned by temperature-induced shape transformations.