Reconfigurable Transport and Assembly of Colloidal Particles via Opto-Chemical-Electronic Tweezer (OCET)

Transporting and assembling colloidal particles is key to applications such as drug delivery, the fabrication of functional materials, and microrobotics. As a result, there is intense effort in developing techniques for manipulating colloids at high spatial and temporal resolutions, and in a dynamic, reconfigurable manner. Although optical manipulation provides precise particle control, its application is often limited by high energy requirements and intricate setups. In this study, we present an opto-chemical-electronic tweezer (OCET), a novel particle manipulation strategy that addresses these limitations. The OCET system utilizes a photocatalytic TiO₂/Pt film irradiated with perpendicular UV light. An electric field is then generated parallel to the film at the boundary of the patterned UV light, directed from the illuminated region to the dark region. The consequent electrophoresis and electroosmosis work in tandem to move inert colloidal particles (e.g., SiO₂ microspheres) at ∼1 μm/s and trap them a few μm inside the illuminated region along the boundary of the light pattern. By dynamically modulating light patterns, the OCET system achieves directional particle transport and reconfigurable colloidal assembly into arbitrary patterns. The OCET system holds promise for applications in optofluidics, micro/nanorobotics, and biomedical systems, setting the stage for further advancements in optical manipulation technologies.