Colloidal Robotics

Colloidal robots refer to the colloid scale (from nm to μm) machines capable of carrying out programmed actions for complex tasks automatically. Because of its promising application in engineering and medical service, colloidal robotics have been of much recent research interest in both theoretical and technological relevance. However, there remain many open challenges on increasing actuation efficiency, achieving high level tasks (e.g., autonomous navigation), etc. This dissertation, in general, focuses on developing new actuation mechanisms and designing autonomous navigation strategies for colloidal robots with both experimental and computational efforts. Firstly, the motivation, background and recent research advances on colloidal robots are reviewed. In Chapter 2, a high-efficiency actuation method called contact charge electrophoresis(CCEP) is introduced to propel the dielectric metallic Janus colloid particles. The autonomous propulsion of Janus particles shows colloidal particle asymmetries can be used to direct the motions of colloidal robots. Beyond single colloidal particle's propulsion, Chapter 3 shows multi-colloidal particles' motions can be coupled and synchronized to generate traveling waves via electrostatic interactions. Our results in Chapter 3 suggest that simple energy inputs can coordinate complex motions for colloidal robots. Then inspired by active particles motions' guided by their symmetry in Chapter 2, we show in Chapter 4 how multiple autonomous navigation can be achieved by designing the active particle's geometry and its stimulus response. Chapter 4 describes a strategy that colloid particles can sense the stimulus in environment via shape-shifting. The feedback loop of sensing and motion enables colloid particles to achieve positive or negative chemotaxis-like navigation. To experimentally realize similar navigation behaviors introduced in Chapter 4, we described a magnetic driven colloidal robot system in Chapter 5, which could show navigation behaviors (uphill and downhill) on a slope by rationally programming the external magnetic field. Chapter 6 highlights future research directions and potential applications of colloidal robots.