(323g) High Speed Controlled Propulsion of Wheel Shaped Microbead Assemblies

Microbot propulsion is hindered because macroscopic swimming mechanisms are ineffective as viscosity plays a dominant role at small length scales. Microorganisms overcome these limitations through physical adaptations, including flagellum, that are difficult to artificially replicate and control. To address this, we demonstrate how colloidal particles can be assembled into wheel-shaped microstructures (microwheels) via external magnetic fields and showed that the microwheels can roll along surfaces at speeds of up to 0.1 mm/s. To investigate propulsion mechanisms, both magnetic field and microwheel size was varied. For quantification, microwheel propulsion was recorded using a high-speed camera and parameters including speed, rotational frequency and tilt angle measured using custom image processing code. Control of direction was achieved both automatically and manually using a keyboard with custom control software. With ease of assembly, high speed and precise directional-control, colloidal microwheels provide a useful tool for microcargo delivery applications.