Light-propelled dimeric micro-rotor in a binary critical mixture

Abstract

Industrial motors produce either linear or rotational motion, and enabling these engines on micrometer scales would have significant technological implications in the biomedical, biochemical, nanoscience, and nanotechnology areas. In this paper, we report a colloidal dimeric micro-rotor consisting of a pivot particle (isotropic dielectric particle) joined to a carbon Janus particle (anisotropic particle) embedded in a critical mixture. The two particles forming this dimer are trapped and illuminated by an optical tweezer, respectively. The carbon Janus particle heats its surroundings, producing a demixing flow that results in directed rotational motion. The pivot ensures the stability of the dimer’s rotation motion, allowing for a clean circular trajectory with low dispersion between cycles. This system converts thermal energy from the absorption of light by the carbon Janus particle into mechanical rotational work. By adjusting the laser power input energy, we obtained rotational work values ranging from 3300 to 270 kBT per cycle. However, there is a limit in the laser power that induces rotation, which depends on the balance between trapping and demixing forces required for stable rotation. This paper provides an efficient method to construct a rotational micro-rotor with a stable motion (standard deviation = 0,03 µm) for nano and micro devices.