Pose Control of Millimeter-Scale Objects in a Laser-Powered Thermocapillary Manipulation Platform

The miniaturization of technological components requires tools capable of manipulating them. Non-contact micromanipulation has recently gained popularity since it minimizes component damage and adhesion problems. However, the simultaneous position and orientation (pose) control using noncontact tools remains an open challenge. In this work, we propose the pose control of millimeter-scale structures at the air-water interface using laser-powered thermocapillary flows. We achieve autonomous pose control by steering two laser spots around the structure in a closed-loop manner. The controller consists of a linear pose controller and a model inversion. The pose controller defines the required force and torque to reach the target. The model inversion defines the required laser positions to obtain said force and torque. This inversion is performed with an optimization algorithm, without any prescribed strategy. The pose stabilization was validated experimentally, obtaining a position and orientation precision of 0.15 body lengths and 2 degrees, respectively. Additionally, we show the experimental path-following with independent orientation control, obtaining a similar position precision.