VALP: Vision-Based Adaptive Laser Propulsor for Noncontact Manipulation at the Air–Liquid Interface

Noncontact manipulation at the air–liquid interface holds vast potential applications in biochemistry analysis, flexible electronics, micromanufacturing, and microrobotics. The universal and versatile control of passive floating objects remains a great challenge. Here, we present a vision-based adaptive laser propulsor (VALP) system for the motion control of generalized millimeter-scale floating objects. The VALP system actuates the floating objects directionally through parallel thermocapillary flows induced by ultrafast laser scanning. A simplified kinetic model is developed to simulate the dynamic response of floating objects in the VALP system, and corresponding gains are proven effective in closed-loop control experiments for stationary target positioning and complex trajectory replication. The maximum velocity of the floating object reaches 13.9 mm/s, while its position-holding error for the intended target maintains within 0.48 mm. The trajectory replication error for a typical Lissajous curve is below 0.4 mm. Multiple objects can be manipulated simultaneously through the ultrafast scanning and multiplexing of the laser beam. Adaptability is validated in multiple generalization experiments for floating objects with different sizes, materials, shapes, and other characteristics. With the capability of highly directional propulsion, the VALP system enables smooth, fast, precise, and adaptive closed-loop motion control of generalized floating objects without the need for their prior information, promising it as a universal and versatile platform for noncontact manipulation at the air–liquid interface.