Precise and Omnidirectional Opto-Thermo-Elastic Actuation in Van Der Waals Contacting Systems.

Actuation of micro-objects along unconstrained trajectories in van der Waals contacting systems-in the same capacity as optical tweezers to manipulate particles in fluidic environments-remains a formidable challenge due to the lack of effective methods to overcome and exploit surface friction. Herein, a technique that aims to resolve this difficulty is proposed. This study shows that, by utilizing a moderate power beam of light, micro-objects adhered on planar solid substrates can be precisely guided to move in arbitrary directions, realizing sub-nanometer resolution across extended surfaces. The underlying mechanism is the interplay between surface friction and pulsed opto-thermo-elastic deformations, and to render a biased motion with off-centroid light illumination. This technique enables high-precision assembly, separation control of nanogaps, regulation of rotation angles in various material-substrate systems, whose capability is further tested in reconfigurable construction of optoelectronic devices. With simple set-up and theoretical generality, opto-thermo-elastic actuation opens up an avenue for versatile optical manipulation in the solid domain.