Micro-scale opto-thermo-mechanical actuation in the dry adhesive regime

Realizing optical manipulation of microscopic objects is crucial in the research fields of life science,condensed matter physics,and physical chemistry.In non-liquid environments,this task is commonly regarded as difficult due to strong adhesive surface force(~µN)attached to solid interfaces that makes tiny optical driven force(~pN)insignificant.Here,by recognizing the microscopic interaction mechanism between friction force—the parallel component of surface force on a contact surface—and thermoelastic waves induced by pulsed optical absorption,we establish a general principle enabling the actuation of micro-objects on dry frictional surfaces based on the opto-thermo-mechanical effects.Theoretically,we predict that nanosecond pulsed optical absorption with mW-scale peak power is sufficient to tameµN-scale friction force.Experimentally,we demonstrate the two-dimensional spiral motion of gold plates on micro-fibers driven by nanosecond laser pulses,and reveal the rules of motion control.Our results pave the way for the future development of micro-scale actuators in non-liquid environments.