Adhesion-assisted nanoscale rotary locomotor in non-liquid environments
arXiv:1804.08063 · doi:10.1126/sciadv.aau8271
Abstract
Rotation in micro/nanoscale provides extensive applications in mechanical actuation, cargo delivery, and biomolecule manipulation. Light can be used to induce a mechanical rotation remotely, instantly and precisely, where liquid throughout serves as a must-have enabler to suspend objects and remove impact of adhesion. Achieving light-driven motion in non-liquid environments faces formidable challenges, since micro-sized objects experience strong adhesion and intend to be stuck to contact surfaces. Adhesion force for a usual micron-sized object could reach a high value (nN - μN) which is several orders of magnitude higher than both its gravity (~ pN) and typical value of optical force (~ pN) in experiments. Here, in air and vacuum, we show counter-intuitive adhesion-assisted rotary locomotion of a micron-sized metal nanoplate with ~30 nm-thickness, revolving around a microfiber. This locomotor is powered by pulsed light guided into the fiber, as a coordinated consequence of photothermally induced surface acoustic wave on the nanoplate and favorable configuration of plate-fiber geometry. The locomotor crawls stepwise with sub-nanometer locomotion resolution actuated by designed light pulses. Furthermore, we can control the rotation velocity and step resolution by varying the repetition rate and pulse power, respectively. A light-actuated micromirror scanning with 0.001° resolution is then demonstrated based on this rotary locomotor. It unfolds unprecedented application potential for integrated micro-opto-electromechanical systems, outer-space all-optical precision mechanics and controls, laser scanning for miniature lidar systems, etc.
13 pages, 5 figures