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

Weiwei Tang,Jiyong Wang,Wei Yan,Jinsheng Lu,Min Qiu,Wei Lyu,Fengjiang Liu

doi:10.1038/s41377-021-00622-6

Weiwei Tang, Jiyong Wang + Show 5 more

Open Access

https://doi.org/10.1038/s41377-021-00622-6

Copy DOI

Abstract

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 tame µN-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.

Highlights

In his landmark lecture “There is plenty of room at the bottom” in 1959, Richard Feynman envisioned a fundamental scaling challenge in the coming era of nanotechnology: macroscopic designing rules for mechanical devices shall become invalid at micro-scales where adhesive surface force plays a dominant role in the mechanical response of devices as a result of increased surface-tovolume ratio[1]
A few recent studies have pointed out a new direction: the excitations of elastic waves in microobjects could facilitate their locomotion on dry surfaces[22,23,24], as an extension of macroscopic surface elastic-wave motors[25,26]
We start with a case study to pedagogically interpret the principle of the proposed micro-scale opto-thermomechanical actuation scheme and to clarify the key role of elastic waves—excited by mild optical absorption—in overcoming friction force

Summary

Introduction

In his landmark lecture “There is plenty of room at the bottom” in 1959, Richard Feynman envisioned a fundamental scaling challenge in the coming era of nanotechnology: macroscopic designing rules for mechanical devices shall become invalid at micro-scales where adhesive surface force plays a dominant role in the mechanical response of devices as a result of increased surface-tovolume ratio[1] To bypass this challenge, the micro-scale mechanical devices, especially actuators—indispensable in various applications, such as optical communications[2,3,4,5], optical displays[6] and molecular cargo7,8—, nowadays generally exploit membrane architecture to mitigate undesirable surface effects and employ scale-invariant electrostatic force[9,10]. The findings in these studies have demonstrated motions of specificshaped gold plates either along the azimuthal[23] or axial directions[22,24] of the micro-fibers, but not both

Methods

Results

Conclusion