Optothermal rotation of micro-/nano-objects in liquids

TL;DR

This paper reviews recent advances in optothermal rotation of micro-/nano-objects in liquids, highlighting various physical mechanisms, applications, and future challenges in the field.

Contribution

It categorizes optothermal rotation techniques based on physical mechanisms and discusses recent progress, including applications in biology and nanorobotics.

Findings

Multiple physical mechanisms enable optothermal rotation.

Applications include single-cell mechanics and 3D bio-imaging.

The review identifies challenges and future directions.

Abstract

Controllable rotation of micro-/nano-objects provides tremendous opportunities for cellular biology, three-dimensional (3D) imaging, and micro/nanorobotics. Among different rotation techniques, optical rotation is particularly attractive due to its contactless and fuel-free operation. However, optical rotation precision is typically impaired by the intrinsic optical heating of the target objects. Optothermal rotation, which harnesses light-modulated thermal effects, features simpler optics, lower operational power, and higher applicability to various objects. In this Feature Article, we discuss the recent progress of optothermal rotation with a focus on work from our research group. We categorize the various rotation techniques based on distinct physical mechanisms, including thermophoresis, thermoelectricity, thermo-electrokinetics, thermo-osmosis, thermal convection, and thermo-capillarity. Benefiting from the different rotation modes (i.e., in-plane and out-of-plane rotation), diverse applications in single-cell mechanics, 3D bio-imaging, and micro/nanomotors are demonstrated. We conclude the article with our perspectives on the operating guidelines, existing challenges, and future directions of optothermal rotation.