Opto-thermoelectric microswimmers

Xiaolei Peng,Jie Fang,Pavana Siddhartha Kollipara,Linhan Lin,Yaoran Liu,Zhihan Chen,Yuebing Zheng

doi:10.1038/s41377-020-00378-5

Xiaolei Peng, Jie Fang + Show 5 more

Open Access

https://doi.org/10.1038/s41377-020-00378-5

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Abstract

Inspired by the “run-and-tumble” behaviours of Escherichia coli (E. coli) cells, we develop opto-thermoelectric microswimmers. The microswimmers are based on dielectric-Au Janus particles driven by a self-sustained electrical field that arises from the asymmetric optothermal response of the particles. Upon illumination by a defocused laser beam, the Janus particles exhibit an optically generated temperature gradient along the particle surfaces, leading to an opto-thermoelectrical field that propels the particles. We further discover that the swimming direction is determined by the particle orientation. To enable navigation of the swimmers, we propose a new optomechanical approach to drive the in-plane rotation of Janus particles under a temperature-gradient-induced electrical field using a focused laser beam. Timing the rotation laser beam allows us to position the particles at any desired orientation and thus to actively control the swimming direction with high efficiency. By incorporating dark-field optical imaging and a feedback control algorithm, we achieve automated propelling and navigation of the microswimmers. Our opto-thermoelectric microswimmers could find applications in the study of opto-thermoelectrical coupling in dynamic colloidal systems, active matter, biomedical sensing, and targeted drug delivery.

Highlights

Microswimmers represent a class of micromachines that are able to convert external chemical, acoustic, or electromagnetic energy to swimming motion[1]
Since the first demonstration of catalytic motors in 20042, microswimmers have opened up avenues for diverse biomedical applications, including targeted drug delivery[3,4], precision nanosurgery[5,6], and diagnostic sensing[7,8]
Driven by the thermoelectric field, the Janus particles migrate along the PS-to-Au direction once they are irradiated by a defocused laser beam, which is termed the swimming state

Summary

Introduction

Microswimmers represent a class of micromachines that are able to convert external chemical, acoustic, or electromagnetic energy to swimming motion[1]. Self-propelled microswimmers powered by local chemical energy (e.g., the catalytic decomposition of hydrogen peroxide, which generates hydrogen bubbles for self-propulsion) have been widely studied[9,10,11,12]. Though many optical manipulation techniques, such as optical tweezers, have been employed to transport micro-particles[32,33,34], light-driven microswimmers represent exciting advancements with diverse transport modes (e.g., schooling, gravitaxis, and phototaxis)[35,36,37], adaptive responses to ambient environments and easy light-swimmer coupling, enabling applications in biomedicine, sensing and environmental remediation[38,39,40]

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