Optomechanics arises from the photon momentum and its exchange with low-dimensional objects.It is well known that optical radiation exerts pressure on objects,pushing them along the light path.However,optical pulling ...Optomechanics arises from the photon momentum and its exchange with low-dimensional objects.It is well known that optical radiation exerts pressure on objects,pushing them along the light path.However,optical pulling of an object against the light path is still a counter-intuitive phenomenon.Herein,we present a general concept of optical pulling-opto-thermoelectric pulling(OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path.This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles,and three-dimensional(3D)trapping of single particles is achieved at an extremely low optical intensity of 10^(−2)mWμm^(−2).Moreover,the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance.The concept of selfinduced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-achip devices.展开更多
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 electri...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 optothermoelectric microswimmers could find applications in the study of opto-thermoelectrical coupling in dynamic colloidal systems,active matter,biomedical sensing,and targeted drug delivery.展开更多
基金the financial support of the National Science Foundation(NSF-CMMI-1761743)the Army Research Office(W911NF-17-1-0561)+4 种基金the National Aeronautics and Space Administration Early Career Faculty Award(80NSSC17K0520)the National Institute of General Medical Sciences of the National Institutes of Health(DP2GM128446)financial support of this work from the Robert A.Welch Foundation(Grant no.F-1464)the National Science Foundation through the Center for Dynamics and Control of Materials:an NSF MRSEC under Cooperative Agreement No.DMR-1720595support from the Youth Thousand Talent Programme of China.
文摘Optomechanics arises from the photon momentum and its exchange with low-dimensional objects.It is well known that optical radiation exerts pressure on objects,pushing them along the light path.However,optical pulling of an object against the light path is still a counter-intuitive phenomenon.Herein,we present a general concept of optical pulling-opto-thermoelectric pulling(OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path.This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles,and three-dimensional(3D)trapping of single particles is achieved at an extremely low optical intensity of 10^(−2)mWμm^(−2).Moreover,the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance.The concept of selfinduced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-achip devices.
基金the financial support of the Army Research Office(W911NF-17-1-0561)the National Science Foundation-Civil,Mechanical and Manufacturing Innovation(1761743)+2 种基金the National Aeronautics and Space Administration(80NSSC17K0520)the National Institute of General Medical Sciences of the National Institutes of Health(DP2GM128446)financial support from the State Key Laboratory of Precision Measurement Technology and Instruments.
文摘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 optothermoelectric microswimmers could find applications in the study of opto-thermoelectrical coupling in dynamic colloidal systems,active matter,biomedical sensing,and targeted drug delivery.
