Opto-Thermophoretic Manipulation

Abstract

The optical manipulation of tiny objects is significant to understand and to explore the unknown in the microworld, which has found many applications in materials science and life science. Physically speaking, these technologies arise from direct or indirect optomechanical coupling to convert incident optical energy to mechanical energy of target objects, while their efficiency and functionalities are determined by the coupling behavior. Traditional optical tweezers stem from direct light-to-matter momentum transfer, and the generation of an optical gradient force requires high optical power and rigorous optics. As a comparison, the opto-thermophoretic manipulation techniques proposed recently originate from high-efficiency opto-thermomechanical coupling and feature low optical power. Through rational design of the light-generated temperature gradient and exploring the mechanical response of diverse targets to the temperature gradient, a variety of opto-thermophoretic techniques were developed, which exhibit broad applicability to a wide range of target objects from colloid materials to biological cells to biomolecules. In this review, we will discuss the underlying mechanism of thermophoresis in different liquid environments, the cutting-edge technological innovation, and their applications in colloidal science and life science. We also provide a brief outlook on the existing challenges and anticipate their future development.

Self-thermophoresis of laser-heated spherical Janus particles

“…When (solid line), the northern hemisphere acts as a conductor and thus there is a moderate decrease in the temperature from the heated southern hemisphere of to the unheated northern hemisphere of . This finding supports previous approximations of uniform temperature distributions inside the different zones of the JP under similar conditions [ 11 ]. However, when (dashed line), the role of the northern hemisphere as an insulator leads to a smaller surface area, where heat can effectively escape from the southern hemisphere.…”

“…The thermophoretic mobility of polystyrene can be taken as and for gold [ 15 ]. These values are compatible with the value of taken for a dielectric spherical NP [ 11 ]. Since the coefficients of the metallic and dielectric phases are of the same order and following ‘Appendix B’, one can approximate for the AU/PS JP .…”

“…Selfpropulsion mechanism in micro-systems is generally associated with the conversion of some local chemical (catalytic) energy source [2] or with different means of external incitements, such as imposed electric and magnetic fields, ambient concentration and temperature gradients, ultrasonic and acoustic waves as well as light-induced Joule heating [3,4]. Much attention has been devoted to laser-heated or lightinduced thermophoretic transport of catalytic [5][6][7] and non-catalytic micro-motors (see recent reviews [8][9][10][11]). Achieving a finite thermophoretic velocity of a light-activated homogeneous symmetric colloid (e.g.…”

Plasmonic optical fiber for bacteria manipulation—characterization and visualization of accumulation behavior under plasmo-thermal trapping

“…lenses, beam shaping optics, scanners, etc.) at the point of delivery [ 23 , 24 ]. Nevertheless, challenges lie ahead to develop more reliable, repeatable and simple methods for fabrication of plasmonic devices for bacteria swarm manipulation, particularly to enable potential in vivo applications.…”

Force measurement goes to femto-Newton sensitivity of single microscopic particle

“…Optical tweezers may not be suitable for long-time trapping of objects owing to the photo-induced damage or heating 4 . Compound manipulation is the most effective way to alleviate these limitations, such as magneto-optical, opto-thermophoretic, and opto-hydrodynamic 5 – 7 . Based on the optical and hydrodynamic manipulations, the optically controlled hydrodynamic manipulations have been proposed to trap and observe microscopy objects 6 , 7 .…”