Opto-thermoelectric pulling of light-absorbing particles

Abstract

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 mW μm −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.

Opto-Thermophoretic Manipulation

“…To date, this technique exhibits great potential in various fields from freeform optofludic technology to biomedicine as these active objects merit the self-navigation ability in complex biological environments and good biocompatibility. 80,97 Under directional irradiation, light-absorbing particles with low thermal conductivity are able to build a temperature gradient according to the asymmetric heating effect. 36 Figure 6a gives the ionic distributions around an optically heated amorphous Si (a-Si) nanoparticle and the resultant thermoelectric field.…”

“…Interestingly, the self-induced thermoelectric field points against the light-propagating direction to pull the particles against the light flow. 80 It behaves as if the a-Si particles prefer to be heated. Taking advantage of the selfinduced opto-thermoelectric field, the a-Si particles can be trapped in a focused laser spot in 3D at an extremely low optical intensity of 10 −2 mW μm −2 , where the optical scattering force is balanced by the opto-thermoelectric pulling force (Figure 6b).…”

“…Starting from manipulating a mass of particles or molecules in the solution, recent technical innovation has been focused on the trapping and precise control of single tiny objects. More recently, techniques were developed showing that target objects can be manipulated using its self-generated temperature gradient, exhibiting functionalities out-of-reach in contrast to an external temperature gradient. ,− …”

Plasmonic Nanotweezers and Nanosensors for Point‐of‐Care Applications

“…A foreseeable trend for optical manipulation will be to exploit the plasmon‐enhanced optothermal effects, [ 79,154–175 ] which are often regarded as a limit in many plasmonic applications. Optothermal tweezers such as opto‐thermophoretic tweezers and opto‐thermoelectric tweezers turn this limit into an advantage.…”

Optical Trapping, Sensing, and Imaging by Photonic Nanojets

“…Lu et al proved that the photonic nanojet generated by optical trapped microspheres can provide greater light power, making it easier to trap single 10 nm upconversion fluorescence nanoparticle (UCNP) [103]. The particles can be trapped and sensed by optical forces from fiber tweezers or by photophoresis [104][105][106][107][108]. As shown in Figure 4a, three-dimensional trapping and sensing the object can be implemented by combining optical fibers with microspheres [109].…”