Light‐Driven Rotation of Plasmonic Nanomotors

Abstract

Colloidal metal nanocrystals exhibit distinct plasmonic resonances that can greatly enhance optical forces and torques. This article highlights the recent application of such particles as light‐driven rotary motors at the nanoscale. By using laser tweezers, it is possible to achieve unprecedented rotation performance in solution, providing a variety of exciting possibilities for applications ranging from nanomechanics to biochemical sensing. Recent developments in this emerging field are discussed, and the physics behind the rotation mechanism, the Brownian dynamics, and the photothermal heating effects influencing the performance of the plasmonic nanomotors are introduced. Possible applications, open questions, and interesting future developments are also discussed.

Recent Advances in Nano‐ and Micromotors

“…Although the developed designs, mobility mechanisms and the envisioned applications are becoming increasingly diverse, they can be categorized into two main types based on whether their self‐propulsion requires source of external energy or rather they carry motors and/or fuel to drive environmentally triggered autonomous locomotion. Externally driven nano‐ and micromotors can be powered by light, ultrasound, as well as magnetic or electric fields . Alternatively, fueled nano‐ and micromotors translate chemical energy into locomotion typically via a catalytic conversion of fuel molecules on their surface .…”

Recent Progress in Optical‐Resonance‐Assisted Movement Control of Nanomotors

“…Because of their strong interaction with light, plasmonic nanocrystals can be tightly trapped in optical tweezers . Under their resonance wavelength, the plasmonic nanocrystal motors in the optical tweezers feel maximized optical rotational torque and achieve fast and stable rotations . The rotation of the plasmonic nanomotors can be driven by laser light with zero photon angular momentum (linear polarization), photon spin angular momentum, and photon orbital angular momentum, respectively.…”

“…Plasmonic rotary nanomotors driven by light with angular momentum. a,b) Plasmonic nanomotors driven by photon spin angular momentum . The optical torques are generated on the plasmonic nanostructures through both absorption and scattering of circularly polarized light (a).…”

“…Under the illumination of laser beams with intensity of 10 mW μm −2 and wavelength of 830 nm, the Au nanosphere and the Au nanorod can rotate to a frequency of 0.6 and 42 kHz, respectively. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…The flagella are powered by protein motors that are adenosine triphosphate or proton‐driven. Inspired by these natural nanometer‐sized biomotors, researchers have developed various artificial nanomotors that are driven by self‐propulsion or external fields. The self‐propulsion is often realized by the mechanisms of self‐electrophoresis, self‐thermophoresis, self‐diffusiophoresis, and chemical‐reaction‐generated bubbles .…”