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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. 

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 self-induced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-a-chip devices. 

Abstract The capabilities of manipulating and analyzing biological cells, bacteria, viruses, deoxyribonucleic acids (DNAs), and proteins at high resolution are significant in understanding biology and enabling early disease diagnosis. The progress in developments and applications of plasmonic nanotweezers and nanosensors is discussed, where the plasmon‐enhanced light‐matter interactions at the nanoscale improve the optical manipulation and analysis of biological objects. Selected examples are presented to illustrate their design and working principles. In the context of plasmofluidics, which merges plasmonics and fluidics, the integration of plasmonic nanotweezers and nanosensors with microfluidic systems for point‐of‐care (POC) applications is envisioned. Perspectives on the challenges and opportunities in further developing and applying the plasmofluidic POC devices are provided. 

Abstract Since the first discovery of graphene, 2D materials are drawing tremendous attention due to their atomic thickness and superior properties. Fabrication of high‐quality micro‐/nanopatterns of 2D materials is essential for their applications in both nanoelectronics and nanophotonics. In this work, an all‐optical lithographic technique, optothermoplasmonic nanolithography (OTNL), is developed to achieve high‐throughput, versatile, and maskless patterning of different atomic layers. Low‐power (≈5 mW µm⁻²) and high‐resolution patterning of both graphene and MoS₂monolayers is demonstrated through exploiting thermal oxidation and sublimation at the highly localized thermoplasmonic hotspots. Density functional theory simulations reveal that Au nanoparticles reduce the formation energy (≈0.6 eV) of C monovacancies through bonding between undercoordinated C and Au, leading to a significant Au‐catalyzed graphene oxidation and a reduction of the required laser operation power. Programmable patterning of 2D materials into complex and large‐scale nanostructures is further demonstrated. With its low‐power, high‐resolution, and versatile patterning capability, OTNL offers the possibility to scale up the fabrication of nanostructured 2D materials for many applications in photonic and electronic devices.