Optical trapping and manipulation of colloidal particles and biological objects have demonstrated essential applications in the fields of physical chemistry, biology and condensed matter physics. Currently, most optical tweezers and manipulation techniques are operated in solutions, where undesired Brownian motion will limit the working performance. Herein, we develop an all-optical technique for dynamic manipulation of colloidal particles and nanowires on a solid-state substrate under ambient conditions. Specifically, particles and nanowires are dispersed onto a thin layer of polymer surfactant spin-coated on the glass substrate. The surfactant layer acts as a gate to effectively trigger the particle motion. When the laser is off, particles are firmly bonded on the substrate by van der Waals interactions; under the laser illumination, the photothermal effects of particles induce the transition of polymer layer into a fluid-like phase, which reduces the van der Waals bonding and activates the movement of nanoparticles by optical scattering forces. This optothermally gated photon nudging strategy supports on-demand manipulation and reconfigurable patterning of colloidal particles at nanoscale accuracy with simple optics and low operation power. Our method applies to particles with different materials (e.g., gold, silver, silicon) and variable sizes (from 40 nm to 1.5 mm). Furthermore, integrated with dark-field imaging and spectroscopy, the reported platform enables in-situ detection and characterizations of the colloidal structures. With its versatile capabilities, this novel nanomanipulation technique will have promising applications in optical nanomanufacturing, nanophotonics, and colloidal nanodevices.
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