Remote control of heat nanosources motion and thermal-induced fluid flows by using light forces (IMAGE)
Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS
Caption
a, Multiple gold NPs (spheres of 200 nm radius) are confined by a ring-shaped laser trap (wavelength of 532 nm) and optically transported around it. These NPs rapidly assemble into a stable group of hot particles creating a confined heat source (G-NP) of temperature ~500 K. Free (not trapped) gold NPs acting as tracer particles are dragged toward the G-NP by the action of the thermal-induced water flow created around it (see Video S5 of the paper). The speed of the G-NP is controlled by the optical propulsion force which is proportional to the phase gradient strength tailored along the laser trap as displayed in b, corresponding to the transport state 1. This non-uniform propulsion force drives the G-NP reaching a maximum speed of 42 μm/s. b, Sketch of the switching of the phase gradient configuration (state 1 and 2) enabling a more sophisticated manipulation of the heat source: split and merge of the G-NP. (c), The opposite averaged propulsion forces in the split region (see state 3 at ~0 deg, shown in b) separate the NPs belonging to the original G-NP thus creating G-NP1 and G-NP2, as observed in the displayed sequence (see Video S6 of the paper). These two new heat sources are propelled by the time averaged propulsion force corresponding to state 3 in opposite directions toward the region where they finally merge into a joint G-NP again. Complex transport trajectories for G-NP delivery, for example in form of knot circuit (see Video S7 of the paper), can be created enabling spatial distribution of moving heat sources across a target network
Credit
by José A. Rodrigo, Mercedes Angulo and Tatiana Alieva
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