Dynamic microfluidic control with VO2-based metasurfaces

We present a vanadium dioxide (VO2) metasurface capable of tuning the radiative properties through the insulator-to-metal transition in the atmospheric window. Theoretically, we demonstrate that the hemispherical emissivity approaches near-unity due to the opening of the radiation channel and the Fabry–Pérot mode formed by the multilayer structure. Moreover, when the incident angle is 60°, the average emissivity in the insulating state reaches 0.45, and that in the metallic state reaches 0.64. Additionally, we integrate photothermal conversion and optical tweezers techniques to experimentally demonstrate the generation of thermofluid. The VO2 metasurface generates closed-loop thermal convection vortices with a maximum fluid velocity of ∼10 nm/s. The thermophoretic force (∼100 pN) is three orders of magnitude larger than the optical force (100–400 fN). The thermofluid convection was caused by the asymmetric thermal distribution resulting from the photons absorbed in the heater. The structure we proposed has the potential to be applied in various fields related to thermal control, biochemistry, microwave hyperthermia, nanoparticle transportation, and so on.