Remote Photothermal Actuation of Underwater Bubble toward Arbitrary Direction on Planar Slippery Fe3O4-Doped Surfaces

Unidirectional underwater gas bubble (UGB) transport on a surface is realized by buoyant force or wettability gradient force (Fwet-grad) derived from a tailored geography. Unfortunately, intentional control of the UGB over transport speed, direction, and routes on horizontal planar surfaces is rarely explored. Herein reported is a light-responsive slippery lubricant-infused porous surface (SLIPS) composed of selective lubricants and super-hydrophobic micropillar-arrayed Fe3O4/polydimethylsiloxane film. Upon this SLIPS, the UGB can be horizontally actuated along arbitrary directions by remotely loading/discharging unilateral near-infrared (NIR) stimuli. The underlying mechanism is that Fwet-grad can be generated within 1 s in the presence of a NIR-trigger due to the photothermal effect of Fe3O4. Once the NIR-stimuli are discharged, Fwet-grad vanishes to break the UGB on the SLIPS. Moreover, performed are systematic parameter studies to investigate the influence of bubble volume, lubricant rheology, and Fwet-grad on the UGB steering performance. Fundamental physics renders the achievement of antibuoyancy manipulation of the UGBs on an inclined SLIPS. Significantly, steering UGBs by horizontal SLIPS to configurate diverse patterns, as well as facilitating light-control-light optical shutter, is deployed. Compared with the previous slippery surfaces, light-responsive SLIPS is more competent for manipulating UGBs with controllable transport speed, direction, and routes independent of buoyancy or geography derivative force.