Near-infrared light propelled motion of needlelike liquid metal nanoswimmers

Abstract

We report a needlelike liquid metal gallium nanoswimmer (LMGNS) with a controllable motion under the exposure of a near-infrared (NIR) laser. The needlelike LMGNS is constructed by a nanoporous template-assisted plastic molding technique. Under the irradiation of a continuous NIR laser, LMGNSs can autonomously move in a direction of tip forward, and their speed could reach up to 31.22 μm s−1 at a laser intensity of 5 W cm−2. The speed of motion and on/off behavior of LMGNSs can be conveniently modulated by controlling the intensity of a NIR laser. Computer simulations reveal that the propulsion of LMGNS is attributed to the self-thermophoresis caused by the temperature gradient along its longitudinal axis, which is induced by the difference of diameters of the two ends. The speed of LMGNS is higher on the substrate with lower surface potential because the thermoosmosis effect, as a resistance, is weaker. Such needlelike liquid metal nanoswimmers have a potential for biomedical applications and active soft matter materials.