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Presented here is a method for actuating a gallium-based liquid-metal alloy without the need for an external power supply. Liquid metal is used as an anode to drive a complementary oxygen reduction reaction, resulting in the spontaneous growth of hydrophilic gallium oxide on the liquid-metal surface, which induces flow of the liquid metal into a channel. The extent and duration of the actuation are controllable throughout the process, and the induced flow is both reversible and repeatable. This self-actuation technique can also be used to trigger other electrokinetic or fluidic mechanisms.

A low-voltage, low-power method of electrically deforming a liquid-metal droplet via the direct manipulation of its surface tension is presented. By imposing a quasi-planar geometry on the liquid metal, its sensitivity to electrocapillary actuation is increased by more than a factor of 40. This heightened responsiveness allows the liquid metal to be deformed at rates exceeding 120 mm/s, greater than an order of magnitude faster than existing techniques for electrical deformation. Significantly, it is demonstrated how this process can be combined with voltage-controlled oxide growth on the surface of non-toxic, gallium-based liquid metals to reversibly form and maintain arbitrary, high-energy shapes.

No abstract

Liquid metal actuated by pressure-driven air bubbles is guided within channels to dynamically reconfigure the length of the radiating aperture and feed line of a slot antenna. The gallium-based liquid metal is held in position by air bubbles, and liquid-metal motion is induced when a pressure differential is created. In contrast to conventional hydraulic or pneumatic actuation of gallium-based liquid metal, the pressure actuation described here is reversible and repeatable, as the liquid metal is enveloped by a thin layer of NaOH solution, which acts as a slip layer and reduces any metal oxidation. The slot antenna achieves a 26% tunable bandwidth with a contiguous range from 1.42 to 1.84 GHz for which the S 11 is <−10 dB. The peak gain ranges from 4.8 dBi in its lowest-frequency state to 4.1 dBi in its highest-frequency state.