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By combining metallic electrical conductivity with low viscosity, liquid metals and liquid metal alloys offer new and exciting opportunities to serve as reconfigurable components of electronic, microfluidic, and electromagnetic devices. Here, we review the physics and applications of techniques that utilize voltage to manipulate the interfacial tension of liquid metals; such techniques include electrocapillarity, continuous electrowetting, electrowetting-on-dielectric, and electrochemistry. These techniques lower the interfacial tension between liquid metals and a surrounding electrolyte by driving charged species (or in the case of electrochemistry, chemical species) to the interface. The techniques are useful for manipulating and actuating liquid metals at sub-mm length scales where interfacial forces dominate. We focus on metals and alloys that are liquid near or below room temperature (mercury, gallium, and gallium-based alloys). The review includes discussion of mercury—despite its toxicity—because it has been utilized in numerous applications and it offers a way of introducing several phenomena without the complications associated with the oxide layer that forms on gallium and its alloys. The review focuses on the advantages, applications, opportunities, challenges, and limitations of utilizing voltage to control interfacial tension as a method to manipulate liquid metals.

Standing waves have been parametrically excited on an interface between mercury and aqueous salt solutions by periodic electrical polarization of the interface. The waves obey the known dispersion relation for capillary‐gravity waves. The variation of the interfacial tension with the bias voltage across the interface has been measured, and displays the expected quadratic dependence. Various aspects of the excitation mechanism are shown to be in accord with theoretical expectation.

Langmuir-Blodgett films (LB-films) consist from few LB-monolayers which are high structured nanomaterials that are very promising materials for applications. We use a geometrical approach to describe structurization into LB-monolayers. Consequently, we develop on the 1-jet space J 1 ([0,∞),R 2 ) the single-time Lagrange geometry (in the sense of distinguished (d-) connection, d-torsions and an abstract anisotropic electromagnetic-like d-field) for the Lagrangian governing the 2D-motion of a particle of monolayer. One assumed that an expansion near singular points for the constructed geometrical Lagrangian theory describe phase transitions to LB-monolayer. Trajectories of particles in a field of the electrocapillarity forces of monolayer have been calculated in a resonant approximation utilizing some Jacobi equations. A jet geometrical Yang-Mills energy is introduced and some computer graphic simulations are exposed.

This letter describes an ultrahigh contrast valve driven by the electrocapillarity of liquid gallium. We demonstrate that a micrometer-sized gallium droplet can be used to fabricate a prototype backlight transmissive pixel cell by transforming the droplet into a flat thin film. This light valve exhibits significantly high backlight utility (96%), an exceptional contrast ratio (106:1), and fast response time (0.49 ms). The high contrast ratio originated from the exceptional reflectivity of gallium, which can block backlight to prevent any transmission in the off state of our device. Without using any polarizer, the backlight utility can be improved dramatically compared to a conventional liquid crystal display. The backlight utility and switching time obtained from this prototype light valve is higher than that of commercial liquid crystal displays. This concept is also applicable to a wide variety of electro-optical devices.

The first phase of a systematic study of the electrochemical phenomena at the metal‐gas interface is presented. An experimental and theoretical analysis of the phenomenon of electrocapillarity at the metal‐gas interface is described. Experimental curves of the relative reduction of surface tension vs applied potential were obtained at the interface between a mercury electrode and vacuum or He, HBr, and ethanol at various bulk pressures. The electrocapillary curves resemble the theoretical electrocapillary curves obtained from first principles. The potential of the maximum surface tension is at zero voltage. At 4 kV the surface tension decreases significantly. The variation in the surface tension at this voltage is about 100 erg cm−2. The electrocapillary curve at the mercury‐He interface approaches the ’’vacuum’’ curve. The effect of ethanol involves an absolute depression of the surface tension, but the general shape remains the same as that of He. The HBr curve differs from all others due to surface rea...

An optical modulator based on the electrocapillarity effect has been built and demonstrated. Optically, the device consists of a plane, variable radius circular mirror formed by the contact of mercury and a glass sheet. The mercury is also in contact with an aqueous electrolyte, and the diameter of the mirror is switched between two stable values by applying voltage pulses to the mercury/electrolyte interface. Switching times of 3 ms have been observed.