EML webinar overview: Liquid metals at the extreme

Gallium-based liquid metals are often overlooked despite their remarkable properties: melting points below room temperature, water-like viscosity, low-toxicity, and effectively zero vapor pressure (they do not evaporate). They also have, by far, the largest interfacial tension of any liquid at room temperature. Normally small volumes of liquids with large tension form spherical or hemi-spherical structures to minimize surface energy. Yet, these liquid metals can be patterned and printed into nonspherical shapes (cones, wires, antennas, circuits) due to a thin, oxide skin that forms rapidly on its surface. The ability to pattern metal enables new types of ultra-stretchable wires, self-healing circuits, and soft logic devices (the latter of which perform logic in a 'distributed' way without conventional semiconductors). Combining liquid metals with elastomer can also lead to emergent and new material properties, such as tough fibers and composites with negative piezopermittivity (decreasing dielectric 'constant' with strain, which is unprecedented) and positive piezoconductivity (increasing conductivity with strain, which is highly unusual). Perhaps the most unexpected aspect of liquid metals it the ability to use interfacial electrochemistry chemistry to remove/deposit the oxide to manipulate the interfacial tension of the metal over unprecedented ranges (from the largest tension of any known liquid to near zero). The properties of liquid metals have implications for soft and stretchable devices with desirable mechanical properties for human-machine interfaces soft robotics, and wearable electronics. EML webinar speakers and videos are updated at https://imechanica.org/node/24098. (C) 2020 Elsevier Ltd. All rights reserved.