When immersed in an electrolyte, droplets of Ga‐based liquid metal (LM) alloy can be manipulated in ways not possible with conventional electrocapillarity or electrowetting. This study demonstrates how LM electrochemistry can be exploited to coalesce and separate droplets under moderate voltages of ~1–10 V. This novel approach to droplet interaction can be explained with a theory that accounts for oxidation and reduction as well as fluidic instabilities. Based on simulations and experimental analysis, this study finds that droplet separation is governed by a unique limit‐point instability that arises from gradients in bipolar electrochemical reactions that lead to gradients in interfacial tension. The LM coalescence and separation are used to create a field‐programmable electrical switch. As with conventional relays or flip‐flop latch circuits, the system can transition between bistable (separated or coalesced) states, making it useful for memory storage, logic, and shape‐programmable circuitry using entirely liquids instead of solid‐state materials.

We examine the flexural deformation and snap-through instability of a pre-buckled ferroelastomer beam. The beam is composed of ferromagnetic and electrically conductive microparticles suspended in a polydimethylsiloxane (PDMS) matrix. Bending and snap-through are controlled remotely with an external magnetic field. The observed magneto-flexural coupling is in reasonable agreement with predictions from an analytic model based on elastic rod theory and variational techniques. Moreover, such coupling results in stable and unstable bending modes that can be exploited for a soft-matter, field-controlled, reconfigurable electrical relay. These two flexural modes correspond to (i) low-power binary (stable) switching and (ii) a more rapid >10Hz response that is achieved by momentarily driving the beam to a slightly deformed configuration. This combination of stable and unstable switching states provides a new approach for harnessing elastic instabilities and a means to create a low power, yet rapidly responsive switch for soft electronic systems

Submersible robotics have improved in efficiency and versatility by incorporating features found in aquatic life, ranging from thunniform kinematics to shark skin textures. To fully realize these benefits, sensor systems must be incorporated to aid in object detection and navigation through complex flows. Again, inspiration can be taken from biology, drawing on the lateral line sensor systems and neuromast structures found on fish. To maintain a truly soft-bodied robot, a man-made flow sensor must be developed that is entirely complaint, introducing no rigidity to the artificial “skin.” We present a capacitive cupula inspired by superficial neuromasts. Fabricated via lost wax methods and vacuum injection, our 5 mm tall device exhibits a sensitivity of 0.5 pF/mm (capacitance versus tip deflection) and consists of room temperature liquid metal plates embedded in a soft silicone body. In contrast to existing capacitive examples, our sensor incorporates the transducers into the cupula itself rather than at its base. We present a kinematic theory and energy-based approach to approximate capacitance versus flow, resulting in equations that are verified with a combination of experiments and COMSOL simulations.