Liquid metal logic for soft robotics

While there are many soft matter sensing and actuation technologies, there is far less choice when it comes to soft material devices for control and computation. One solution is the Soft Matter Computer (SMC) which can perform both analogue and digital computations in soft materials. This computer processes a fluidic input pattern, consisting of alternating regions of conducting and insulating fluids into an electronic output signal. However, the use of salt water as the conductive fluid means that the Soft Matter Computer has high electrical resistance and requires an AC voltage, making untethered operation impractical. In this paper, we introduce the liquid metal Soft Matter Computer (LM-SMC), which uses galinstan as an alternative conductive fluid. We show that by switching to a liquid metal-sodium hydroxide fluidic input, we reduce the electrical resistance of the SMC by three orders of magnitude, allowing operation at DC voltages of 2 Volts and under. We characterise the stability of the liquid metal input patterns and demonstrate the potential of the LM-SMC by using it to control bipolar ionic polymer metal composite and shape memory alloy actuators. By enabling fully soft computation and control of multiple actuators from a single low voltage DC source, the LM-SMC enables a new class of intelligent and untethered soft machines.