Abstract
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 letter, 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.
Highlights
The advantages of using soft materials in robotics has led to the introduction of a plethora of soft material mechanisms for sensing and actuation [1]–[5]
We have shown that liquid metal is a superior conductive fluid for the soft matter computer, provided a sufficiently low DC voltage is used
We have investigated the use of liquid metal as a novel conducting fluid for the input of a soft matter computer
Summary
The advantages of using soft materials in robotics has led to the introduction of a plethora of soft material mechanisms for sensing and actuation [1]–[5]. The second main approach to controlling soft material robots - embodied control - exploits the mechanical intelligence of the robot’s body to produce behaviours. An AC voltage source was required to prevent electrolysis of the salt water and consequent disruption of the input pattern This requirement added complexity to the SMC drive electronics, and meant SMC controlled soft robots were either tethered, or included additional rigid electronic components. We introduce the liquid metal Soft Matter Computer (LM-SMC), which replaces the salt water with liquid metal, reducing the electrical resistance by three orders of magnitude and eliminating the need for an AC voltage source Together, these benefits make the LM-SMC a step towards a new class of intelligent and untethered soft machines. Actuators, which require DC voltages for bi-directional control, are switched between in- and out-of phase beating
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