Fabrication of 3D Printed Thermoelectric Devices for Integration Into Liquid Crystal Elastomer Actuators

Abstract Shape memory materials such as liquid crystal elastomers (LCE) have been explored as soft robotic actuators due to their high mechanical robustness and muscle-like work densities. The main drawback of LCEs is slow response times and low energy efficiencies stemming from poor thermal management. Thermoelectric devices (TED), which generate temperatures differentials across semiconductors through the Peltier effect when current is applied, have the potential to address these long response times. By introducing additive manufacturing along with conductive liquid metal (LM) traces, we introduce TED for soft robotic applications. In this study, we build on recent work in soft thermoelectric generators to create high density arrays of thermoelectric semiconductors to actively heat and cool LCEs. We describe advancements in the manufacturing of a soft TED in which we achieve a 28% fill factor of semiconductors through the use of 3D printing. We report maximum power densities of 236 μWcm−2 at ΔT = 60 °C. By coating LCE on each side of the TED we create single input multidirectional liquid crystal elastomer thermoelectric device (LCE-TED) actuators. Thermal management design challenges are discussed along with the introduction of liquid metal embedded elastomer composites (LMEE) into TED design. Lastly, we introduce an inchworm inspired soft robot walker based on these LCE-TED actuators. We highlight gait mechanics for three cycles of actuation for this soft robotic system.