Highly Thermally Conductive Bimorph Structures for Low-Grade Heat Energy Harvester and Energy-Efficient Actuators

Low-power electronics are urgently needed for various emerging technologies, e.g., actuators as signal transducers and executors. Collecting energy from ubiquitous low-grade heat sources (T< 100 °C) as an uninterrupted power supply for low-power electronics is highly desirable. However, the majority of energy-harvesting systems are not capable of collecting low-grade heat energy in an efficient and constant manner. Limited by materials and driving mode, fabrications of low-power and energy-efficient actuators are still challenging. Here, highly thermally conductive bimorph structures based on graphene/poly(dimethylsiloxane) (PDMS) structures have been fabricated as low-grade heat energy harvesters and energy-efficient actuators. Regular temperature fluctuations on bimorph structures can be controlled by nonequilibrium heat transfer, leading to stable and self-sustained thermomechanical cycles. By coupling ferroelectric poly(vinylidene fluoride) with bimorph structures, uninterrupted thermomechanoelectrical energy conversion has been achieved from the low-grade heat source. Utilizing the rapid thermal transport capability, multifinger soft grippers are assembled with bimorph actuators, demonstrating fast response, large displacement, and adaptive grip when driven by low-temperature heaters.