Abstract
Utilization of ubiquitous low-grade waste heat constitutes a possible avenue towards soft matter actuation and energy recovery opportunities. While most soft materials are not all that smart relying on power input of some kind for continuous response, we conceptualize a self-locked thermo-mechano feedback for autonomous motility and energy generation functions. Here, the low-grade heat usually dismissed as ‘not useful’ is used to fuel a soft thermo-mechano-electrical system to perform perpetual and untethered multimodal locomotions. The innately resilient locomotion synchronizes self-governed and auto-sustained temperature fluctuations and mechanical mobility without external stimulus change, enabling simultaneous harvesting of thermo-mechanical energy at the pyro/piezoelectric mechanistic intersection. The untethered soft material showcases deterministic motions (translational oscillation, directional rolling, and clockwise/anticlockwise rotation), rapid transitions and dynamic responses without needing power input, on the contrary extracting power from ambient. This work may open opportunities for thermo-mechano-electrical transduction, multigait soft energy robotics and waste heat harvesting technologies.
Highlights
Utilization of ubiquitous low-grade waste heat constitutes a possible avenue towards soft matter actuation and energy recovery opportunities
The thermo-mechanoelectrical system (TMES) mainly consists of a three-dimensionally (3D) aligned ferroelectric polyvinylidene fluoride (PVDF) and polydopamine modified reduced graphene oxide-carbon nanotube layer (PDG-CNT) with nacre-like brick-and-mortar microstructures[37]
A direction characterized by anticlockwise angular offset α is defined here as the angle between the longitudinal alignment direction of PVDF and the length direction of TMES strip (Supplementary Fig. 5)
Summary
Utilization of ubiquitous low-grade waste heat constitutes a possible avenue towards soft matter actuation and energy recovery opportunities. Unless the external stimulus is repeatedly switched on-off, they face limitations in performing repetitive macroscopic motion at high actuation speed under a constant/invariant operation mode. This underscores the significance to address both the material design and system concept in transposing energy invariant waste/residual heat into diverse mechanical motions, one that is perpetual and self-propelled automation. The untethered TMES can be fueled by a constant low-grade heat source, and selfpropelled by an intrinsic built-in thermo-mechanical and mechano-thermal feedback loops, performing perpetual and multimodal locomotions, such as high-frequency translational oscillation, clockwise/anticlockwise rotational, and revolving motor-like motions. To meet the foregoing demands of soft actuator that imitates the softness, agility, and self-moving living organisms, a prototypical soft robot termed TMES-bot is sought to reproduce bioinspired self-defensive locomotions with additional power-generating functionality, which can possibly operate in an unstructured outdoor environment
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