Two-Dimensionally Nano-Capsulating Liquid Metal for Self-Sintering and Self-Oscillating Bimorph Composites with Persistent Energy-Harvest Property

Abstract

Harvesting electricity from ubiquitous atmospheric moisture has drawn growing research attention. Despite great advances, moisture generators still suffer from performance decay during long-term service. Recently, self-oscillating actuators driven by humidity gradience have attracted great interests, which may give a clue to harvest energy persistently via electromagnetic induction. In order to combine high electric conductivity with self-oscillating actuators, bimorph composites of 2D conductive MXene with liquid metal (i.e., EGaIn) are designed. In presence of marine alginate, EGaIn droplets can be encapsulated by MXene nanosheets in their suspension. And simple liquid-casting can produce biomorph actuating films with top MXene-rich layer and bottom EGaIn-rich layer of self-sintered EGaIn droplets. When exposing to a humidity gradience (e.g., 20% cm−1), this biomorph actuator can oscillate persistently with an actuating speed of ≈260° s−1 and a frequency of ≈0.5 Hz, while without any human intervention. Under a magnetic field (e.g., intensity ≈0.5 T), this self-oscillating behavior can generate an alternating faradic current with an amplitude of at least 1360 µA m−2. Thus, this study may not only provide an alternative pathway for producing self-oscillating and conductive actuators, but also offer a new strategy for persistent energy harvest from atmospheric moisture.