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A variety of autonomous oscillations in nature such as heartbeats and biochemical reactions have been widely studied and utilized for applications in the fields of bioscience and energy technology, etc. Here, we report a unique phenomenon of moisture-induced electrical potential oscillations on P(MEDSAH-co-AA) polymers during the diffusion of water molecules. Using the moisture in the ambient environment as the activation source, this self-excited chemoelectrical reaction could have broad influences and usages in surface-reaction based devices and systems. As a proof-of-concept demonstration, an energy harvester is constructed to demonstrate the continuous energy production for more than 15000 seconds with an energy density of 16.8 mJ/cm2. A 2-Volts output voltage has been produced to power a liquid crystal display (LCD) with five energy harvesters connected in series toward practical applications.

One grand challenge in haptic human-machine interface devices is to electromechanically stimulate sensations on human skins wirelessly by thin and soft patches under a low driving voltage. Here, we propose a soft haptics-feedback system using highly charged, polymeric electret films with the annulus-shape bump contact structure to induce mechanical sensations on volunteers under an applied voltage as low as 5 volts. Together with bendable lithium ion batteries and a flexible circuit board, an untethered stimulation patch is constructed for active operations of at least 2 hours with low power consumptions. As an application example, a “silent haptic communication” system is demonstrated to transmit English alphabet letters via the mechanical beating patterns from a patch onto the fingertip of a receiving volunteer. The analytical model, design principle, and performance characterizations can be applicable for the integrations with other devices in wearable electronics toward various applications, including AR (augmented reality) and VR (virtual reality).