Temperature and moisture are critical factors for both the environment and living creatures. Most temperature sensors and humidity sensors are rigid. It still remains an unsolved problem to fabricate a flexible sensor that can easily detect temperature and humidity at the same time. In this work, we made a flexible multifunctional temperature and humidity sensor from graphene woven fabrics. The integrated sensor could measure temperature and humidity simultaneously. The temperature-sensing part and the humidity-sensing part were stacked in layer structure, occupying little space and showing good flexibility while exhibiting high sensitivity and very little mutual interference. The different factors that affected the sensing properties of the sensor were examined. The integrated sensor was successfully utilized in several real life application scenarios, which showed its potential for wider use in environment sensing and health monitoring.

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A variety of autonomous oscillations in nature such as heartbeats and some biochemical reactions have been widely studied and utilized for applications in the fields of bioscience and engineering. Here, we report a unique phenomenon of moisture-induced electrical potential oscillations on polymers, poly([2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide-co-acrylic acid), during the diffusion of water molecules. Chemical reactions are modeled by kinetic simulations while system dynamic equations and the stability matrix are analyzed to show the chaotic nature of the system which oscillates with hidden attractors to induce the autonomous surface potential oscillation. Using 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 and achieved the continuous energy production for more than 15,000 seconds with an energy density of 16.8 mJ/cm2. A 2-Volts output voltage has been produced to power a liquid crystal display toward practical applications with five energy harvesters connected in series.

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