Two examples typical of paper-based devices will be introduced in this article. Paper is a material with a high Young’s modulus that vibrates sensitively due to environmental noise, voice, and sound. This study aims to create a triboelectric power generator to convert sonic vibration energy into electrical energy. A triboelectrically charged polytetrafluoroethylene sheet and a back electrode were attached to a paperboard. Another paperboard with a counter electrode attached was vibrated in the out of-plane direction. The generated power between the two electrodes reached 11.8 μW at 2 MΩ load. Water containing excessive amounts of Cu2+ is extremely harmful to human health and the biology of other animals. The other study developed a user-friendly, low-cost, sensitive, and ion-species-selective paper-based sensor to inspect drinking and industrial water for excessive Cu2+ levels. The paper-based sensor was fabricated simply by printing a quinone derivative dye solution onto a filter paper. The color of the dye on the sensor changed from yellow to purple in presence of Cu2+ as low as 2 ppm. Quantitatively, linear relationships were observed between the surface fluorescence intensity and Cu2+ concentration in the water samples.
