Mechanics designs-performance relationships in epidermal triboelectric nanogenerators

Mechanics designs in wearable skin-integrated electronics, also known as epidermal electronics, play an important role in the device performance ranging from flexibility, to robusticity, and to the overall electrical performance. Compared with conventional wearable electronics, self-powered electronics that converting mechanical energy to electricity by using the activities from body's daily motions offers advantages of simple device structures and battery-free characteristics. Here we study a class of mechanics designs that associate with effective working area for stretchable epidermal triboelectric nanogenerators (e-TENGs), and report the relationships between effective working area and the electrical performance of e-TENGs. With the advanced cobweb-serpentine pattern mechanics design, a simple structured, low-cost single-electrode mode e-TENG with open-circuit voltage of -60 V and a short circuit current output of -20 mu A was achieved. Moreover, the e-TENG's performance is very stable under a broad range of strain values from 0% to 30%. The report of mechanics designs-performance relationships shows a trade-off behavior between the stretchability and the effective working area, which significantly enhances our understanding of mechanics designs for e-TENGs.