Ultra-flexible and high-sensitive triboelectric nanogenerator as electronic skin for self-powered human physiological signal monitoring

Electronic skin (E-skin) with tactile sensing characteristics has presented great potential in disease diagnosis and health assessment; however, the imperfect combination of ultra-flexibility and high-sensitivity have restricted its widespread application. Here, we report a contact-separation triboelectric-nanogenerator (CS-TENG) consisting of ultra-flexible micro-frustum-array polydimethylsiloxane (mf-PDMS) film and Cu electrodes as the basic friction units, which can achieve self-powered weak physiological signal monitoring with great comfort. The CS-TENG uses elastic mf-PDMS as both the major body and the friction layer to realize ultra-flexible and conformal contact with irregular human skin. By exploring the microelectromechanical system (MEMS) preparation process, a uniform and controllable mf-arrays structure was fabricated to utilize both the normal and shear stresses, thereby increasing friction and enhancing device sensitivity. The CS-TENG displays high sensitivity (5.67 V/105Pa), good linearity (R2 = 0.99 of voltage), high stability (more than 80000 cycles), and fast response time (60 ms). With these outstanding characteristics, the CS-TENG can sense subtle changes in wrist pulse under various physiological conditions, which can also be easily arranged into a 1 × 3 array to mimic the three-fingered pulse-taking in traditional Chinese medicine. This work provides a new way to prepare ultra-flexible and high-sensitive TENG as E-skin and demonstrates its potential application.