Figure 3. Wearable PENG-based cardiovascular sensors.

A. Peapod-inspired hierarchical PENG. (i) Conceptual illustration of the piezoelectric ZnSnO₃-SMC-P(VDF-TrFE) NFs. (ii) Schematic illustration of the piezoelectric device configuration. (iii) Schematic illustration of the electrospinning process used to prepare the P(VDF-TrFE)-based NFs. (iv) The device attached on the wrist. (v) Real-time output waveforms produced by the piezoelectric device when attached to the wrist. Reproduced with permission [85]. Copyright 2022, Elsevier Ltd. B. Ultrathin epidermal piezoelectric sensor. (i) Schematic illustration of the fabrication process of a self-powered pressure sensor. (ii) Radial artery pulse signals detected by the self-powered pulse sensor. Reproduced with permission [87]. Copyright 2017, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. C. Self-powered 2D-material sensor. (i) Photo and optical microscope image of the SnSe piezoelectric device. (ii) Output voltage signal of a typical SnSe nanogenerator. (iii) Heart rate detection by attaching the SnSe nanogenerator on the chest of the tester. Reproduced with permission [90]. Copyright 2020, Royal Society of Chemistry.