Personalized real-time health monitoring in non-clinical environments can significantly improve the life quality by regularly evaluating health status, immediate warning of abnormality, and remote diagnosis. The continuous detection of various vital signals such as respiration, perspiration, and temperature have been realized by wearable sensors. Heart rate is another critical parameter which is closely related to cardiovascular health. Cardiovascular disease is one of the leading causes of death globally, which costs more than $219 billion each year in healthcare service, medicine, and loss of productivity. The precise continuous monitoring of pulse waveform is critical for assessing overall cardiovascular health and the state of the autonomic nervous system (ANS) responsible for regulating cardiac activity.

The emerging frontiers in real-time cardiovascular health monitoring demand that the corresponding sensors be biocompatible, wearable, and self-sustainable. The capability of sensor systems to efficiently scavenge the stray, weak environmental energies through sustainable pathways would enable self-powered bioelectronic systems. Triboelectric nanogenerators (TENG) can effectively transform the otherwise wasted environmental, mechanical energy into electrical power. Recent advances in TENGs witness a significant boost in the output performance. However, obstacles hindering the development of efficient triboelectric devices based on biocompatible materials continue to prevail. Being naturally degradable, biocompatible, low-cost, and lacking in cytotoxicity, chitosan and polyvinyl alcohol (PVA) are two materials with great potential being functional constituents in biomedical devices.

Here, we present for the first time the holistic engineering of chitosan and PVA with tunable mechanical properties, biodegradable rates, and electrical outputs for wearable TENGs, through revealing and understanding the interactions between the constituent materials and the structure-property-performance relations.[1, 2] The feasibility of laser processing of biopolymers was explored for the first time to improve the TENG performances. Leveraging the high mechanical deformability and biocompatibility of the constituent materials, the optimized triboelectric devices built with PVA composite films and chitosan composite films exhibit stable and robust triboelectricity outputs. Such wearable devices are capable of detecting the imperceptible degree of skin deformation induced by human pulse and capture the cardiovascular information encoded in the pulse signals with high fidelity for self-powered cardiovascular health monitoring. The gained fundamental understanding and demonstrated capabilities are expected to enable the rational design and holistic engineering of novel materials for more capable biocompatible triboelectric devices that can continuously monitor vital physiological signals for self-powered health diagnostic and therapeutic systems.

[1] R. Wang, S. Gao, Z. Yang, Y. Li, W. Chen, B. Wu and W. Wu, Adv. Mater. 2018, 30, 1706267.
[2] R. Wang, L. Mu, Y. Bao, H. Lin, T. Ji, Y. Shi, J. Zhu and W. Wu, Adv. Mater. 2020, 32, 2002878.