Recent progress of nanogenerators acting as biomedical sensors in vivo

Since the nanogenerator (NG) was invented in 2006, it has been successfully developed and utilized to harvest various forms of mechanical energy in vivo. The NGs promote the progress of self-powered biomedical devices. Moreover, NGs can also be used as sensors to detect a variety of important physiological signals, which brings us closer to real-time, high-fidelity monitoring of physical and pathological information. This paper summarizes the in vivo applications of NGs as biomedical sensors, including in cardiac sensors, respiration sensors, blood pressure sensors, gastrointestinal sensors and bladder sensors. However, there are still many challenges in using NGs as sensors in vivo. For example, how can we minimize and encapsulate the NGs, how can we increase the stability and reliability during long-term detection, and how can we establish a corresponding relationship between the NG's electrical output and the physiological signals. It is also critical to follow the medical principles more closely in the development of self-powered sensors in the future. We believe that the self-powered sensors would promote the development of the next-generation healthcare monitoring systems. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.