A wearable, self-powered cardiac sensor capable of stable operation when being flexed is reported in a study published in this week’s Nature.

Self-powered, flexible electronics that can be worn on the skin could open up a new generation of biomedical devices to track various physiological signals, such as heartbeats. There is a need, however, to develop methods of energizing these technologies that does not rely on rigid power sources or wire connectors. While devices run off of flexible solar power cells have been realized in idealized, static settings, existing setups have proved unable to deliver a consistent power supply when subjected to the kind of flexing that would need to be endured when worn on an individual’s moving skin.

Takao Someya and colleagues present a thin, ultra-flexible, solar-powered device capable of measuring biometric signals accurately. The device is made up of an organic solar cell and an electrochemical transistor sensor, embedded onto a one-micrometre-thick bendable surface. By moulding a nanoscale grating pattern into the solar cells to increase light absorption, the authors were able to achieve high power conversion efficiency. They demonstrate their device operating as a cardiac sensor both on human skin and on the surface of a rat’s heart.

The authors conclude that this system could provide a template for developing various other types of self-powered flexible electronics.