Self‐Assembled Wavy Optical Microfiber for Stretchable Wearable Sensor

Abstract Smart wearable devices have made remarkable success in medical‐grade human vital signal monitoring and have promoted the realization of precision medicine and telemedicine. The flexibility and stretchability are significant for wearable devices, which determine the adhesion to the skin and influence the signal accuracy. Here, a stretchable and ultrathin optical sensor based on a self‐assembled wavy microfiber is proposed. Thanks to the “bottom–up” strategy, the wave structure of the microfiber can be adjusted artificially, paving the way for the design of stretchable optical devices. Due to the microbend loss of the microfiber, the optical sensor has a sensitivity of ≈257 per unit strain and a good repetition (the standard deviation is 1.7% over 100 cycles). With the great sensor performance, the wrist pulse with a high signal‐to‐noise ratio is detected and the blood pressure is monitored successfully via the pulse arrival time, showing a potential application for human health monitoring.