Background: Sweat, as an easily accessible bodily fluid, is enriched with a lot of physiological and health information. A portable and wearable sweat sensor is an important device for an on-body health monitoring. However, there are only few such devices to monitor sweat. Based on the fact that sweat is mainly composed of moisture and salt which is much more abundant than other trace ions in sweat, a new route is proposed to realize wearable sweat sensors using CdSSe nanowire-chips coated with a polyimide (PI) membrane.
Results: Firstly, the composition-graded CdS1-xSex (x = 0-1) nanowire-chip based sensor shows good photo-sensitivity and stress sensitivity which induces linear humidity dependent conductivity. This indicates good moisture response with a maximum responsivity (dI/I) 244% at 80% relative humidity (RH) even in the dark. Furthermore, the linear current decrease with salt increase illustrates the chip sensor has a good salt-sensing ability with the best salt dependent responsivity of 80%, which guarantees the high prediction accuracy in sweat sensing. The sensor current is further proven to nonlinearly correlate to the amount of sweat with excellent stability, reproducibility and recoverability. The wearable sweat sensor is finally applied on-body real-time sweat analysis, showing good consistence with the body status during indoor exercise.
Conclusions: These results suggest that this CdSSe nanowire-chip based PI-coated integrated sensor, combined with inorganic and organic functional layers, provides a simple and reliable method to build up diverse portable and wearable devices for the applications on healthcare and athletic status.
Keywords: CdSSe nanowire chip; Humidity sensing; Salt sensing; Sweat monitoring; Wearable sweat sensor.