Wearable Janus nanofiber membrane-based colorimetric sensors for directional transfer and analysis of sweat

Wearable sweat sensors are promising for real-time personalized health monitoring in a noninvasive manner. However, how to improve the wearing comfort and accuracy affected by sweat accumulation and unstable assay regent immobilization still remains challenges. Herein, we proposed a wearable colorimetric sensor for in situ and simultaneous monitoring of glucose, Ca2+ and Zn2+ in sweat by using Janus nanofiber membranes as a matrix. The sensor was prepared by an electrospinning method and patterned by a direct writing technique. The Janus nanofiber membrane allowed sweat directionally transport across the membrane in an irreversible way, thus effectively avoiding sweat retention on skin surface and keeping skin dry. To achieve uniform distribution and stable immobilization of detection regents, the reagents were in situ encapsulated into the nanofibers during electrospinning, which was beneficial for enhancing the accuracy and stability of the sensor. The obtained wearable device demonstrated excellent sensing performances in view of sensitivity, specificity, stability and accuracy. Human studies conveyed that the sensor possessed the ability for glucose, Ca2+ and Zn2+ monitoring in actual samples comparable to commercial assay kits.