Design and Manufacture of Flexible Epidermal NFC Device for Electrochemical Sensing of Sweat

Flexible and epidermal sensing devices are becoming vital to enable precision medicine and telemonitoring systems. The NFC (Near Field Communication) protocol is also becoming increasingly important for this application since it is embedded in most smartphones that can be used as pervasive and low-cost readers. Furthermore, the responder can be passive and can harvest enough power to perform electromagnetic sensing. Finally, the NFC coils are robust to bending and to the human body's presence. This contribution details the design of a new flexible device, including an electrochemical sensor communicating through the NFC protocol. A spiral NFC antenna is designed, and a manufactured prototype is experimentally tested to quantify the robustness to the inter-wearer variability and the bending. Lastly, the sensory data retrieval is validated by comparison with a portable potentiostat. The realized sensor can be comfortably worn and be easily read by smartphones independently from the wearer and from the point of application and could be used in future for estimating the user's psycho-physical health by analyzing the body's sweat.