SkinAid: A Wirelessly Powered Smart Dressing Solution for Continuous Wound-Tracking Using Textile-Based Frequency Modulation

In this article, SkinAid, a battery-free, low-cost, robust, and user-friendly smart bandage for electrochemical monitoring and sensing of chronic wounds is proposed. The working principle of the bandage is based on direct frequency modulation of a tri-electrode electrochemical sensing of wound data. The electronics and biotelemetry links were realized using low-cost manufacturing process of textile embroidery onto fabric substrate. The transmitter was represented by a bedsheet with novel corrugated crossed-dipole made of Elektrisola-7 embroidered onto gauze fabric. An input RF signal of 1 W was transmitted at 462 MHz from the bedsheet to the all-textile bandage featuring a rectifying circuit, a voltage-controlled oscillator (VCO), an electrochemical sensor, and a 915-MHz dipole for re-transmission of the modulated wound data. We demonstrate that for wound fluid emulated by various uric acid concentrations from 0.2 mM to 1.2 mM, corresponding modulated frequency varies from 1090 MHz to 1145 MHz for signals captured at 25 cm away from the bandage. For pH modulation ranging from 2 to 10, the corresponding modulated frequency was between 800 MHz and 830 MHz for signals received at more than 6 feet away from the bandage. For quick and reliable assessment, two empirical models were developed for the direct frequency modulation as a function of uric acid and pH. To the best of our knowledge, this is the first time an all-textile (fabric-integrated), battery-free and wirelessly powered smart bandage have been proposed for wound monitoring. This result can be used as a first step in developing RFID-type, battery-free, and low-cost 5G/6G smart bandages using millimeterwave and terahertz frequencies where the bedsheet can be host to a MIMO-aided beamforming.