Flexible wireless skin impedance sensing system for wound healing assessment

Monitoring the wound condition is important for wound treatment. In this paper, we develop a flexible wireless electronic system for in-situ and real-time monitoring the bio-impedance of wounded skin. The system is composed of an 5933 CE high-precision impedance converter, a CC2541 Bluetooth microcontroller with meandering copper wires and star-shape electrodes deposited on flexible polymer substrate by using magnetron sputtering in vacuum. Both in vitro experiments on a normal pork skin and in vivo experiments in the process of chronic wound healing on a living pig were conducted for system evaluation. Data are transmitted via Bluetooth to a smartphone for monitoring and analysis. The system has very good flexibility with a maximum strain of 31.6%. Results show that the system has excellent accuracy and repeatability for impedance measurements. It is also reliable as it is able to reveal the relation between the measured impedance and the electrodes distance, wound types, and location of skin layers. The condition of a wound can be readily distinguished by its bio-impedance. The system could be readily, yet with some minor modifications, applied to monitor chronic wound healing for human being.