Development of a monitoring smart patch device to assess wounds healing process through Bio-Electrical Impedance Analysis (BIA).

The skin has sophisticated ways of healing quickly and efficiently. Nevertheless, certain individuals' cellular responses can compromise the healing process itself, hindering or slowing it down. Failure to heal wounds - either partially or completely - is often linked to elderly age or certain diseases, such as diabetes. These factors are among the main contributors to the development of chronic wounds, i.e., wounds that, despite having been treated adequately, show little or no sign of healing, resulting in abnormal scar formation and an increased susceptibility to infection. These wounds affect millions of people worldwide and many of these remain refractory to current treatments, representing a major socio-economic burden. The current therapeutic landscape includes a variety of approaches, such as clinical dressings, skin grafts, antibiotics and surgical methods but, despite intensive research, the management of chronic wounds remains an unmet medical challenge. Moreover, wound monitoring is often entrusted exclusively to periodic inspections by a doctor. Therefore, the development of improved and innovative strategies for healing and monitoring skin wounds holds great importance in the healthcare landscape. The thesis project is part of a broader research involving the collaboration of the Haute école d'ingénierie et d'architecture de Fribourg (HEIA-FR) and Harvard Medical School on the design of a personalised, multi-functional and patient-tailored smart patch with the aim of promoting the healing of chronic wounds through electrical stimulation and monitoring the process through skin impedance measurement. The thesis aims to develop the wound monitoring part of this research project through Bio-Electrical Impedance Analysis (BIA). BIA technique can be widely exploited for point-of-care diagnostic devices and, as an electrical measurement, it is completely non-invasive and can be carried out by portable, fast-response, inexpensive and safe equipment. The project concerns the realisation of a Proof of Concept for a stand-alone, Bluetooth Low Energy (BLE) connected measurement device, composed by an Electrical Impedance Measurement System, an ARM-based microcontroller and multi-point connector for ad-hoc designed, flexible electrodes array. The final system can perform an electrical impedance mapping over up to 32 points for a precise spatial resolution wound analysis, with a reduced measurement to transmission time latency for a continuous wound monitoring. Tests on the correct functioning of the device were conducted on porcine skin samples. Burn wounds and stab wounds were procured and the ability of the smart patch to map impedance distribution was analysed. Electrical impedance mapping showed high precision in determining wound size and location. The system overall performances may be tuned after wound size and required resolution by properly controlling the electrode size and position.