Wireless Textile Moisture and pH Sensor for Wound Care

One of the main problems of hard-to-heal wounds regards the monitoring of their healing progress. Currently, clinicians monitor the wound’s status by removing the dressing, disturbing the healing process. A relevant parameter that they need to monitor is wound moisture. Indeed, a low amount of exudate can desiccate the wound, while a high level of moisture will lead to maceration. Thus, to optimize the healing process, it is particularly important to maintain an optimum level of moisture, while limiting unnecessary dressing changes. An innovative solution to address this issue is the design of a bandage with an integrated moisture sensor. In this work, we developed a textile sensor based on a conductive polymer poly(3,4- thylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) that discriminates wound’s moisture level. PEDOT:PSS is screen printed on a gauze in a various geometries. Exploiting its intrinsic electrochemical properties, the sensor operates in real time by monitoring impedance variations that span over several orders of magnitude between dry and wet states. The here presented sensor allows to combine different commercial textile substrates, which are regularly used for wound care, to design and implement an advanced “smart” wound dressing able to continuously monitor in real time the moisture condition of the wound. Tunable properties and performance can be obtained, depending on the type of textile layers used, targeting different wound types and exudate levels. The possibility to connect the smart textile patch to a RFID or to a NFC interface leads to implementing an integrated fully passive smart bandage for rapid, low-cost, disposable and wireless real-time monitoring of wound moisture levels.<br/> <br/>While a slightly acidic pH provides optimum healing conditions to control collagen formation, increase fibroblasts activity, and hamper bacteria proliferation, more alkaline pH values (7−9) are typical of hard-to-heal wounds.10−13 Although pH sensing is a consolidated analytical practice and a variety of potentiometric probes are available in the market, commercial devices might be hardly adapted to wound healing monitoring, taking into account safety and conformability requirements. An additional technical challenge regards the small sample volume and its complex composition. To address these challenges, we have developed a novel textile two-terminal sensor for pH monitoring based on IrOx particles embedded in a PEDOT:PSS thin film and an absorbent layer ensuring the delivery of a continuous wound exudate flow across the sensor area. This pH sensor exhibits a reversible response with a sensitivity of (59 ± 4) μA pH−1 in the medically relevant pH range for wound monitoring (pH 6−9), and its performance is not substantially affected either by the presence of the most common chemical interferents or by temperature gradients from 22 to 40 °C. Thanks to the robust sensing mechanism based on potentiometric transduction and the simple device geometry, the fully assembled smart bandage was successfully validated in flow analysis using synthetic wound exudate.