The ability to produce distributed sensors by tailoring materials readily available on the market is becoming an emerging strategy for Internet of Things applications. Embedding sensors into functional substrates allows one to reduce costs and improve integration and gives unique functionalities inaccessible to silicon or other conventional materials used in microelectronics. In this paper, we demonstrate the functionalization of a commercial polyurethane (PU) foam with the conductive polymer PEDOT:PSS: the resulting material is a modified all-polymeric foam where the internal network of pores is uniformly coated with a continuous layer of PEDOT:PSS acting as a mechanical transducer. When an external force causes a modification of the foam microstructure, the conductivity of the device varies accordingly, enabling the conversion of a mechanical pressure into an electric signal. The sensor provides a nearly linear response when stimulated by an external pressure in the range between 0.1 and 20 kPa. Frequency-dependent measurements show a useful frequency range up to 20 Hz. A simple micromechanical model has been proposed to predict the device performance based on the characteristics of the system, including geometrical constrains, the microstructure of the polymeric foam, and its elastic modulus. By taking advantage of the simulation output, a flexible shoe in sole prototype has been developed by embedding eight pressure sensors into a commercial PU foam. The proposed device may provide critical information to medical teams, such as the real-time bodyweight distribution and a detailed representation of the walking dynamic.

At the present, no wearable device is available to continuously monitor the ulcer status. For chronic or infected wounds, the literature reports a pH interval between 6.5 and 9. This study aims to produce an innovative scaffold capable of monitoring ulcers healing. The scaffold constituted by a synthetic biocompatible material, poly(ether)urethane-polydimethylsiloxane (PU-PDMS), was manufactured by spray, phase-inversion technique. A micro-fibrillar tubular scaffold was obtained using a 2% polymer solution and H2O as non-solvent (I layer) and 0.2% and H2O (II layer) and was lyophilized. Morphological analysis of PU-PDMS scaffold surfaces was performed using a stereo-microscope after Sudan Black B staining. The biocompatible scaffold was functionalized by inkjet-printing of a biocompatible conductive polymer (PEDOT:PSS), used as active material in a biosensor, to develop organic electrochemical transistor (OECT) architecture. This polymer presents a high sensitivity to positive ions in liquid environment and allows to determine ions concentration in easy and stable way. The fiber textile electrochemical device was prepared by inkjet-printing process and connected with electric contacts to create a channel and a gate electrode to control the modulation changes of the sensor. The device functionality was proved on human serum at different pH (between 4 and 10). The morphological analysis showed a dense, non-porous surface obtained with the 2% solution, while a porous surface was obtained with the 0.2% solution where the PEDOT:PSS was positioned. This feature was maintained after lyophilization and re-hydratation. The characteristic of the device was tested showing the sensitivity to saline concentration and the effective functionality of the device. Moreover, the device response shows a dependence to pH variations and also transconductance presents substantial changes in presence of pH variation. These data suggest the possibility of using this sensorised scaffold as a wearable detector for wound healing monitoring in patients affected by chronic lesions.

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