Development of a Robust and Flexible Wearable Sensor Derived from Disulfide-Linked Polyurethane/Graphene Nanoplatelets with Enhanced Temperature Tolerance

This work presents a novel method to synthesize polyurethane (PU) with a disulfide linkage and embed graphene nanoplatelet (GnP) to form composite films for wearable strain sensors. These films are highly sensitive and flexible. The PU was chain-extended with a disulfide chain extender, which improved molecular flexibility. This modification provided greater flexibility in comparison to traditional butanediol-extended PU. The chemical structure of the samples was qualitatively analyzed utilizing FTIR spectroscopy. Purity of GnP was characterized using Raman spectroscopy. The shape and structure of the nanocomposite were analyzed by using scanning electron microscopy (SEM), which showed the distribution of GnP in the PU matrix. Atomic force microscopy (AFM) was used to analyze the three-dimensional arrangement of GnP in the polymer. Graphite coating was applied to improve the conductive network within the material. Electromechanical testing was performed by using an in-house Arduino-controlled linear actuator. The results showed a higher gauge factor and better sensitivity than typical commercial sensors. This novel approach combines the properties of polyurethane with disulfide linkages and the strong electrical conductivity of GnP. As a result of its enhanced performance, it showed an excellent result for the monitoring of human health, and it could also be used in wearable devices and personalized healthcare. In addition, thermal analysis was carried out to determine the thermal degradation and stability of both the hard segment and the soft segment. The glass transition temperature was determined by using differential scanning calorimetry (DSC) analysis. This wearable sensor exhibits excellent temperature tolerance, ensuring reliable operation under extreme conditions.