Development of graphene-based flexible nanocomposite sensors operating in the dynamic strain range for wearable devices

The aim of this thesis is to develop a strain sensor capable of responding to two different strains in the same region or operating within the dynamic range. To achieve this, a resistive pattern was created on the two-layer sensor surfaces using graphene and thermoplastic polyurethane. Detailed electrical characterizations of inks containing different resistive nanofillers under dynamic voltage were completed. To determine the ratios of resistive filler material to thermoplastic polyurethane inks used in the two layers, we first carried out a single-layer sensor fabrication. We then analyzed the response time, measurement factor, linear operating range, and hysteresis of these sensors. The analyses revealed the responses of the sensors at high and low concentration values in the single-layer sensor design. A two-layer sensor was designed based on these reactions, capable of simultaneously measuring two different values in the same area. The sensor uses a matrix with low graphene nanomaterial concentration (25% GNP/TPU ratio) on one surface and high concentration (60% GNP/TPU and 70% GNP/TPU ratios) on the other surface. The responses of the sensors were characterized. A sensor has been developed within the scope of this thesis that can respond to strain with different resolutions and works sensitively at low strains. The measurement factor values of these sensors range from 32.96 to 41.54 for 1-10% strain and 7.85-4.95 for 10-50% strain.