Highly sensitive flexible strain and temperature sensors using solution processed graphene palladium nanocomposite

•This work reports an optimized composition of the reduced graphene oxide(rGO) and Palladium (Pd) nanoparticles.•The rGO and rGO-Pd nanocomposites were synthesized using chemical routes.•The flexible strain and temperature sensors were fabricated on PDMS/Kapton substrates with screen-printing technology.•The strain sensor exhibited an outstanding performance for various tensile strains.•The loadcell designed with these sensors demonstrated high sensitivity and resolution.•We have also reported flexible temperature sensors exhibiting positive and negative temperature coefficient behaviors [Display omitted] This work reports highly sensitive, flexible, and fast response strain sensors for load cell application and a temperature sensor with a tunable temperature coefficient of resistance (TCR). The proposed sensors are fabricated with solution-processed reduced graphene oxide (rGO) and Palladium (Pd) nanocomposite. The strain sensor is encapsulated with a Polydimethylsiloxane (PDMS) substrate to ensure flexibility and moisture protection. The strain sensor's performance was studied; the gauge factor was calculated as ~22 to ~198 in the strain range of 0.05–0.625%. The sensor exhibited high durability beyond 1000 cycles, fast response (~39 ms). A binocular type of load cell was designed and simulated using COMSOL Multiphysics software to study the strain profiles under applied load conditions. The designed load cell was tested with a micro universal test machine (UTM) for different loads. Its response was stable, linear, and repeatable with a sensitivity of 23.52 mV/V/Kg and a resolution of 0.0085 Kg/mV at an excitation of 5 V. Additionally, the nanocomposite was investigated for temperature response with different ratios of rGO-Pd and tuned the TCR of the sensor. The temperature sensor displayed good sensitivity and linearity with both negative temperature coefficient (NTC) and positive temperature coefficient (PTC) depending on rGO and Pd nanoparticles (NPs) composition.