Simulation of piezoresistance and deformation behavior of a flexible 3D printed sensor considering the nonlinear mechanical behavior of materials

In this research, the design, simulation, and 3D printing of flexible conductive sensors with the piezoresistive property were presented. The sandwich geometry, in which the conductive channels were placed in a flexible polymer matrix, was used to design the sensors. To print the sensors and achieve a compromise between the sensitivity and flexibility, the grid pattern with 60% infill density has been used. The sensors were printed from the filaments of thermoplastic polyurethane (TPU) and acrylonitrile butadiene styrene (ABS) with carbon black elements. To take into account the finite deformation of the constitutes, the hyperelastic and the hyper-viscoelastic models were assumed for ABS and TPU, respectively. The material parameters of ABS and TPU were obtained from the tensile and relaxation tests to consider the nonlinear and time-dependent behavior of materials. The printed sensors were wired to a known resistor and signals resulting from the deformation were monitored by the Arduino microcontroller. The electrical outputs of the sensors, including electrical resistance, relative resistance, and gauge factor of each sensor were found from simulations and compared with the experimental results. The simulation results showed that the 4 channels sensor represents a more uniform strain during bending. Moreover, it was observed that the electrical sensitivity increases with increasing the number of conductive channels and decreasing the width of them. The electrical results of the sensors showed that the gauge factor of the four channels sensor is in the range of 2–3 for the strain range of 0–0.2.