Measurement Calibration of Flexible Piezoresistive Sensors Based on Strain Transfer Model Accounting for Coating Effect

The assumption of zero strain at both ends of the sensing layer for flexible sensors results in inaccurate strain transfer assessment because of the traction from the coating to the sensing layer. This article proposed a new strain transfer model considering the coating effect to accurately characterize the actual strain of the sensing layer. First, a five-layered strain transfer model is established based on shear lag theory, and the strain functions for the sensing layer and coating are conducted to react with the actual boundary conditions. Next, the strain transfer coefficient of the coating effect is derived by solving the functions with the consideration of continuity conditions at the ends of the sensing layer. Results of numerical simulations and experiments demonstrate that the proposed model predicts a more accurate strain compared with the existing model, and the increase in coating length will reduce the strain transfer loss in the flexible sensor. This allows for the calibration of the measured strain from flexible sensors based on the strain transfer coefficient.