A three-dimensional rate-dependent cohesive zone model with electrical damage for soft conductive adhesive interface

The patch-type biomedical sensor attached to human skin by a soft conductive adhesive layer has a good application potential in human healthcare. However, the complex strain of human skin can cause damage to the adhesive interface which can lead to signal drift and affect the long-term service reliability of the sensors. It is imperative to predict the trend of interfacial damage and signal drift and develop compensation method to enhance the sensor service reliability. In this work, a three-dimensional cohesive zone model (CZM) coupled with electrical damage was proposed to simulate the interfacial damage and signal drift behavior of sensor electrode with soft conductive adhesive layer. The viscoelastic behavior of the soft interface was described by the Wiechert model, and electrical damage behavior was incorporated into the CZM. The different electrical damage evolution mechanisms for normal and tangential loading were introduced based on experiments. The model was tested by tensile-shear tests with various normal and tangential loading combinations, and the effectiveness of the CZM in characterizing the mechanical and electrical damage behavior of soft conductive interface in complex loading conditions was verified. Then, the model was employed to predict the signal drift of the sensor electrode in cyclic torsional loading. The simulation results are in good agreement with the experiments. This work provides a numerical strategy for predicting the electrical signal drift of sensor electrodes under complex loading cycles.