Modeling Sliding Friction Between Human Finger and Touchscreen Under Electroadhesion

When an alternating voltage is applied to the conductive layer of a capacitive touchscreen, an oscillating electroadhesive force (also known as electrovibration) is generated between the human finger and its surface in the normal direction. This electroadhesive force causes an increase in friction between the sliding finger and the touchscreen. Although the practical implementation of this technology is quite straightforward, the physics behind voltage-induced electroadhesion and the resulting contact interactions between human finger and the touchscreen are still under investigation. In this article, we first present the results of our experimental study conducted with a custom-made tribometer to investigate the effect of input voltage on the tangential forces acting on the finger due to electroadhesion during sliding. We then support our experimental results with a contact mechanics model developed for estimating voltage-induced frictional forces between human finger and a touchscreen as a function of the applied normal force. The unknown parameters of the model were estimated via optimization by minimizing the error between the measured tangential forces and the ones generated by the model. The estimated model parameters show a good agreement with the ones reported in the literature.