An active acoustic back cover based on piezoelectric elements

A trackpad is a pointing device, featuring a tactile sensor, able to translate the motion and position of a user's finger, or a stylus, to a relative position on the device screen. In this work, we analyze the possibility to use the back cover of tablets or smartphones as trackpad, capable of detecting the presence and position of a finger on their external surface. In order to convert the smart device back cover in a trackpad we glue on its inner surface, some small, thin piezoelectric plates. The proposed trackpad was analyzed by FEM in order to understand how many piezoelectric plates are needed and where they must be placed along the inner cover surface; the device resolution and sensitivity varying the finger position was also analyzed, confirming the device capabilities.