The touch sensor can detect the human touch by sensing the change of capacitance. Based on the touch IC TTP223-B, this module can detect a human finger in 0~3mm, that is, you can place this sensor under a non-metallic surface such as the glass or paper, with a thickness less than 3MM, this would be useful for applications that waterproof is needed, or you want to make the buttons secret.
With the panel mount design, that is, the side of the touchpad is smooth, Elecrow Crowtail- Touch Sensor is easy to install in projects, and users can easily install it onto cases or other internal materials.