Paper-Based Capacitive Touchpad Using Home Inkjet Printer

In this paper, an inkjet-printed paper-based capacitive touchpad is proposed. This touchpad detects finger contact by sensing the change in effective capacitance caused by the skin electrical impedance. A low-cost flexible disposable touchpad with nine capacitive buttons is fabricated, using paper as a substrate. The use of home inkjet printing technology with silver nanoparticle ink makes the fabrication process simple, fast, cheap, and environmentally friendly. The performance of the proposed touchpad is measured with a microcontroller, and tests are conducted for both the cases of finger and touch pen operation. The measured capacitance of the non-touched state is 228-236 pF, whereas the measured capacitance of the touched state is 340-564 pF. The differences in the capacitance of each state are sufficiently large to indicate that a finger has made contact with the touchpad. The sensitivity of the proposed sensor is evaluated, and the parameters of the proposed sensor are compared with those of other paper-based touch pads.