Development of a touch sensor capable of touch and touch load recognition

Abstract

A capacitive-type touch sensor for detecting the touch position and touch load, simultaneously, is designed and manufactured using transparent electrode material. Generally, a touch sensor senses only the touch position. However, as the touch sensor proposed in this study is designed by separating the touch position and touch load sensing parts, it is possible to recognize the touch load, in addition to the touch position. The touch sensor is mainly composed of a polyethyleneterephthalate (PET) film substrate coated by an indium tin oxide (ITO), an ITO glass substrate, and a transparent elastomer. The ITO, as the transparent electrode, has an approximately 86% light transmittance and a sheet resistance of 30Ω/square, and is patterned by photo-lithography process. A transparent elastomer, for load recognition, is sandwiched between the two transparent substrates and senses the magnitude of the touch load by detecting the change in capacitance value due to the change in the distance between the upper and lower electrodes, generated by the touch load. The fabricated touch sensor is 183mm in width and 234mm in length with a 10in. touch area. It has 32 transmit lines for signal driving, 47 receive lines for signal detection, and two channels of ground lines. It can detect multi-touch with more than 10 points and sense loads up to 700gf, simultaneously.