Transparent pressure sensor with high linearity over a wide pressure range for 3D touch screen applications

Abstract

Touch screens are used in various fields such as smart phones, Internet of things (IOT) and wearable electronics. Conventional pressure sensors used to recognize touches have nonlinear sensitivity, which makes it difficult to input various functions. In addition, present pressure sensors with linear sensitivity are not transparent, making it difficult to apply them in touch screens. To overcome these limitations, we developed pressure sensors with high transmittance and linear sensitivity. For attaining high transmittance, we use refractive index- matching technology to minimize light scattering on the micro-pyramid structure surface. And by designing a unique structure in which the linear conversion to pressure-electric signal takes place when a pressure sensor is under load, we attained linear sensitivity of the pressure sensors. These highly transparent pressure sensors have high transmittance (~85 %) and high linearity ($R^2>0.995$) in pressure range of 5 to 100 kPa. Developed pressure sensors are expected to enhance the usability of touch screens.