All Paper-Based, Multilayered, Inkjet-Printed Tactile Sensor in Wide Pressure Detection Range with High Sensitivity

Paper has attracted considerable interest as a promising pressure-sensing element owing to its foldability/bendability and deformability due to its high porosity. However, paper-based tactile sensors reported hitherto cannot achieve high sensitivity and a wide sensing range simultaneously. In this study, a resistive tactile sensor using carbon nanotube- and silver nanoparticle-printed mulberry paper as a pressure-sensing element and electrodes, respectively, is developed. The rough surface and high inner porosity of mulberry paper induce a significant change in the contact area when a multilayer-stacked structure is used, resulting in increased sensitivity to pressure. Moreover, the enhanced mechanical robustness of mulberry paper originating from the highly bonded network of long and thick fibers affords a wide pressure-sensing range. The sensor exhibits a high sensitivity exceeding 1 kPa⁻¹ in an applied pressure range of 0.05–900 kPa; this achievement has not been reported among paper-based tactile sensors. Furthermore, the sensor exhibits a fast response/relaxation time, low detection limit, high resolution, high durability, and high flexibility. The advantages of the sensor afford several applications, including a crosstalk-free pressure sensor array, a three-axis pressure sensor, and wearable devices for measuring signals from a user.