3D-Stacked Thin-Film Transistors for Simultaneous Detection of Pressure and Temperature

Deformable sensors can be conformally attached to a curvilinear surface, so they can detect stimuli successfully. They have been widely investigated in electronic-skin applications such as soft robots and prostheses. Due to emerging nanotechnology and materials science, various deformable sensors have recently been developed. Fabrication of sensors using thin-film transistors (TFTs) is one of the primary development trends. The sensors have shown some advantages such as improvement in sensitivity and minimal crosstalk. However, the TFTs are affected by temperature <i>T</i>, which causes a <i>T</i>-responsiveness of the sensor which is intended to detect some stimulus, not <i>T</i>. To detect an accurate stimulus regardless of <i>T</i>, the <i>T</i> influence must be calibrated. Although a multi-functional sensor with <i>T</i> calibration was proposed, their calibration methods required <i>T</i> sensors that used poly(vinylidene fluoride-co-trifluoroethylene). To utilize the calibration method widely, a more-general <i>T</i> sensor must be used for the calibration method. In this study, we demonstrate a multi-functional sensor that can detect pressure <i>P</i> and <i>T</i> synchronously. The multi-functional sensor is composed of a <i>T</i> sensor and a <i>P</i> sensor. A <i>T</i> sensor is fabricated using organic thin-film transistors (OTFTs). On the <i>T</i> sensor, a <i>P</i> sensor is fabricated using OTFTs and a piezo-resistive sheet. The <i>T</i> sensor is influenced by only a change of <i>T</i>, whereas the <i>P</i> sensor is influenced by a change of both <i>P</i> and <i>T</i>. To produce accurate <i>P</i> information regardless of <i>T</i>, the current value of the <i>P</i> sensor is calibrated using the <i>T</i> value produced from the <i>T</i> sensor. Finally, the multi-functional sensor is attached to a robotic gripper and the gripper with the sensor successfully holds and lifts a hot cup.