Shear-Force Sensor With Point-Symmetric Electrodes Driven by LTPS TFT Active Matrix Backplane

Abstract

In this study, we successfully demonstrated a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$700 ~\mu \text{m}$ </tex-math></inline-formula> thick shear-force sensor with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60\times60$ </tex-math></inline-formula> high resolution array by introducing a combination of an originally developed pressure-sensing elastomer and a newly proposed taxel (tactile pixel) structure with four point-symmetric electrodes. When shear forces are applied to the sensor substrate in several directions by lifting a weight, four sets of resistances between the electrodes are read through low-temperature polycrystalline-silicon (LTPS) thin-film transistors (TFTs) in each taxel and clear outputs corresponding to that direction can be confirmed. Furthermore, as a result of evaluating the object recognition performance of the tactile sensor by using jigs with engraved small dimples, it was confirmed that the recognized minimum size of the shape was 1.5 mm, which suggests that the spatial resolution of this sensor is superior to the human hand perception ability. Because this sensor is ultra-thin, not bulky, and potentially applicable to flexible substrates, it is quite promising as a sensor that can be mounted on the fingertip of a robot hand with multiple functions.