A Dual Spiral-Coils Tactile Sensor with Novel Driving Modes for Inductive Force and Capacitive Proximity Sensing

This paper presents a tactile sensor by adopting the dual spiral-coils design to realize a novel tactile sensor with force/proximity sensing capabilities based on the TSMC 0.18 μm 1P6M standard CMOS process. The key features of the tactile sensor are as follows: (1) Two-ends routing on spiral-coil: to provide magnetic flux for force sensing; (2) Single-end routing on spiral-coil: to generate electric fringing field for proximity sensing. Thus, the dual spiral-coils design could reduce the footprint and achieve the force/proximity co-axial detections using inductive/capacitive sensing to avoid signal crosstalk. Force sensing measurements depict the sensitivity for one spiral-coil sensing is 6.7 nH/N, while two spiral-coils sensing can enhance 26.7 nH/N (near 4-fold, leveraging mutual inductance effect). Proximity sensing results indicate the maximum detected distance is about 5 mm. The capability of continuous tactile force/proximity sensing is also demonstrated.