CMOS-MEMS Tri-Axial Piezo-Resistive Tactile Sensor with Monolithically/Vertically Integrated Inductive Proximity Sensor

This study demonstrates a novel tri-axial piezo-resistive tactile sensor vertically integrated with a inductive proximity sensor using standard CMOS process (Fig. 1). Normal and shear loads sensing capabilities are achieved by measuring the signal changes of four piezo-resistive cross beams. The proposed sensor design has three merits: (1) the tri-axial tactile sensing unit and the proximity sensing unit can be vertically integrated on one chip, (2) normal and shear loads can be detected by four discrete piezo-resistive sensing elements, (3) the footprint of the chip can be reduced due to the vertical integration of sensing elements. The measurements demonstrate the capabilities of tactile sensing for both normal and shear loads and proximity sensing. The testing results indicate that the proposed tri-axial piezo-resistive tactile sensor shows the normal load (Z-axis) sensitivity of 0.55 mV/N, the X-axis shear load sensitivity of 1.3 mV/N, and the Y-axis shear load sensitivity of 0.76 mV/N.