CMOS-MEMS Tactile Sensor with Adjustable-Sensitivity Force Sensing and Proximity Detection

This work, for the first time, presents an adjustable-sensitivity inductive force sensor, realized through an interdigitated spiral structure extending from existing design. The interdigitated spiral structure is implemented using the TSMC$0.18 \mu \mathrm{m}$1P6M standard CMOS process. The design employs one spiral for inductive force sensing, while the other is voltage-driven to modulate sensitivity and power, enabling the device to adapt its operating conditions to different applications. Furthermore, the interdigitated spiral structure enables sensitivity adjustment without sacrificing sensing range, while retaining the previously demonstrated capacitive proximity sensing capability. Within a 2 N force measurement range, with one spiral fixed at$0.5 \mathrm{V}_{\text{pp}}$, varying the driving voltage of the other spiral from$0 \mathrm{V}_{\text{pp}}$to$1 \mathrm{V}_{\text{pp}}$modulates the force sensitivity (power consumption) from$52.6 \mu \mathrm{V} / \mathrm{N}(64.6 \mu \mathrm{W})$to$133.9 \mu \mathrm{V} / \mathrm{N}(258.4 \mu \mathrm{W})$. Proximity sensing is also demonstrated with a sensitivity of$0.90 \text{fF} / \text{mm}$within a 2.5 mm sensing range.