A bio-inspired proximity-tactile sensor array with beyond-extreme detection depth for embodied intelligence

Flexible proximity-tactile sensors have attracted significant attention for enhancing robotic perception. Among them, capacitive flexible proximity-tactile dual-mode sensor arrays are rapidly becoming a key solution. However, existing sensor arrays are limited by their physical configurations and electrical interconnects, making it difficult to achieve high resolution and large detection depth simultaneously. To overcome the limited detection depth of traditional capacitive sensor arrays, this work introduces a novel tri-mode architecture with a distance-sensing mode, extending the maximum detection depth by up to 104.56% compared to a single sensor unit. Inspired by near-pupil reflection, a pupil-like layer was integrated into the traditional dual-mode sensor to realize high-resolution and tunable detection depth simultaneously. By introducing a fractal electrode design to enhance the fringing field, the sensitivity of proximity and tactile sensing is significantly improved. Additionally, sacrificial template methods are used to fabricate microporous structures in the electrodes and dielectric layers, enabling high sensitivity (3.38 × 10^-2 pF·kPa^-1) over a broad pressure range (0 - 22.7 kPa), a wide detection limit (0 - 400 kPa), and large capacitance variation (>2.8 pF). The sensor array achieves high resolution and tunable detection depth (24.36 - 49.83 mm) and a large sensing distance (>90 mm). By stacking the proposed sensor array, the sweeping robot and humanoid robot demonstrate multi-level safety perception, obstacle recognition, gesture detection, and proximal target localization. This work addresses the fundamental trade-off between resolution and detection depth in capacitive flexible dual-mode proximity-tactile sensors, advancing robotic perception and interaction capabilities and paving a broad pathway for the practical deployment of future multi-mode sensors.