A Soft Mechanoluminescent Skin for High-Resolution Optical Tactile Sensing in Human-Machine Interaction

As soft interfaces become central to robotics, wearables, and human-machine interaction, a persistent challenge is to sense touch with high fidelity while keeping devices simple, robust, and negligible power requirement at the sensitive element. Herein, we report a soft mechanoluminescent (ML) tactile sensor converting force directly into light for imaging-based readout, integrating a thin, three-layer ML-skin with a CMOS module. Under mechanical stimulation, BaTiO₃ inclusions intensify local piezoelectric fields to excite ZnS:Cu emitters, producing light without electrical bias, pixel wiring, or external illumination. This optical transduction provides intrinsic electrical isolation while enabling scalable, high-density spatial mapping, where resolution is defined by optics rather than electrode routing. Coupled to a 640 × 480, 30 Hz CMOS array, the ML-sensor achieves a sensitivity of 27.5 N^-1, a 30 ms response time, ∼80 µm spatial resolution, and stable operation for over 8000 cycles. Furthermore, ML-sensor enables real-time handwriting recognition and human-machine interaction, demonstrating its potential as a natural tactile interface. By merging force-to-light conversion with a minimal device stack and vision-native readout, this work outlines a pathway to energy-efficient, conformal touch interfaces scalable across next-generation soft electronics and interactive systems.