Hair-Like Mechanoluminescent Structures with Ultralow Activation Threshold for Dynamic Force Sensing

Mechanoluminescence (ML)-based sensing technology opens up new opportunities for photonic/electronic skin due to their self-powered nature, visible spatial mapping of mechanical stimuli, and intrinsic responses to dynamic forces. However, challenges such as weak brightness and high activation threshold have hindered their development. Inspired by hair-like structures of human skin, skin-bionic mechanoluminescent PDMS/ZnS:Cu microcilia array film (MLMCA) is fabricated using a magnetic field-assisted template method. The MLMCA exhibits tunable aspect ratios and ML intensity, with the underlying relationship between microcilia structure and ML performance clarified through finite element analysis. The MLMCA achieves an ultralow activation threshold at the micronewton level (≈10 mN) owing to the stress concentration induced by high aspect ratio. With excellent sensitivity to dynamic mechanical stimuli, the MLMCA enables texture recognition with an accuracy of 99.95% when integrated with the image machine learning approach. Furthermore, an ML-based Braille-to-speech translation system is developed and achieved a high recognition accuracy of 96.74%. This study not only tackles the persistent limitation of high activation thresholds in ML-based sensing but also pioneers the practical use of ML-based tactile sensing in texture discrimination and Braille reading.