Dual-Functional Alumina Additive Enabling Efficient, Volumetric Mechanoluminescence for Nighttime Safety Footwear

초록

Visualizing mechanical force distribution through mechanoluminescent foams allows real-time optical monitoring of human motion for energy, sensing, and safety applications. However, conventional polymer-based mechanoluminescent composites often suffer from inefficient stress transmission in thick structures due to their high elasticity, resulting in surface-confined emission and weak luminescence in the global regions. In this study, Al2O3 is introduced as a simple additive that performs dual functional roles in both structural and electrical aspects. During fabrication, surface-adsorbed species on Al2O3, such as oxygen and moisture, induce spontaneous bubble formation, generating a sponge-like porous architecture that enhances force dispersion and consequently improves mechanoluminescent performance in the global region of the foam. Moreover, the intrinsically strong positive triboelectricity of Al2O3 strengthened the interfacial triboelectric field, leading to highly bright emission even with a low loading ratio of ML particles. When applied to shoe soles, the foam enables not only full-area signal monitoring but also spatially resolved detection of dynamic loading during human motion. This study reveals the dual structural and triboelectric enhancements induced by a simple additive and highlights its potential for realizing practical self-luminous platforms in smart footwear, healthcare monitoring, and wearable stress sensing.

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