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

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Mechanoluminescent (ML) foams offer real-time optical monitoring of human motion for energy, sensing, and safety.
• Conventional polymer-based ML composites exhibit inefficient stress transmission in thick structures, leading to surface-confined emission and weak global luminescence.

Purpose of the Study:

• To enhance the mechanoluminescent performance of foams for improved force dispersion and global luminescence.
• To investigate the dual structural and electrical roles of aluminum oxide (Al2O3) as an additive in ML foams.
• To demonstrate the application of modified ML foams in smart footwear for dynamic loading detection.

Main Methods:

• Incorporation of Al2O3 as a dual-function additive (structural and electrical) during ML foam fabrication.
• Utilizing surface-adsorbed species on Al2O3 to induce spontaneous bubble formation and create a porous architecture.
• Leveraging the triboelectric properties of Al2O3 to strengthen the interfacial triboelectric field and enhance ML particle emission.

Main Results:

• Al2O3 addition created a sponge-like porous structure, enhancing force dispersion and global mechanoluminescence.
• The positive triboelectricity of Al2O3 improved the interfacial field, resulting in bright emission even at low ML particle loading.
• Application in shoe soles demonstrated full-area signal monitoring and spatially resolved detection of dynamic loading during human motion.

Conclusions:

• Al2O3 acts as a dual-enhancement additive, improving both the structure and electrical properties of ML foams.
• The developed ML foams show significant potential for practical self-luminous platforms in smart footwear, healthcare monitoring, and wearable stress sensing.
• This approach offers a pathway to overcome limitations of conventional ML composites for real-world applications.