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In a remarkable advancement, scientists from Shandong University, alongside colleagues from the Lanzhou Institute of Chemical Physics at the Chinese Academy of Sciences, have engineered an innovative elastic material capable of emitting ultraviolet (UV) light when subjected to mechanical stress—be it stretching, friction, or bending. This pioneering discovery could herald the advent of self-powered technologies that eliminate the need for batteries, wires, and external power sources, paving the way for applications as diverse as wearable sensors, robotic ‘smart skin’, and self-sterilising surfaces.
According to Global Energy, an energy focused online publication, at the core of this groundbreaking material is the inorganic phosphor Sr₃(BO₃)₂—strontium bromate infused with praseodymium ions. Researchers expertly dispersed these microparticles within an elastic polymer matrix made of polydimethylsiloxane. The success of this material hinges on forming a robust interfacial contact between the phosphor crystals and the polymer. It is within this interface that contact electrification occurs during mechanical deformation, resulting in a transfer of electrons that creates a local electric field. This field, in turn, excites the praseodymium ions, leading to the emission of distinctive ultraviolet light.
Experimental results reveal that the composite emits intense UV radiation with a peak wavelength of 272 nanometres, a range classified as solar-blind ultraviolet. This makes the emitted light easily detectable even under bright external lighting conditions, significantly distinguishing it from typical sources of UV light that can be masked by sunlight. During testing, the initial tensile cycle yielded a radiant power density of approximately 6.2 milliwatts per square metre, and remarkably, the material maintained detectable luminescence even after 10,000 cycles of strain, demonstrating its impressive stability.
One of the most exciting attributes of this new material is its self-healing capability. When the applied load is removed, the interfacial bonds partially regenerate on their own. After just one second of rest, the ultraviolet luminescence intensity can return to roughly 43% of its original output; this figure climbs to around 90% after 24 hours. However, researchers note an important balance: while moderate strains of up to 40% achieve optimal brightness and durability, excessive stretching can accelerate degradation of the interface, impairing the material’s longevity.
The scientists are currently exploring several practical applications for their revolutionary material. Possibilities include autonomous mechanical load sensors, flexible coatings for sensors, and intelligent skin elements for robotics. The self-powered nature is particularly advantageous for monitoring stress distribution without the complexity of electronic systems. The solar-blind characteristic also opens new avenues for stealthy optical marking and tracking of outdoor objects.
In an impressive demonstration, the researchers affixed an elastic film to a bird model’s wing; upon flapping, the film emitted a steady glow under ultraviolet light, effectively functioning as a self-powered optical tag—detectable even in bright conditions.
Another domain of interest hinges on the bactericidal properties of hard ultraviolet light. Experimental observations have shown that the radiation generated by stretching the film can eradicate harmful bacteria, including E. coli and staphylococcus, leading to applications in self-cleaning surfaces for everyday items such as door handles and medical instruments, which could function as self-sterilising tools during use.
Currently, this promising work is still in the research phase. To transition from laboratory concepts to practical engineering applications, researchers plan to conduct further experiments aimed at optimising interface properties, enhancing mechanical durability, and more accurately quantifying the relationship between load and UV output power.
