A variety of mechanoluminescent (ML) materials have recently reinvigorated studies of luminescence activated by mechanical stress, but few practical applications have been demonstrated due to the destructive nature of the process. To overcome these shortcomings, elastico-mechanoluminescent (elastico-ML) materials, which generate luminescence under elastic deformation, have been suggested with a view to their use in practical devices. However, the weak brightness and limited white colour expression of these materials must be resolved before they can be employed in practical applications. Here, we report a wind-driven ML device that produces significant brightness and emits warm/neutral/cool white light over a range of colour temperatures from zinc sulphide (ZnS) microscopic particles embedded in a polydimethylsiloxane (PDMS) composite. Harnessing wind-activated mechanoluminescent devices in practical displays or lighting systems could pave the way to new environmentally friendly lights, which reduce energy waste and promote sustainability. Broader context Mechanically driven light generation is an exciting and under-exploited phenomenon with a variety of possible practical applications. Mechanoluminescence (ML) has potential applications in colourful displays and white-light sources driven by vibrating mechanical actions. However, the related research has suffered from the difficulty in obtaining a strong, repeatable signal, so enhancing ML intensity has not been a major area of focus. Weak brightness and limited white colour expression of ML must be resolved with a view to its use in practical ML displays or ML light sources. Here we report a new wind-driven ML device that produces signicant brightness and emits light over a range of tunable white colours. A patterned, colourful ML driven by wind was also demonstrated. Harnessing wind-driven ML in practical lighting systems could pave the way to new environmentally friendly lights based on wind motion, to cut down energy waste and promote sustainability.

wileyonlinelibrary.comtechnologies because ML can be generated by all mechanical vibrations occurring in nature. [ 3 ] Elastico-ML, luminescence by elastic deformation, has been mainly used for advanced applications because of its potential durability. [ 4,5 ] Various approaches have been proposed for using ML in sensor applications, mainly for visualizing crack propagation and for stress distribution. [5][6][7][8][9][10] Recently, the polydimethylsiloxane (PDMS)-supported zinc sulfi de (ZnS) composite structure has received considerable attention [ 3,[11][12][13][14][15][16][17] because of its durable [ 15,16 ] and color-tunable [ 3,17 ] ML characteristics. Such PDMS composites are very attractive owing to their easy fabrication, mechanical robustness, and low cost. Notably, from the viewpoint of application, the various color expression technologies could broaden the MLapplication fi elds. To date, many papers have been published reporting various inorganic compounds with color of ultraviolet, [ 18 ] blue, [ 19,20 ] green, [ 21,22 ] orange, [ 23 ] and red. [24][25][26] Alternative methods for ML color-tuning have also been proposed; the tuning characteristics were obtained by mixing different colored ML particles [ 17 ] or by changing the dopant concentration. [ 27 ] However, the strategies of previous reports have focused on color-tuning of ML material itself through newly developed inorganic ML compounds. In this paper, we introduce a new strategy for the color manipulation of ML by fl uorescent dyes physically combined with existing ML materials.Color conversion using wavelength-converter materials has been widely applied in light-emitting devices such as organic/ inorganic light-emitting diodes [28][29][30] and dye lasers. [31][32][33] Several types of wavelength-converter materials are available, such as phosphors, semiconductors, and dyes. [ 28 ] In particular, organic fl uorescent dyes are promising for the development of low-temperature solution-processed devices because organic dyes are usually soluble in various solvents. Hence, if energy-transferrable organic fl uorescent dyes with different luminescence and absorption spectra can be combined with ML materials, broad-color manipulation technology would be promoted because various emission colors can be produced depending on the dyes selected.Color conversion, long-wavelength light emission by absorbing shortwavelength light, is an attractive approach for developing a broad-color expression technology and is widely used in solid-state lighting, dye-lasers, and colorful displays. Up to now, many papers have been published reporting various mechanoluminescent materials emitting color of ultraviolet, blue, green, orange, and red. However, the strategies of previous reports have focused on color-tuning of mechanoluminescent material itself through newly developing inorganic mechanoluminescent compounds. Here, a new strategy for the color manipulation of mechanoluminescence (ML) is introduced by physically combining fl uorescent dyes with existing mechanol...

No abstract

No abstract

No abstract