Mechano-responsive luminescence, or mechanochromic luminescence (MCL), is a type of luminescence that can be reversibly controlled by the addition of mechanical stimuli. Organic materials exhibiting MCL have been an ongoing area of development since the early 2000s, and the number of reports into such materials has been steadily increasing. While the majority of MCL systems rely on the brittle nature of organic crystalline solids, there is a growing interest in "flexible" organic crystals that exhibit mechanical bending or shape deformation owing to their elasticity/plasticity. Such non-destructive deformed crystals may exhibit a new type of MCL that can be controlled by the magnitude of the force stress. In this review, we describe MCL systems capable of the spontaneous recovery of changes in their luminescent properties in response to the loading/unloading of mechanical stress. We particularly focus on the MCL of flexible crystals based on the density gradient of molecular packing (i.e., elastic and plastic crystals) and an emerging system known as "superelastochromism,” which is based on spontaneously reversible crystal polymorphism. This emerging research area has the potential to play an important role in the promotion of next-generation soft crystals.

机械响应发光或机械致变色发光 (MCL) 是一种可以通过添加机械刺激进行可逆控制的发光。自 2000 年代初以来，展示 MCL 的有机材料一直是一个持续发展的领域，关于此类材料的报告数量一直在稳步增加。虽然大多数 MCL 系统依赖于有机结晶固体的脆性，但由于其弹性/塑性而表现出机械弯曲或形状变形的“柔性”有机晶体越来越受到关注。这种非破坏性变形晶体可能表现出一种新型的MCL，可以通过力应力的大小来控制。在本次审查中，我们描述了能够响应机械应力的加载/卸载而自发恢复其发光特性变化的 MCL 系统。我们特别关注基于分子堆积密度梯度的柔性晶体（即弹性和塑性晶体）的 MCL，以及基于自发可逆晶体多晶型的新兴系统“超弹致变色”。这个新兴的研究领域有有望在下一代软晶体的推广中发挥重要作用。”这是基于自发可逆晶体多晶型。这一新兴研究领域有可能在推动下一代软晶体方面发挥重要作用。”这是基于自发可逆晶体多晶型。这一新兴研究领域有可能在推动下一代软晶体方面发挥重要作用。