Mechanochromic Materials: From Principles, Multi‐Mode Integration, to Emerging Applications

Mechanochromic materials, which dynamically alter their optical properties in response to mechanical stimuli, represent a versatile platform of smart materials. This review comprehensively overviews recent advances in mechanochromic systems, focusing on two primary mechanisms: structural color modulation and emission color changes. Structural color modulation, often based on reflection, represents the more common approach, while emission color changes, though highly sensitive, constitute a significant complementary strategy. Materials are classified by their different responses to applied strains, including in-plane (stretch/compression), out-of-plane (grinding/shear), and multiaxial (bending) strains. This review also analyzes multi-stimuli integration with thermochromic, chemochromic, and photochromic functionalities for enhanced versatility. Applications are analyzed, including sensing, displays, anti-counterfeiting, smart windows, and bioinspired artificial skins, with significant highlights in dual-signal photonic-ionic skins and mechanoelectrical sensors. Finally, the opinions are shared on challenges in scalability, environmental stability, spectral tunability, and real-world implementation, as well as the future directions emphasizing biohybrid systems, artificial intelligence-driven design, and scalable manufacturing. This review systematically summarizes the progress in mechanochromic materials, which will promote future fundamental research, functionalization, as well as the advancement toward practical applications.