Asymmetric and Ultrasensitive Structural Color Response in Nanochain‐Embedded Photonic Composites

Abstract Mechanochromic photonic crystals, capable of altering structural colors in response to external forces, are emerging intelligent materials in various fields, such as visual sensors and anti‐counterfeiting technologies. However, conventional mechanical responses of photonic crystals mainly rely on stretching or compression, resulting in symmetric and limited mechanochromic effects due to restricted changes in lattice spacing, particularly limiting the recognition of the direction of force. Here, asymmetric and ultrasensitive structural color responses are reported in colloidal photonic composites featuring embedded one‐dimensional (1D) photonic nanochains of colloidal particles based on shear‐induced lattice orientation change. It is shown that shearing deformation tilts the photonic nanochains within the polymer matrix, leading to a remarkable and asymmetric color shift depending on shear force and observing directions. The asymmetric response encourages to develop ultrasensitive twist sensors capable of detecting subtle twisting movements as low as 0.2° and twist direction. Furthermore, by integrating magnetic and deformation orientation control, dynamic optical anti‐counterfeiting labels capable of displaying highly intricate patterns are devised. This unique shear‐induced color‐shifting mechanism expands the responsiveness of mechanochromic materials, with broad implications in many other areas, including structural health monitoring, soft robotics, and artificial skin.