Mechanochromic photonic fibers composed of strain responsive colloidal crystals and spandex yarns

Mechanochromic photonic fibers can realize a visual dynamic color response to external stimuli, and are widely used in colorimetric sensing, smart display, and medical care. At present, colloidal crystals-based mechanochromic photonic fibers with a core-sheath structure have been successfully prepared by electrophoretic deposition and dip-coating. However, problems such as the complicated preparation process and the limited range of color change are still unsolved and hinder the applications of mechanochromic photonic fibers. Here, a mechanochromic photonic fiber with a wide color shift range is prepared by a simple and effective strategy. The fiber is fabricated by coating elastic rubber containing a non-close-packed array of silica particles onto spandex yarn. The obtained photonic fiber displays a structural color that can be controlled by adjusting the diameter and volume fraction of silica particles. Under stretching, the fiber shifts from red to blue with a color change range of 127 nm. More importantly, it achieves reversible color change in the visible range under mechanical strain. These mechanochromic photonic fibers based on colloidal crystals and spandex yarns are promising for smart wearables, display textiles, and visual sensors.