Magnetochromic Photonic Hydrogel for an Alternating Magnetic Field‐Responsive Color Display

Abstract As an external stimulus for stimuli‐responsive chromic materials, a magnetic field has the benefits of contactless control, instant action, and ease of integration into electronic devices. Hence, the development of a magnetically responsive photonic crystal provides a new platform for color displays. However, magnetically controlled display systems have been primarily limited to liquid systems of colloidal crystals; their application to solid chromic systems has been difficult because the ordered array structure is fixed by a polymer network. A novel solid magnetochromic photonic hydrogel is developed that enables colorimetric responses to an alternating magnetic field (AMF). This notable magnetochromic performance is attributed to the superior magnetothermal effect of 1D aggregates of magnetic chains fixed in a thermosensitive hydrogel. The AMF‐responsive magnetic hydrogel exhibits excellent stability for repeated use. This study presents a basis for the development of responsive solid materials with new optical effects for future chromatic applications.