Self-Healing Negative Photochromic Hydrogel for Rewritable Display

To address the growing demand for energy-efficient information storage and smart displays, we have developed a fast, self-healing, rewritable photochromic hydrogel based on visible light-responsive reverse photochromism. The developed hydrogel is engineered by integrating carboxyl-functionalized spiropyran into a poly(vinyl alcohol) (PVA) matrix, utilizing hydrogen bonding, crystallization of PVA chains, and B–O bonds. The reverse photochromic effect is significantly enhanced by the addition of sodium tetraborate, which is further augmented by the temperature increase. Additionally, a carboxyl-functionalized spirooxazine is used as a couple for UV tuning stimulation, so the self-healing reverse photochromic hydrogel could respond to both the visible and UV, impacting more diverse color variations as well as enhancing the controllability of the hydrogel. This approach promotes the development of reverse photochromic hydrogels, potentially expanding their applications in tunable and rewritable display technologies.