Chemochromic Damage-Detecting and Recovery System Using Affordable Hydrogel.

A multipurpose chemochromic protector is proposed with a hydrogel made from a mixture of sodium chloride, starch, and water, and the deposition of a copper layer on the nylon polyethylene film surrounding the hydrogel. This hydrogel is found to be chemically stable, water-retaining, shock-absorbent, biocompatible, cost-effective, and highly reactive with copper enough to realize its chemochromic characteristics. The varying chemical compositions of the hydrogel show that the presence of poly(acrylic acid) (PAA) inside can enhance the damage-detecting and recovery capabilities of the protector. The compressive strength measurement reveals that the hydrogel becomes effectively solidified with the formation of copper chloride and the evaporation of water molecules to cover the damaged areas. In the shear strength experiment, the PAA-included hydrogel is proven to have the high adhesiveness necessary for the recovery of the protector. The damage-detecting and recovery experiment successfully presents the copper-specific chemochromic properties of the protector, implying that the addition of PAA intensifies the color changes of the hydrogel as well as its increased stiffness in the damaged areas. The chemochromically operating surface protector with a simple fabrication process, intuitive measurement, and an alternative working mechanism would be able to promote related studies and contribute to the development of additional protective measures such as for diverse protective clothing, miscellaneous robotic structures, and numerous space applications.