‘Self-Healing’ Thermochromic Ink

While thermochromic ink is often used as an anticounterfeiting tool for applications such as tax stamps, many security printing and brand protection firms consider the ink to provide a weaker level of protection compared to more advanced technologies, in large part because it is widely available to any printer.

The ink can also suffer from a lack of durability in that the thermochromic micro-capsules carried in the ink may degrade under UV light, or as a result of abrasion, chemical exposure or repeated use.

However, these durability problems may now have been resolved by researchers from multiple Saudi Arabian universities and the Egyptian Petroleum Research Institute. They have developed a thermochromic ink based on ‘self-healing’ hydrogels, with enhanced resistance to physical and mechanical damage, and a longer shelf-life.

The key ingredient of this ink is a natural dye (anthocyanin) extracted from butterfly pea flowers, which is known for its strong colour and high heat resistance. The dye is embedded inside the hydrogels – which consist of a soft, flexible material made mostly of water and a polymer network.