Differential water-wetting behaviour used for anti-counterfeiting measureDate: 05 January 2020 Tags: Nanotechnology
Researchers at the Indian Institute of Technology (IIT) Guwahati have developed a new approach to anti-counterfeiting measures.
Researchers have developed a smart interface embedded with two different water wettabilities, extremely water repelling (superhydrophobic) and extremely water loving (superhydrophilic), which can hide information or make it visible under certain definite conditions.
Adding a layer of complexity, the researchers used a molecular printer to imprint a pattern of micron size that will become visible only when dipped in water or when moist air is blown.
The coating is not only hydrophobic but is also reactive. Taking advantage of the reactive surface of the coating, the researchers used a chemical (glucamine) to write letters on the coated surface.
The glucamine-treated region becomes selectively and extremely water-loving (superhydrophilic) and hence becomes visible to the naked eyes when dipped in water or when moist air is blown.
Since the rest of the hydrophobic region of the coated surface is still chemically reactive, they modified it using another chemical (octadecylamine) to make the surface chemically inert.
The pattern which is highly water-loving allows water to get in thus allowing light to pass through without much scattering. This makes the pattern visible when it is wet.
The rest of the region is highly water-repelling so there is trapped air that scatters light and hence remains opaque.
The team found the patterned coating to be physically durable even when exposed to a very high (100 degree C) and very low temperature (10 degree C).