A label that reveals an image when breathed on could have anti-counterfeit applications, according to the researchers behind the concept.
A team at the University of Michigan led by chemical engineer Nicholas Kotov are developing the nanomaterial alongside scientists in South Korea and say it could have uses including protecting medicines from counterfeiting.
The material is are deposited on nanostructured sheets of plastic, and stand proud - rather like pillars - according to U-M doctoral student Terry Shyu. The moisture in breath condenses on these nanopillars and creates a contrast with the surrounding area of the film to reveal the hidden image, she adds.
Holographic labels are widely used in the retail and banking sectors but are "very easy to counterfeit," according to Kotov, who notes that the structures can be either overt or covert and are applied using inkjet printer technology - but are much harder than holographic labels to replicate because they require more sophisticated tools.
The printer used to create the image templates has to be able to print the tiny droplets of ultraviolet-cured polymers - roughly 500 times smaller than the width of a human hair - that are needed to mould the nanopillar arrangements. The material used to make the pillars is a blend of polyurethane and an adhesive.
Once the template is made, however, labels can be printed in large rolls at a cost of roughly one dollar per square inch, which should make it a viable option for brand protection and anti-counterfeit applications.
The nanopillars can be printed onto a range of substrates, including fabric, paper, and metals, according to the team.
U-M says it is pursuing patent protection for the intellectual property and is also seeking commercialization partners to help bring the technology to market.
The work is published in the journal Advanced Materials.