The portable device enabling cheap and fast quality control and liquid contamination checks has won the prestigious R&D 100 Award from the R&D Magazine.
Watermark Ink, invented in 2011 by a team from the Harvard School of Engineering and Applied Sciences (SEAS), uses chemical and optical properties of nanomaterials to distinguish liquids according to their surface tension. It requires no power source and comfortably fits into the palm of a hand.
"Visual colorimetric indicators, such as pH paper or pregnancy tests, have enjoyed wide commercial success because they are inexpensive and exceptionally easy to use,” says Joanna Aizenberg, a Professor of Materials Science at Harvard SEAS. “Our W-INK technology greatly expands upon this concept because it can detect any liquids through cleverly designed, chemically encoded opals that reveal easy-to-recognize, macroscopically distinct structural colour patterns.”
The inverse opal, forming the basis of the device, is a precisely fabricated layered glass structure with an internal network of ordered, interconnected air pores. Similarly to the litmus paper used in chemistry labs around the world to detect the pH of a liquid, the W-INK device changes colour when it encounters a liquid with a particular surface tension. Parts of the opal are treated selectively with vaporized chemicals and oxygen plasma creating variations in the properties of the pores and channels. This in turn allows only one liquid to pass through while excluding others. When the correct liquid enters a pore, the chip reflects light differently, producing a tell-tale change in colour.
“The W-INK technology draws on insights from chemistry, materials science, optics, self-assembly, and nanotechnology to create a deceptively simple chip with the potential to make a really big impact,” said Cherry A. Murray, Dean of Harvard SEAS.
A single chip can react differently to a wide range of substances; it is also sensitive enough to distinguish between two very closely related liquids. The device has already stirred interest of the industrial community and has found utilisation in a whole range of applications – in toxin detection in chemical spills, testing alcohol levels or the quality of gasoline, sugar or caffeine.
The Watermark Ink device became the 51 winner of the annual innovation Prize awarded by the editors of the R&D Magazine. It thus joint an elite group of ground-breaking technologies including the halogen lamp, the fax-machine, the liquid crystal display, the HDTV, or the Nicoderm anti-smoking patch, that have won the award in previous decades.