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“Watermark Ink” device wins 2013 R&D 100 Award

Thu, 07/11/2013 - 11:25am

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A device that can instantly identify unknown liquids based on their surface tension has been selected to receive the 2013 R&D 100 Award—known as “the Oscar of Innovation”—from R&D Magazine.

Invented by a team of materials scientists and applied physicists at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard, the “Watermark Ink” (W-INK) device offers a cheap, fast and portable way to perform quality control tests and detect liquid contaminants.

W-INK fits in the palm of a hand and requires no power source. It exploits the chemical and optical properties of precisely nanostructured materials to distinguish liquids by their surface tension.

Joanna Aizenberg, Amy Smith Berylson Prof. of Materials Science at Harvard SEAS and a Core Faculty member of the Wyss Institute for Biologically Inspired Engineering, says she envisions a broad range of industrial and consumer applications—for example, detecting toxins in a chemical spill; testing alcohol levels or the quality of gasoline, sugar or caffeine; or the creation of simple teaching sets and toys.

The project was a collaboration between Aizenberg and Marko Lončar, Tiantsai Lin Prof. of Electrical Engineering at SEAS.

This is the second time in a row that Aizenberg’s team has won an R&D 100 Award. In 2012, her research group was recognized for their invention of an extremely low-friction material called SLIPS, for “slippery, liquid-infused porous surfaces.” Inspired by the pitcher plant, SLIPS resists liquid, ice and dirt and could be incorporated into a wide range of products, from medical devices to refrigerators.

The W-INK concept relies on a precisely fabricated material called an inverse opal, a layered glass structure with an internal network of ordered, interconnected air pores. Akin to the litmus paper used in chemistry labs around the world to detect the pH of a liquid, the W-INK device changes color when it encounters a liquid with a particular surface tension. 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.

Selectively treating parts of the inverse opal with vaporized chemicals and oxygen plasma creates variations in the reactive properties of the pores and channels, allowing one liquid to pass through while excluding others. When the correct liquid enters a pore, the chip reflects light differently, producing a telltale change in color.

Source: Harvard Univ.

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