“Liquid fingerprinting” technique identifies unknown liquids instantly

“Validere translates this technology to create inexpensive, one-time-use test kits that can be used anywhere in the field to visually identify unknown liquids, all without the need for a dedicated power source,” said Ian Burgess, co-founder, CEO and CTO at Validere, who co-invented W-INK as a doctoral student at SEAS and technology development fellow at the Wyss Institute.

“Many people focus on making hardware smaller, but miniaturization often turns out to be the easy part,” Burgess said. “What’s difficult, and what our solution does, is to simplify the readouts to a level that you don’t need a technician to interpret the results. Anyone in the field can immediately know, on the spot, how to respond to a sampled liquid.”

Harvard’s Physical Sciences and Engineering Accelerator provided seed funding that enabled Aizenberg’s group to advance the technology from the lab to the pilot scale and attract further investment. The research group continues to refine W-INK to expand its range of applications.

Following a set of original publications describing W-INK technology in the Journal of the American Chemical Society, ACS Nano, and Lab on a Chip, in January 2016, Aizenberg, Lončar and Burgess reported improvements that make possible a colorimetric test for determining the volatility of liquids. This capability, described in a paper published in Scientific Reports, is of particular interest to the Department of Transportation. The ability to rapidly profile the volatility of crude oil, which is commonly transported by railroad, means decisions about proper transport containers can be made at the point of extraction in the field, helping to prevent accidental explosions. DOT is also supporting development of test kits for analyzing hazardous spills.

Harvard notes that Aizenberg’s lab specializes in reverse-engineering nature. W-INK mimics two biological systems to achieve a tunable device with properties that allow it to change colors when it comes in contact with certain liquids. The wings of some species of butterfly owe their brilliant colors to structure rather than pigment; the surface of each wing contains networks of tiny pores, the size of which determines the perceived color. Meanwhile, brittle stars, relatives of starfish, can change color from black to white by modulating the position of pigmented cells inside lens-like, light-focusing structures arranged in an array across the star’s back. 

By combining both of these mechanisms so that they respond optically to liquid infiltration into chemically modified porous structures, Aizenberg’s team developed a liquid decoder that is small enough to fit in the palm of the hand and can function without a power source. Engineered surface properties interact with liquids to change the interfacial chemistry of the test strip, which instantly causes corresponding color changes or markers to appear.

With support from the U.S. Federal Railroad Administration, Aizenberg is now leading research efforts to optimize the sensing capabilities, while Burgess is spearheading Validere’s development of software and an interface device that will translate visual test results into recommended action for handling identified liquids. The device will pair with disposable strips to comprise customizable field test kits that can be tailored to identify virtually any liquid or liquid mixture.

“The goal is to remove the element of human error from the identification and categorization of unknown liquids,” Burgess said.