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For Suslick, the nose knows

Beckman Institute researcher Kenneth Suslick is turning chemical vapors into visual data, giving the world new technology that could change the way everything from toxic chemicals to flavorful coffees are analyzed.

Published on April 30, 2010

Fittingly enough, Kenneth Suslick’s development of an electronic nose technology that can, among other things, “sniff out” different coffees based on their aromas, got its start in a restaurant.

Suslick, a member of the Beckman Institute’s Bioimaging Science and Technology group, has a research focus on olfaction and artificial olfaction, especially as it applies to the use of sensor arrays for chemical detection and analysis. His research group developed an “opto-electronic nose” based on a colorimetric sensor that has the ability, as reported in recent papers, to accurately distinguish among 20 different toxic chemical vapors and among 10 different varieties of coffee.

The technology’s lineage can be traced back about 10 years to a dinner conversation and restaurant placemats. During dinner, a prospective graduate student asked the professor what he would be doing if he joined Suslick’s group.  

“No professor ever wants to hear that question,” Suslick said. “The truth of the matter is we don’t really know what a new student’s thesis is going to end up being because that is going to develop.”

But the question stirred something that had been rolling around in Suslick’s head for awhile. 

“I sat down in the restaurant with him, grabbed the paper placemat, turned it over, and started scribbling,” Suslick said. “Basically his whole thesis project got written down in about a six minute period of time.”

That six minute genesis led to a research line that has resulted in 20 papers, a dozen patents and applications, national scientific and media attention, and a start-up company for the technology. The colorimetric sensor has shown a much higher degree of specificity and accuracy for detecting chemicals than other electronic nose technologies. Suslick’s group has also created a prototype that makes the technology user-friendly and hands-on: a handheld device that gives readouts of the data.

“I think it is a whole undeveloped arena for new technology,” Suslick said. “Human beings are visual creatures. But it’s interesting to think about what technologies we would have developed if we were derived from intelligent canines. Most animals live and die by their sense of smell not by their sense of vision. The ability to generate new technologies based on smell rather than vision is a relatively open area.”

And it’s an area that Suslick said is ripe for potential applications like the detection of toxins or for analyzing commercial products such as coffee or wine.

“Our whole approach to this technology has been to take advantage of the fact that digital imaging is incredibly inexpensive and incredibly high resolution in terms of quality data,” Suslick said. “Essentially we turn a smell into a visual picture.”

The electronic nose technology is just the latest success for Suslick, a Chicago native who has been a faculty member at Illinois since earning his Ph.D. from Stanford in 1978.  

Suslick is a Beckman original, joining the Institute when it opened in 1989. He is the Marvin T. Schmidt Professor of Chemistry and a Professor of Materials Science and Engineering at Illinois. He has won many prestigious awards in chemistry. Suslick was awarded the Sir George Stokes Medal from the Royal Society of Chemistry, the ACS Nobel Laureate Signature Award for Graduate Education, and the Materials Research Society Medal.

Suslick’s research involves inorganic and bio-organic chemistry, materials (both inorganic and biomaterials), and surface, analytical, organometallic, and physical chemistry.

Suslick said his research group is pretty evenly divided between work in the area of the chemical and physical effects of ultrasound, and work in the area of olfaction and artificial olfaction. The ultrasound group has efforts in two main areas: nanomaterials that are synthesized using sono-chemistry and understanding the conditions created during bubble collapse using sono luminescence, which is the light that comes out when the bubble collapses.

The work involving organometallic chemistry is focused on metalloporphyrins (biological compounds combined with a metal ion) and their application as chemical sensors.

“We spent many years working on heme proteins, synthetic analogs of heme proteins, metalloporphyrins,” Suslick said. “I was very interested in metals and biological systems and it turns out that the olfactory receptors are almost certainly metalloproteins.”

The work eventually blossomed into research involving olfaction, and then – following that dinner meeting with the prospective grad student, Neal Rakow, who became a key member of Suslick’s group – electronic nose technology.

 “My unconscious had been mulling this problem over for some time,” Suslick said of the project’s placemat origins. “The project originally involved using a number of different metalloporphyrins – these are metal-containing dye molecules.

“Mother Nature uses them for a variety of things. Hemoglobin has its red color due to a metalloporphyrin that contains iron. Chlorophyll contains a porphyrin-like molecule with magnesium in the center. These porphyrins are basically donuts and the metal ion fits in the middle, in the hole.”

Suslick’s idea was to put the metalloporphyrins in an array that could take advantage of the color changes that take place when they interact strongly with different chemicals.

“Mother Nature uses basically the same donut,” Suslick said. “But the color of these porphyrins depends very much on both the metal and what is bound to the metal above and below the donut.

“As an example arterial blood, which has oxygen bound to the iron, is a scarlet red, whereas venous blood, which is deoxygenated and doesn’t have an oxygen bound to the iron, is purplish. That is an example of exactly the kind of color change that we were interested in detecting. We figured that we could use a whole bunch of different metalloporphyrins as a way of differentiating one smell from another, one analyte in the gas phase from another analyte.”

The early work resulted in a paper on metalloporphyrin arrays in Nature by Suslick and Rakow. The research eventually led to the development of the first opto-electronic nose, a new technology that was able to distinguish between chemicals with a great degree of specificity. The opto-electronic nose consists of a printed array of different nanoporous pigments that strongly interact with chemicals in the gas phase, producing patterns of color changes.

The Suslick group’s colorimetric sensor is unaffected by humidity, allows for the visualization (through color change) of the pattern of the complex mixture of chemicals present in any odor or vapor, and has been shown to be effective for the general detection of industrial toxins. The handheld device features a white LED, a touchscreen, and the same camera found in cell phones.

When vapors were funneled into the prototype, causing an interaction with the sensor array, the device proved its worth when testing for both toxic chemicals and coffee brands. Suslick said the technology distinguished the vapors of 20 different toxic industrial “essentially without error” at the level that the toxins were found to be immediately dangerous to life or health.

“We just had a paper come out two weeks ago in Chemical Communications where we were able to take that sensitivity down to about five percent of the permissible exposure level,” he added. “What that means is we can monitor for 20 different analytes well below a level where you have to worry about what you are being exposed to.”

Suslick envisions the technology potentially being used as a wearable device about the size of a cell phone for the monitoring of chemicals in a work or research environment. It’s a technology that is needed since other such monitors aren’t able to distinguish one analyte from another with the degree of specificity that the opto-electronic nose can.

“People who work with radiation have a radiation badge to monitor what they are exposed to. A chemist has no equivalent,” he said. “Anybody who is working with chemicals actually has no way of routinely monitoring exposure. This kind of technology ought to be small enough to be able to do that.”

The same capability to distinguish between specific chemicals was shown with the coffee project. The idea to apply the electronic nose technology to coffee came from Suslick’s son, Benjamin, who is a senior at University High School in Urbana. Benjamin had been working in Suslick’s lab, doing mostly data analysis, for a couple of years.

“During his junior year Benjamin discovered coffee,” Suslick said with a laugh. “We could have had him work on toxic industrial chemicals but … ummm, high school student … toxic chemicals, maybe not a great idea, even if he is the boss’s son.”

So Benjamin took on the coffee project and recently a paper was published in Analytical Chemistry with Benjamin as the lead author.    

 The opto-electronic nose was able to accurately identify different coffee aromas to a high degree of specificity and accuracy, a difficult problem since roasted coffee beans contain more than 1,000 chemical compounds.

“We were not surprised that we could do that,” Suslick said. “We had already done other complex mixtures and been able to tell them apart. But I think the scientific community at large has been surprised.”

Suslick said he makes no distinction in his work between applied, translational, or basic science.

            “I find it much more important to try and distinguish between scientific research that is interesting versus boring, rather than whether it’s pure, basic or applied,” he said. “Does it change the way that I think about a problem?

“It is important to remember that science is being done by human beings and it is important for students to realize that they don’t have to separate their humanness from their science. You want the research to be fun; you want it to be exciting.”

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