Pathways to Discovery

Researcher Dahl-Young Khang prepares a sample of silicon strips in the Materials Research Laboratory at Illinois.

Whether it’s a sudden insight or careful attention to detail, the path to scientific discovery has taken many directions at the Beckman Institute.

Scientific discoveries have come from rigorous investigations of phenomena and a sudden flash of insight. They have also come from long-term studies and a fresh variation of an oft-repeated experiment. The path to scientific breakthrough can take many directions, as evidenced by a few examples of the discoveries made by researchers from the Beckman Institute.

Dahl-Young Khang wasn't trying to make scientific history. He wasn’t even trying to push the boundaries of silicon into territory scarcely imagined by researchers.

The young Rogers Research Group postdoc may have done both those things, however, by improvising a low-tech solution to a laboratory problem and by paying attention to what happened next.

Working in the Materials Research Laboratory, Khang, a postdoctoral research associate for Beckman Institute faculty member John Rogers, was repeating a process he had done many times before as part of Rogers’ wide-ranging explorations of the nexus point where electronics meet materials.

Swathed in the required cleanroom garb of thin plastic gown, cap, and boots, rubber gloves, and thick goggles, Khang gently pressed down on the little trapezoidal-shaped piece of clear, rubbery material just as he had done dozens of times before. The tiny (about an inch long) organic polymer piece of Polydimethylsiloxane (PDMS) wasn’t contacting well with the silicon substrate, however, thus preventing the experiment’s goal of transferring thin ribbons of silicon onto the piece of PDMS. So Khang decided to try using a glass vial from the lab to press down on the PDMS, much like a baker using a rolling pin.

When Khang peered at the results under a microscope the view wasn’t one of flat, straight ribbons of silicon that he was used to seeing, but a series of undulating patterns on the thin strips of silicon. Surprised and disappointed, Khang went over in his head what had happened. Two days before, he had left the silicon—etched into strips through a lab process that uses hydrofluoric acid— in his office desk for a couple of days. The exposure to room temperature left them difficult to work with—so Khang reached for that glass vial.

After seeing the results, Khang followed up on the aberration by repeating the new procedure, and by getting a better look at the wavy patterns on the silicon strips through an atomic force microscope. He then reported the news to Rogers, a member of Beckman’s 3-D Micro and Nanosystems group. Rogers said Khang was practicing good science.

“Our experience is that a lot of science is just being a careful observer of what’s happening in your experiments,” Rogers said. “This is a very good postdoc I have. Aless careful observer would have just glanced over it and said ‘oh what are these wavy things? I must not have done the printing right’ and gone back and done the printing and forgotten about it.”

Khang said his first reaction to seeing the wavy patterns was disappointment, but then his scientific curiosity took over.

“Right afterward, I thought about the possibilities,” he said. “What led to this weird shape instead of flat, beautiful images? So I started to think about what caused this kind of result.”

The finding mushroomed from experimenting with a new method for making silicon strips into testing the discovery of stretchable silicon for its electron transport properties. Research by the group showed the silicon strips could be stretched and buckled, then return to form, and still retain their electronic properties. The work eventually led to a paper published in Science in January of 2006.

The results have proven to be another breakthrough area of research for Rogers, who has been pushing the electronics envelope at every corner for the past decade or so. His work with flexible displays for electronics was what had Khang pressing down on the PDSM with a glass vial.

Now the idea for a new form of electronics— not just bendable, or flexible, but silicon-based and stretchable— has entered the realm of discovery. Gone would be the need for hard-cased electronics based on rigid silicon wafer technology. One can easily imagine, for example, an elastic wristband with the processing power of a PC, sending signals to a paper-like rollout display.

“In principal you could put any level of circuit or device into this geometry,” Rogers said. “We’ve demonstrated p-n diodes and silicon transistors, but our next step is to produce instead of strips, a 2-D plate of silicon where you have this rippled, wavy geometry in both dimensions and the plate itself supports complex integrated circuits.”

Which means stretchable silicon technology could someday become as ubiquitous as rigid silicon wafers. And it all started when some funny-looking patterns caught the eye of an observant postdoc.

Karl Hess leapt from his chair. “That’s it!”

And with that, a new technology for extending the life of microchips many times over was born.

Beckman Institute faculty member Joseph Lyding is well known for his development of the first-ever scanning tunneling microscope at the University of Illinois and for his invention of an ultrastable STM. But he is also celebrated for his many research accomplishments, one of the most famous being a collaboration with Hess that used deuterium to reduce hot electron damage in integrated circuit transistors.

Hess, an original Beckman faculty member and world expert in electron transport research, and Lyding had offices in close proximity at the Institute back in 1996 and often talked about research issues. Lyding had worked on an experiment with the STM that used deuterium instead of hydrogen on silicon and gave talks on the heat desorption effect of the method. Hess had attended one of those talks but neither he - nor any other researcher - had thought of applying it to transistor technology. Until, that is, Lyding stopped by Hess’ office one day on his way to the lab.

Hess asked Lyding about his work with silicon and hydrogen and Lyding responded: “Well, has anybody tried deuterium in transistors?” That is when the normally unassuming Hess jumped from his chair.

“It was one of those type moments,” Lyding said. “It was sort of perfectly obvious to him.”

Their collaboration resulted in a paper that received worldwide attention, and eventually the technology was patented and included in the manufacturing process by chipmakers. Lyding said the connection may have happened by chance, but never would have taken place without their shared Beckman affiliation.

“Proximity makes all the difference in the world,” Lyding said. “There’s absolutely no question about it. You can’t force interactions to occur. They have to occur naturally. There is no better way to do it. Before Beckman, Karl’s office and my office were almost a half-a-city mile apart.We saw each other more at conferences than in our offices, so the chance of that type of interaction occurring was practically nil.”

It was that interaction that led to one of those rare ‘aha’moments in science that befits a movie script.

“I guess the biggest satisfaction I get is that occasionally without knowing it, you stumble across something,” Lyding said. “And that’s exactly what we did.”

When asked to conduct a survey of research projects at the University of Illinois, Al Feng didn’t think to include his own work.After all, the survey was geared toward protecting intellectual property emanating from U of I research projects, such as the one that produced the first popular Internet browser, Netscape, a huge commercial success that didn’t benefit the university where it was born.

Feng’s work on the hearing capabilities of frogs in noisy environments was known worldwide, but it was basic science—geared toward advancing our understanding of biological systems. It wasn’t the type of work that led to commercial applications, but in 1994 Feng began to think of his research in a new way, and out of that new perspective came an advanced technology for the hearing impaired.

When Feng sat down with an outside consultant hired by the University to present the survey results, the consultant had a question: where was Feng’s work? Feng said he was working on some basic problems in neurobiology.

“I’m trying to understand how frogs extract sounds in a crowd, in a chorus specifically,” Feng told him. The consultant then mentioned a relative who was finding her new and expensive hearing aid nearly useless, especially in noisy settings.

“He became curious as to whether I would be able to contribute to solving this problem,” Feng said. “That triggered my curiosity.”

It took another push, however, before Feng became totally convinced to pursue this new research line. Feng was also working with the National Institute on Deafness and Other Communication Disorders on a long-range plan for its future goals.

“One of the problems they identified to me as one of the main problems was the performance of hearing aids in real-world environments,” Feng said. “So the two kind of reinforced the idea that this is a real problem.”

So Feng contacted fellow Beckman NeuroTech group member BruceWheeler and they took a proposal to then-Director Jiri Jonas. Funding from the Beckman Institute and two foundations got the project started, and Chen Liu was brought over from Israel to serve as a Beckman Fellow and guide the project’s early stages.

The original goal was to see if the algorithm derived from Feng’s research on how frogs separated sounds in a noisy environment could be applied to technology.

“The simple algorithm seemed to work, to do the job that we thought it might do,” Feng said. “We were frankly surprised at how effective it was.

“The rest then becomes engineering. To make it practical to use as an everyday listening device, you have to have a real-time device. So a lot of engineering effort went into that.”

The project group headed by Feng eventually grew to include a dozen researchers from speech and hearing science, electrical and computer engineering, and other disciplines.After a few years of work that included modifications on the algorithm, and some engineering innovations, the Intelligent HearingAid was developed. Hearing aid manufacturer Phonak bought the rights to the technology.

Feng is continuing his basic science research, focusing on the neural basis of sound pattern recognition in the auditory systems of frogs and bats. But translational research such as with the Hearing aid Project is now a part of his portfolio.

“I didn’t expect the meeting with the consultant to pique my interest in transferring basic science knowledge into solving engineering problems,” Feng said. “It all came together at the right time.”

This article is part of the Winter 2007 Synergy Issue, a publication of the Communications Office of the Beckman Institute.