Building Terrifically Tiny Things

By Kami Rice and Alicia P. Gregory
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In J. Todd Hastings’ world, “small” means really small, as in 100 nanometers or 1,000 times smaller than a human hair. Hastings, who is in his seventh year in UK’s Department of Electrical and Computer Engineering, works in nanotechnology and, in the simplest of terms, finds new ways to build tiny things. He’s clearly excited about his latest innovation, a nanoscale “printer,” and for good reason. It might just significantly reduce the time and expense of making nano-products.

Hastings prefaces his explanation of potentially intimidating nano-things by saying that “because nanoscale research blurs the lines between science and technology—asking scientific questions with an eye toward practical application—it crosses academic boundaries.” And Hastings feels right at home with research that crosses disciplines. With a B.S. in physics from Centre College in Danville, Kentucky, and an M.S. from Purdue and Ph.D. from MIT in electrical engineering, Hastings says he was lured back to his hometown of Lexington by the opportunity to join UK’s Center for Nanoscale Science and Engineering. The center serves as a nexus for nano-researchers from anatomy and neurobiology, chemical and materials engineering, chemistry, electrical and computer engineering, mechanical engineering, pharmacy, and physics.

Adjusting his oval, wire-rimmed glasses, Hastings smiles as he explains that the applications of nanotechnology run the gamut from traditional electronics (such as integrated circuits for computing, communications, and data storage), biochemical sensors that detect pathogenic bacteria in water or during food processing, to devices that detect cancer biomarker proteins.

He says one of the greatest challenges in nanotechnology is that there’s no standard “machine shop” for creating nanoscale devices. “Whatever your ultimate application, actually building the device is often the limiting step,” he asserts. “Prototyping—creating an original, full-scale, working model of a new device—is often the hardest part.” So Hastings asked: “Can we make it easier and faster to build new devices?”

With preliminary funding from the Kentucky Science and Engineering Foundation, and a two-year, $300,000 Young Faculty Award from the Defense Advanced Research Projects Agency (DARPA), Hastings answered that question with a resounding “Yes.” He developed and is now testing a “printer” that can rapidly try out new nanoscale designs without the lag time of a week or a month it usually takes to build a prototype.

In the hallway outside his lab, he points to a diagram of his printing process. “We have an electron beam with which we write, the way you or I would write with a pen. We have a silicon wafer—like you’d use to make a computer chip—that we write on, and,” he holds up a dime-sized stainless steel capsule, “this holds water containing dissolved gold or platinum. Our process is novel because we write underwater, and the water contains the metal inks we need to create our prototype.

 “People have used electron beams to write patterns for electronics for years, but we’re the first to do it underwater.” He says one advantage of this wet approach is purity. “In our initial experiments with platinum we observed about 90 percent purity.” He says that with older techniques, using gas instead of liquid ink, you might get 30 percent platinum and 70 percent other, undesirable materials. He adds that the purer the material on the nanoscale, the better performance you can obtain from the device. The DARPA grant is funding his efforts to determine the range of materials that can be used as ink and how to achieve the highest purity with them.

The importance of writing in these inks is that at the nanoscale the properties of these materials change. For example, Hastings explains, certain metal nanostructures strongly absorb and scatter distinct colors of light. When a pathogenic bacterium or a cancer biomarker protein binds to such a nanostructure, its color changes—giving off a vivid red or green cue that the bacterium or protein is present.

In the basement lab where the exotic-sounding electron beam “pen” resides, Hastings chuckles at the irony that the smaller the thing they are trying to make, the bigger the machine required to make it. “This is a shared piece of equipment—other scientists here use it,” Hastings says, acknowledging that a system with a million dollar price tag has to be utilized by as many scientists as possible.

This system includes a monitor, which provides an enlarged view of what the electron beam is told to “write.” A six-foot enclosed cabinet with computer components is wired to the guts of the operation—the electron beam. Located inside a chest-high, cylindrical device, the electron beam passes into a big, steel vacuum chamber. The capsule, containing water and the dissolved ink, and the silicon wafer are loaded into the vacuum chamber. “The electron beam comes into the capsule through this greenish window, through the liquid, and prints the pattern on the wafer.

“Our goal is to accelerate the pace of prototyping and decrease the expense. The equipment we use is expensive, but the materials that go into the prototype are the same things you’d use to coat a piece of jewelry with platinum or gold. It’s nothing more sophisticated than that, whereas some of the previous attempts along these lines have used really uncommon, incredibly expensive, hazardous chemicals. We’re working with much less toxic, much less expensive, readily available starting materials.”

Hastings says the DARPA-funded project is particularly exciting because “you always have more ideas than you have time and resources to try out. I hope this project will let us, and hopefully many other scientists and engineers, try out our ideas at the nanoscale and see what we can achieve with less time and effort.”

Hastings

J. Todd Hastings, electrical and computer engineering, developed and is now testing a “printer” that can rapidly try out new nanoscale designs without the lag time of a week or a month it usually takes to build a prototype.

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printer diagram

This diagram shows Hastings’ “printing” process: an electron beam passes through a membrane, into the water and dissolved gold or platinum, and “writes” the nanoscale pattern on the silicon.

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capsule

This dime-sized capsule holds water containing dissolved gold or platinum. An electron beam passes through this green window, through the liquid, and prints on the silicon wafer.

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