By Daniel Dunaief
Throw a batch of LEGOs in a closed container and shake it up. When the lid is opened, the LEGOs will likely be spread out randomly across the container, with pieces facing different directions. Chances are few, if any, of the pieces will stick together. Attaching strong magnets to those pieces could change the result, with some of the LEGOs binding together. On a much smaller scale and with pieces made from other parts, this is what researchers who study the world of self-assembled materials do.
Scientists at the Center for Functional Nanomaterials and at the National Synchrotron Light Source II at Brookhaven National Laboratory experiment with small parts that will come together in particular ways based on their energy landscapes through a process called self-assembly.
Every so often, however, a combination of steps will alter the pathway through the energy landscape, causing molecules to end up in a different final configuration. For many scientists, these so-called nonequilibrium states are a nuisance.
For Kevin Yager, they are an opportunity. A group leader at the CFN who works closely with the NSLS-II, the McGill University-educated Yager wants to understand how the order of these steps can change the final self-assembled product. “In the energy landscape, you have these peaks and valleys and you can take advantage of that to move into a particular state you want,” Yager said. “The high level goal is that, if we understand the fundamentals well enough, we can have a set of design rules for any structure we can dream up.”
At the CFN, Yager manages a nanofabrication facility that uses electron-beam lithography and other techniques to make nanostructures. He would like to fabricate model batteries to show the power of nanomaterials. He is also determined to understand the rules of the road in the self-assembly process, creating the equivalent of an instruction manual for miniature parts.
In future years, this awareness of nonequilibrium self-assembly may lead to revolutionary innovations, enabling the manufacture of parts for electronics, drugs to treat disease and deliver medicine to specific locations in a cell and monitors for the detection of traces of radioactivity or toxins in the environment, among many other possibilities.
Yager’s colleagues saw considerable opportunities for advancement from his work. Nonequilibrium self-assembly has “significant potential for a broad range of nanodevices and materials due to its ability to create complex structures with ease,” Oleg Gang, a group leader in Soft and Bio Nanomaterials at the CFN, explained in an email. Yager is an “excellent scientist” who produces “outstanding results.”
One of the things Yager hopes his research can develop is a way to “trick self-assembly into making structures they don’t natively want to make” by using the order of steps to control the final result.
As an example, Yager said he developed a sequence of steps in which nanoscale cylinders pack hexagonal lattices into a plane. These lattices tend to point in random directions as the cylinders form. By following several steps, including sheer aligning a plane and then thermal processing, the cylinders flip from horizontal to vertical as they inherit the alignment of the sheered surface. Flipping these cylinders, in turn, causes the hexagons all to point in the same direction. When Yager conducted these steps in a different order, he produced a different structure.
Broadly speaking, Yager is working on stacking self-assembling layers. In his case, however, the layers aren’t like turkey and swiss cheese on a sandwich, in which the order is irrelevant to the desired final product. Each layer has a hand in directing the way the subsequent layers stack themselves. Choosing the sequence in which he stacks the materials controls their structure.
Yager is working with Esther Takeuchi and Amy Marschilok at Stony Brook University to develop an understanding of the nanostructure of batteries. Gang suggested that Yager’s expertise is “invaluable for many scientists who are coming to the CFN to characterize nanomaterials using synchtrotron methods. In many cases, it would probably be impossible to achieve such quantitative understanding without [Yager’s] input.”
Yager and his wife Margaret Schedel, an associate professor in the Department of Music at Stony Brook University who is a cellist and a composer, live in East Setauket. The couple combined their talents when they sought ways to turn the data produced by the CFN, the NSLS and the NSLS-II into sound.
Scientists typically convert their information into visual images, but there’s “no reason we can’t do that with sound,” Yager said. “When you listen to data, you sometimes pick up features you wouldn’t have seen.”
One of the benefits of turning the data into sound is that researchers can work on something else and listen to the collection of data in the background, he said. If anything unexpected happens, or there is a problem with a sample or piece of equipment, they might hear it and take measures more rapidly to correct the process. “This started as a fun collaboration,” Yager said, “but it is useful.”
Schedel is working on sonifying penguin data as well. She also sonified wave data on Long Island. “By listening to the tides quickly, larger patterns emerge,” she said, adding that Yager thought the idea was theoretically interesting until he listened to misaligned data and then he recognized its benefit.
Schedel’s goal is to see this sonification effort spread from one beamline to all of them and then to the Fermilab near Chicago and elsewhere. She wants sonification to become “an ear worm in the science community.”
While Schedel introduced Yager to the world of sound in his research, he introduced her to sailing, an activity he enjoyed while growing up in the suburbs of Montreal. When she sails with him, they are “half in and half out of the boat,” Schedel said. It’s like two people “flying a kite, but you are the kite. You have to learn how to counterbalance” the boat. They hike out so they can take turns faster without tipping over, she said.