For a special 15th anniversary episode of its podcast series, “Stories from NNI,” the National Nanotechnology Initiative this month features an interview with physics professor Mark Tuominen, associate dean for research and innovation in the College of Natural Sciences and a fellow of the American Physical Society. In the podcast, he reflects on highlights from NNI history and some of its notable accomplishments.
Tuominen, who was instrumental in establishing the National Science Foundation’s (NSF) Center for Hierarchical Manufacturing on campus as well asthe National Nanomanufacturing Network, recalls that he has always enjoyed making things, but it wasn’t until he was a postdoctoral researcher at Harvard that he became involved in nanotechnology, then called mesoscopic physics. He made and measured hundred-nanometer-scale electron tunneling devices known as single-electron transistors which, because of their small size, could control electrons one by one, or two by two if they are superconductors. “Derivatives of these devices are now used as quantum bits or qubits in quantum computing research and development,” he notes.
Later, at UMass Amherst, he began making even smaller devices based on a phenomenon called molecular self-assembly. Soon he began a long collaboration with polymer physicist Tom Russell, an expert in manipulating the assembly of diblock copolymers, which self-assemble into periodic patterns with features at the nanoscale, Tuominen explains. He suggested that they try removing one block, leaving the other polymer in place, to create honeycomb-like structures. “I thought we could use this as a nanoscale template to fabricate arrays of nano-magnets,” he adds. “And it worked!”
That success led to work that involved combining chemical and lithographic nano-manufacturing processes, “which eventually led to our NSF Center co-led by chemical engineer Jim Watkins and myself,” he notes.
Asked to recall exciting developments in nanotechnology enabled by NNI, Tuominen says that from the early days of exploratory and fundamental science, NNI research evolved “very quickly” to realize exciting advances such as developing the ability to control electrons one at a time, for example, and to create quantum dots that control how materials interact with light.
The emphasis then shifted to how to scale such advances up from the lab bench to manufacturing scale, where great progress has been made, Tuominen says. For example, some things “unimaginable 15 years ago,” are real now, such as semi-conductor transistors for computer chips and consumer electronics now being manufactured with seven-nanometer features.
Another highlight is that “NNI changed the way people work together,” he says. “I benefitted from this synergy and the strong collaborations.” They led to interdisciplinary science that is “truly an area of convergence” leading to advances far faster than expected. The physicist reflects that he feels fortunate to be part of the growth of nanotechnology in the U.S. “with so many inspired and dedicated people.”
Finally, asked to consider what challenges may be coming where NNI plays a role, Tuominen says that there is a new emphasis in the field on advancing sustainability. “Sometimes reliable and reproducible manufacturing processes consume a lot of energy and a lot of materials. I think nanotechnology will play a role in the grand challenge of creating more sustainable processes. It has not always been a priority, though now it is a signature initiative of the NNI, and we need to work on it more.”