The Small and Large of It

The choice made by engineering faculty in the late 1980s to focus their efforts on the development of ultra-small, energy-efficient devices was, at that time, a road less traveled. Notre Dame was one of the first universities to take this step. Not only did it lead to the establishment of a center for excellence at the University (the Center for Nano Science and Technology), but faculty efforts have grown significantly over the last 20 years, as has the worldwide focus on nanotechnology.

Today, “nano” is a household word. Even elementary school children know that it means “really small.” Yet, nanotechnology remains a relatively untapped frontier with tremendous potential to impact numerous industries. Not an end to itself, this tiny enabling technology offers advancements in diagnostics, tissue engineering and drug delivery, food, textiles, and more.

To date, the most widely explored area of the application of nanotechnology is electronics. The focus has been, in large part, the transistor. It’s simple economics. The semiconductor industry, which started at nothing (the first transistor was developed in 1947, but it wasn’t until the early 1960s that integrated circuits were developed) passed the $200 billion annual revenue mark five years ago.

The downside to this incredible growth is scientifically based. For the last 40 years the electronics industry has been making semiconductor devices smaller, faster, and denser (more powerful). From cell phones and automotive GPS systems to washing machines and robotic floor sweepers, electronic devices make life more convenient. At the same time computers have become more computationally powerful, enabling more complex modeling and simulation programs for research.  

In the very near future, the electronics industry will have made the current silicon-based semiconductor as small and fast as physically possible, while still being able to operate.

Nanoelectronics offers new ways to compute, novel materials, and energy-efficient devices that can keep pace with computational needs and consumer demands. It can extend the performance of computers and communication systems. And, Notre Dame is leading some of the exciting efforts in this area. 

Engineering faculty pursuing nanoelectronics have focused their efforts on energy-efficient devices and systems with themes ranging from nanoarchitectures, modeling and measurements in nonequilibrium systems, interband tunnel transistors, and graphene transistors. In on-campus fabrication facilities, as well as through industry and government partnerships, faculty are pursuing specific projects in architectures for emerging devices, nanomagnet logic devices, lateral field-effect tunnel transistors, and extremely scaled gated tunnel transistors. They are using current frameworks and new concepts to address the challenge of the shrinking transistor.

ND faculty also are developing applications in nanobiotechology. One of the current projects features a cross-disciplinary team of 22 researchers in the colleges of engineering and science. Faculty from the fields of chemical and biomolecular engineering, computer science and engineering, electrical engineering, chemistry and biochemistry, and biological sciences are designing micro-sensing devices that will enable personalized health and environmental monitoring. The nanosensors they are creating will provide in situ monitoring for environmental and biomedical targets, as well as distributed monitoring opportunities for developing nations.

A second project explores the phenomenon known as fluorescent intermittency or “blinking.” The interdisciplinary team—composed of faculty from physics, chemistry and biochemistry, and electrical engineering, as well as researchers the Bioimaging Science and Technology Group at the California Institute of Technology’s Beckman Institute — has already discovered that the on- and off-time intervals of the blinking fluorophores follow a universal power law distribution.      

Researchers are currently performing charge fluctuation measurements on individual fluorophores to determine the cause of the blinking. If the team can find a way to control the blinking process, there is great potential for developing better and more stable multi-color imaging of diseases within individual cells. Researchers would be better able to track the development of a disease in general, and physicians could more accurately identify the location and scope of a disease in each patient.

Faculty at Notre Dame are also applying nanotechnology to address the energy challenge, specifically solar energy. Solar energy can be used for heating and to produce electricity. In the simplest of terms, a solar cell (photovoltaic device) converts sunlight into electricity. These devices are used in watches, calculators, road signs, and in remote locations not connected to an electric grid.  

Two of the main challenges in harnessing sunlight are device efficiency and cost. Photovoltaic cells are not yet commercially competitive when compared to other options. Faculty in the colleges of engineering and science and the Radiation Laboratory at Notre Dame are working to reconfigure a new generation of photovoltaic cells using nanomaterials. In particular, through the use of nanoparticles and hybrid inorganic-organic materials, they are developing nanostructure assemblies consisting of semiconductor quantum dots, metals, carbon nanotubes, and molecular clusters to better and more economically harvest light energy.

Considering these and other projects under way at the University, it is easy to be excited about the future. What is important to remember is that this is basic research. There are not annual milestones that can be guaranteed. Because of the minute scale at which work much must be conducted in laboratories, it may take years before there are viable commercial options. But there will be no solutions without this fundamental groundwork ... occurring at Notre Dame and throughout the world.

Just as with the technologies that were commercialized as a result of the space program of the 1950s and ’60s, the small steps being taken today in nanotechnology research will provide the foundation for the giant leaps yet to come as researchers continue to work on the molecular level, creating and manipulating material structures and developing new properties and devices that can be employed for the betterment of mankind.

Reprinted with permission from Notre Dame Engineer