The future of physics will depend crucially on researchers’ ability to tackle phenomena at the mesoscale, an enigmatic realm that bridges quantum and classical physics. On that point, speakers at a special session and Town Hall meeting yesterday at the American Physical Society’s March meeting in Boston, Massachusetts, were in agreement. But what exactly is the mesoscale, and what kind of research is needed to understand it? That question brought forth multiple overlapping answers. “This is a buzz word, so you’re free to define it any way you want,” said physics Nobel Laureate Robert Laughlin of Stanford University in California, whose own answer was that the mesoscale was the scale of life, as described by emergent laws of nature that have to be discovered, rather than deduced.
‘Meso’ has been around as a catch-phrase for decades, but the term received a rush of attention at this meeting, in part because of an advisory committee charged to look into it by Bill Brinkman, the director of the Office of Science at the US Department of Energy. With a budget of nearly US$5 billion, the Office of Science is among the largest agencies supporting the physical sciences in the United States, and the largest and fastest-growing department within that office is Basic Energy Sciences, which is looking into the mesoscale as a possible area to fund.
George Crabtree, a physicist at Argonne National Laboratory in Illinois who is co-chairing the advisory committee, says that the interest arises out of a need to connect much of the nanoscale research that basic energy sciences and other agencies have supported to possible applications. “We’ve had ten years of nano but we’re not very good at relating it to the scale of human experience,” Crabtree says. Bridging the gap between basic and applied research is a focus of current Secretary of Energy Steve Chu. Although ‘meso’ is usually used to refer to distances on the scale of 10–100 nanometres, Crabtree says that it’s better thought of in relative terms, as something “in between” the nanoscale and the microscale, where the quantum meets the classical, or where systems are on the boundary between interacting and isolated systems.
With its report due in the summer, the committee has already begun to make a list of areas of study that could benefit from being considered mesoscale physics, said Crabtree’s co-chair, John Sarrao of the Los Alamos National Laboratory in New Mexico. They include the evolution of defects and accumulation of damage in materials, the behaviour of functional systems such as batteries and supercapacitors, the transport of liquids through mesoporous media such as rock — that might benefit efforts at carbon dioxide sequestration or fracking — and bioinspired assembly such as large-scale photoarrays. Commenters at the meeting suggested additional areas to look at. Physicist David Goldhaber-Gordon of Stanford University suggested studies on how densely packed charges are affected by the morphology of surfaces, and Ivan Schuller of the University of California in San Diego suggested the realm between magnetism and micromagnetics, the interactions of magnets at small length scales. Other areas of research brought to the committee’s attention include artificial leaves and self-assembly of nanoparticles. Crabtree says that mesoscale science could extend to biological research such as work on the vascular systems of plants.
Crabtree acknowledges that the advisory process is circular to some extent, with researchers providing input to the committee on their favoured research projects, which the committee then advises Basic Energy Sciences to fund. “To a large extent, that’s how the government works,” he says. But he thinks the mesoscale is a sufficiently diverse area that any programme funding it will ultimately have a broad reach, and that agencies other than Office of Science will probably start to consider research that falls under the umbrella. “If you look at what happened with nano, that’s a good model,” he says.
Image: by tonrulkens on Flickr under Creative Commons.