Professor John Hart
Professor John Hart

Professor John Hart is a leading researcher in the field of carbon nanotubes, a new material that is beginning to make its way into many architectural components. An assistant professor in the University of Michigan’s Department of Mechnical Engineering in Ann Arbor, he is also the director of Mechanosynthesis Group, which focuses on synthesis, properties, and applications of nanostructures and nanomaterials. The group’s work ranges from fundamental studies of synthesis and structure, to development of novel material and device applications, to the creation of production techniques that realize these applications at commercial scales.

On October 7th, Hart will present some of the architectural applications of his work at the 2009 Innovation Conference. RECORD recently asked him to preview his talk and to provide some background on his work with carbon nanotubes (CNTs).

Innovation 2009 takes place October 7th and 8th. Click here to register.

Carbon nanotube (CNT) model
Images courtesy Mechanosynthesis Group
Carbon nanotube (CNT) model

Charles Linn: Tell use about carbon nanotubes. What are they and how are they made?

John Hart: Carbon nanotube (CNTs) are long molecules that are seamless cylinders of carbon atoms, where the carbon atoms are arranged in a hexagonal pattern (like graphite and resembling a honeycomb). Because carbon-carbon bonds are very strong, CNTs have exceptional properties—they are stronger and stiffer than steel, and only 1/4th the density of steel.

CNTs are “grown” in a high temperature furnace using small metal particles as catalyst “seeds.” CNTs are very narrow—only 1/50,000 the width of a human hair. But, if we imagine that a CNT would be a tree 1 foot in diameter, it would grow upward at over 500 miles per hour, and reach past the altitude of a typical commercial jet.

A very useful thing is that CNTs can self-organize into a “forest,” which is made of individual CNTs but can be manipulated by hand and made in a continuous process. And, the CNTs are aligned so we can take advantage of their excellent properties.

CL: You’ve been exploring the use of carbon structures for fabricating building skins. How did you get interested in architecture?

JH: Well, perhaps a long-term motivation is to “program” the properties and behavior of materials by directing their assembly at the molecular level. That’s far away though. I enjoy observing similarities between form at the nanoscale and form at the macroscale, and as a result I started thinking about the limitations of current building skins. Nanostructures including CNTs may be useful in extending both the design space and the performance space for structural materials and enabling true materials design to achieve both form and function.

CL: What can you make from carbon nanotubes that would make them unique as compared to conventional materials?

JH: Right now, we can use CNTs to enhance the properties of existing materials; for example, we can double or triple the toughness of fiber composites that are used widely in aircraft, performance vehicles, boats, and sports equipment (e.g., bicycles, tennis racquets, golf club shafts). We can also use CNTs to make transparent conductors, like those used on the touch screen of a mobile phone. We are also starting to use CNTs in batteries and solar cells, and connecting CNTs with other nanomaterials will be very exciting here.

CL: So, the range of things that you can make is quite diverse, ranging from weight-bearing structural materials to facades that can “breathe?”

JH: Well, we’re far away from making the facades that can breathe, but we’re working on a small prototype of that. Because CNTs have great properties in a number of categories, we can consider integrating energy conversion and storage (like batteries and solar panels) with load-bearing functions in a building skin. We can also use the CNTs as molecular anchors to hook them to many other materials, including biomolecules, polymers, and natural fibers. This gives us a wide design space that we may be able to work with to create some really new possibilities.