Say No to Cracks

“Not everything innovative has to be complicated!” says Rose-Hulman’s Interim Chemical Engineering department chair Dr. Adam Nolte. His recent discovery, along with Dr. Daeyeon Lee, Assistant Professor of Chemical and Biomolecular Engineering at the University of Pennsylvania, may impact the future of battery technology and the broader area of energy conversion and storage, as well as lower costs in technologies that involve the structural manipulation of light, such as anti-reflection coatings for eyewear.  Their work was published this month in the journal Nano Letters.

A new method utilizing subsequent depositions of thin crack-free nanoparticle layers is demonstrated to avoid the formation of cracks within silica nanoparticle films. Using this method, films can be assembled with thicknesses exceeding the critical cracking values. Reprinted with permission from Avoiding Cracks in Nanoparticle Films. Copyright Sept. 1, 2012 American Chemical Society.

Read a more in-depth summary of the Lee/Nolte research in the article “Just Say No to Cracks.”

“This work was inspired in part by idea exchange between Prof. Lee and myself,” Nolte explains. “I was working with Chemical Engineering students to design anti-reflection coatings from particles, and Prof. Lee is interested generally in the concept of nanoparticle films.  We began trading ideas about how particle films could be incrementally constructed by spin-coating deposition since a thin layer of particles would not redissolve when new layers were put on top of it (which is a problem with polymer films, which Prof. Lee and I also both work with).”

The typical method for creating crack-free particle coatings is to deposit a single thick layer with added binders or to use complicated drying techniques; however, these methods can change the chemistry of the coating and add cost and production complexity. The innovation in the Lee/Nolte research — creating a thicker layer by adding many thin layers one on top of another — was not only a simple shift, but it led to new discoveries about the properties of these films, which may have additional,  far-reaching consequences. The team discovered, in addition to the fact that the layer would not re-dissolve when other layers were added, that a layered film is more resistant to cracking at thicknesses where conventional particle films will crack apart like a desert wadi.

“This is an example of trying something really simple and having it work,” Nolte says. “We essentially found that building a nanoparticle film in ‘baby steps’ instead of depositing the whole thing at once can delay the onset of cracking, and potentially provide a more useful product.  I think it is a good example that innovative thinking can happen by approaching a problem from simple but clever angles.”

Nolte’s story is also an example of how engineering faculty, with a key imperative to provide undergraduate research opportunities, find a nice balance between teaching and  being on the leading edge of discovery. Nolte gained ideas while working with students, and students gain a front row seat on the marathon of steps leading from idea to the development of new technologies.

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