Inspired by Viruses and Butterfly Wings, UMass Amherst Researchers Make Leap Forward in Mimicking Nature’s Incredible Engineering Skill for New Class of Materials

A team of researchers led by the University of Massachusetts Amherst has drawn inspiration from a wide variety of natural geometric motifs-including those of 12-sided dice and potato chips-in order to extend a set of well-known design principles to an entirely new class of spongy materials that can self-assemble into precisely controllable structures. Their theory and computational model, published in the Proceedings of the National Academy of Sciences, allows for maximum design economy, or the largest possible structure using the fewest number of programmable, self-assembling pieces.

One of the holy grails of materials science is to emulate nature's ability to form robust, complex self-assembling materials that can then create structures capable of a wide range of functions. Think of the crystalline nanostructures that form on a butterfly's wings and whose precise form and size determine exactly which wavelengths of light to reflect, giving different species their distinctive markings.

"We were inspired by virus self-assembly," says Greg Grason, professor of polymer science at UMass Amherst and the paper's senior author. "Though some viruses can pose risks from a health perspective, they have an incredible 'self-closing' design. Many have a rigid, highly symmetric spherical shell, and this shell is built of the fewest number of protein arrangements possible. The shell is also just the right size-any bigger, and it wouldn't be able to infect its host; any smaller, and the virus wouldn't be powerful enough. We want to be able to create materials that can economically self-assemble into the perfect shape, just like viruses-except we want to engineer entirely different types of geometries."

Grason and his team, including colleagues at Brandeis and Syracuse universities, as well as co-lead authors Carlos M. Duque and Douglas M. Hall, both of whom completed this research as part of their graduate studies at UMass Amherst, are hardly the first to be inspired by viruses. Back in the 1960s, a pair of structural biologists named Donald Caspar and Nobel Prize winner Aaron Klug, inspired by Buckminster Fuller's famous geodesic domes, realized that the structure of his domes also described virus shells. They went on to derive a set of design principles, called the Caspar-Klug symmetry principles, that describe how to build a structure enclosing the largest possible volume with the fewest number of building blocks.

"Inspired by the beauty and elegance of the Caspar-Klug construction for icosahedral viral shells, we developed a roadmap to find economical design rules that can help us engineer a wide range of very useful nanostructures," says Duque.