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A New Field of Materials Design is Born

February 7, 2013

CEE Assistant Professor Steven Cranford recently received a Haythornthwaite Research Initiation Grant for his project titled “Multi-phase Topologically Controlled Structural Fuses Inspired by Nature.” This grant program awards university faculty engaged in research in theoretical and applied mechanics who are at the beginning of their academic careers. The proposed work is the initial study of a long-term initiative by Prof. Cranford to exploit the functionality of biomechanical systems within macroscale structural engineering, such as seismic resistant systems, through an integrated approach of computational modeling, theoretical formulation, and experimental validation. Congratulations to Prof. Cranford!


Source: News @ Northeastern

Each time a spider draws silk from its spin­neret to create a new web, it also draws on more than 400 mil­lion years of evo­lu­tion. Spi­ders have evolved to pro­duce a library of silks, each using a dif­ferent com­bi­na­tion of amino acids to address a par­tic­ular func­tional need. Some silks are sticky, making them per­fect for catching prey. Others are soft and duc­tile, good for mothers to use in cre­ating nests for their off­spring. Most are pro­por­tion­ally stronger than steel and even tougher than Kevlar.

There has to be some­thing about the mate­rial com­po­si­tion of silk that ide­ally suits it to make web-​​like struc­tures,” said Steve Cran­ford, a newly appointed assis­tant pro­fessor of civil and envi­ron­mental engi­neering.

As a grad­uate stu­dent at MIT, Cran­ford studied spider silks and other bio­ma­te­rials under the tute­lage of Markus Buehler. “We didn’t want to just figure out how spider silk works, what we wanted to do was learn from spider silk and apply it else­where,” said Cranford.

By better under­standing the way nature uses mate­rials to build robust struc­tures, Cran­ford and his col­leagues hope to create their own stronger syn­thetic mate­rials and struc­tures. Cran­ford, who has a back­ground in struc­tural engi­neering, noted that this is a com­pletely dif­ferent approach from tra­di­tional struc­tural engi­neering, in which mate­rials such as con­crete and steel are chosen based on our expe­ri­ence with them, not their suit­ability for the system.

The fruits of their labor have cul­mi­nated in the estab­lish­ment of an entirely new field of research, which Cran­ford, Buehler, and col­leagues from the Uni­ver­sity of Twente in the Nether­lands have dubbed “mate­ri­omics.” Just as genomics refers to the entire genome as a col­lec­tive whole greater than the sum of its parts, mate­ri­omics con­siders all the parts in a struc­ture as a single entity with emer­gent properties.

For instance, bone is typ­i­cally con­sid­ered a com­posite mate­rial, a com­bi­na­tion of both min­eral and pro­tein, but if you sep­a­rate the two, it’s no longer bone, Cran­ford explained. Steel, con­crete, and a rein­forced beam are all exam­ples of other com­posite mate­rials, each con­tributing to a greater struc­tural whole. “So couldn’t you just con­sider an entire building as a mate­rial?” Cran­ford asked. “What do you con­sider the mate­rial and what do you con­sider the struc­ture? You can’t sep­a­rate the two.”

Ear­lier in his career Cran­ford studied seismic design and building failure. But seeking to make an impact in the bio­log­ical sci­ences, he ulti­mately came to view mol­e­cules as tiny struc­tures, sus­cep­tible to the same forces that impact build­ings and bridges. “At a small enough scale, atoms and bonds are just little struc­tures,” he said, “From the right per­spec­tive, every­thing starts to look like a beam.”

Pro­teins like spider silk have inspired bio­mimetic research pro­grams seeking to develop every­thing from a better heart stent to a lighter bul­let­proof vest. But the dif­fer­ence between nat­ural mol­e­cules and syn­thetic struc­tures is that the former are the result of eons of evo­lu­tionary fine-​​tuning. Bil­lions of trial and error exper­i­ments ensure that the spe­cific sequence of amino acids in struc­tural web silk is ide­ally suited for its pur­pose. The key for engi­neers lies in under­standing how the mate­rial can con­tribute and enhance per­for­mance, rather than in choosing mate­rials that meet arbi­trary struc­tural requirements.

When designing syn­thetic mate­rials for use in bio­log­ical set­tings, say Cran­ford and his col­leagues, researchers should con­sider struc­ture and func­tion as two sides of the same coin. Steve Cran­ford, an assis­tant pro­fessor of civil and envi­ron­mental engi­neering, studies spider silk and other nat­ural mate­rials for insight into designing more robust syn­thetic structures.