Some species of spiders, using only simple proteins as building blocks, spin a thread of silk that is stronger than a comparable strand of steel. © Markus J. Buehler/MIT
A team at MIT, researching ways to make stronger silk, makes a fascinating connection to the world of music—with implications for construction materials.
April 29, 2014—As a feat of engineering, the spider’s web is vastly underrated. Some species of spiders, using only simple proteins as building blocks, spin a thread of silk that is stronger than a comparable strand of steel. An interdisciplinary team at the Massachusetts Institute of Technology (MIT) working to understand how a spider creates this exceptional strand has made surprising connections between music and materials that hold the potential to make concrete stronger, lighter, and less expensive.
“My interest is focused on a longstanding question: how spiders and insects make this extremely strong material out of some very simple building blocks. If you take a protein and just mix it, it makes a gel, which is a very weak material,” says Markus J. Buehler, Ph.D., A.M.ASCE, a professor and the head of the Department of Civil and Environmental Engineering at MIT. “I’m trying to understand how spiders make that work. How they take protein and make steel cable from it.”
The research team includes David Kaplan, Ph.D., the chair of biomedical engineering at Tufts University, and Joyce Wong, Ph.D., a professor of biomedical engineering at Boston University. Early work centered on the proteins themselves. The research team altered DNA to create different, stronger proteins. However, this didn’t result in stronger silk. In fact, in some cases stronger proteins actually created weaker strands.
“If you take just the proteins themselves, without spinning into a fiber, it looks very strong. It’s a very good protein. But if you’re trying to spin a fiber, you cannot make a good fiber. That’s because even though the protein is very strong, it’s not able to make connections to other proteins and form a connected thread,” Buehler explains.
Looking for a way to model the interrelation of the proteins in a strand of silk, the team focused on the hierarchal structures found in many naturally occurring systems with connections on small, medium, and large scales. They found a correlation in music.
“If you describe mathematically something like silk or music, they actually have very similar structure,” Buehler says. “This is something we have recognized in a series of work for the past several years. Essentially we created this analogy model that we have put forward.”
To do this, the research group translated DNA sequences into musical notes that form, in essence, melodies. These melodies were given to composer John McDonald, the chair of the music department at Tufts, who created a longer piece of music incorporating the basic melody patterns of the DNA.
Researchers have discovered that stronger silk and softer, more
harmonious music share the same effective hierarchal
relationships on multiple scales. © Markus J. Buehler/MIT
“By doing this we can simulate, in the musical space, the spinning process,” Buehler says. “You have different proteins coming together and forming a thread. In music you have different melodies coming together and forming an impression in your brain.”
This musical model of DNA sequences led to an amazing discovery: stronger silk results in music that is more harmonious and softer while weaker silk results in hard, dissonant music. And conversely, the research team proposes that such DNA sequences can be engineered to produce stronger silk.
“It’s quite amazing to be able to hear those differences,” Buehler says. “It makes this connection between the structural properties of material [within] a space like music, which is entirely different. You wouldn’t expect that you can actually improve the structural performance by taking a musical perspective. But now you can. You can actually design new sequences of DNA based on the audio impression. The composer would be able to identify better music that creates ultimately better silk.”
Why would strong silk make better music? Buehler points to the hierarchal structure that makes both a success. “We recognized that it’s not by accident that there are correlations, because the brain is built from the same principles as silk, essentially. We can only produce what we are and what we know. Some of the things we know explicitly, but other things we know implicitly. They are innate in everything we do. We see this in the brain, we see this in music, we see this in paintings, we see this in all the living world. It’s essentially a mirror image of who we are, expressed in different ways,” Buehler says.
Buehler sees an opportunity to apply this advancement into the world of civil engineering, where projects require large amounts of materials that must last for a century. Currently he is working to apply the concepts to concrete.
“We are trying, actually, to utilize what we’ve learned from silk and building it into the concrete technology of tomorrow. If you look at concrete today, it’s essentially a random material. You get it by mixing, heating, and grinding things. It works quite well, but it’s not designed …like silk [in which] you have structures from different scales that make it so high-performing,” Buehler says.
The team will look at ways to manipulate silica and polymers to mimic the structural controls used in converting proteins into silk. This holds the potential to create a high-performing concrete that could be lighter and stronger.
“We [could then] build a structure with 20 to 30 percent less concrete,” Buehler says. “The beautiful thing about these applications is they [can involve] huge volumes. If you save only 5 percent, it’s a huge impact in dollars.”