Issue Date: August 21, 2017 | Web Date: August 8, 2017
How to create materials that mimic Mother Nature
Tucked away at the end of a labyrinthine series of corridors at Harvard University, Joanna Aizenberg’s office offers a sanctuary from the hustle and bustle of her busy laboratories. Although the space is tidy, it is not unadorned. A glass sea sponge and a brittle-star skeleton—two creatures Aizenberg has studied in her efforts to create bioinspired materials—sit behind her desk amid a sizable collection of Rubik’s cubes and other three-dimensional puzzles, objects that give a nod to her training in crystallography. All the puzzles, even the one shaped like Homer Simpson’s head, are solved, creating a color block tableau.
Aizenberg says that unraveling puzzles and solving problems has been a motivating force behind her research but that her approach has evolved over the years. “In the beginning, I’d find some interesting phenomenon and want to understand it, whether or not anything would come out of it,” she says. From there she’d figure out if what she’d discovered could be practically applied.
Take, for example, her 2004 work with the light-sensitive brittle starOphiocoma wendtii—a creature that didn’t seem to have any eyes and yet is sensitive to light. Aizenberg discovered that the brittle star is actually covered with lenses that focus light on the creature’s neural bundles. It has eyes everywhere. These structures are superior to synthetic microlenses, which are used to collect and focus light for compact imaging devices, such as photocopiers. Aizenberg applied what she’d learned about them to build better microlens arrays.
These days Aizenberg does things differently. “Rather than finding an interesting technology and having no idea how it is applicable, now we start with a problem and look for technologies to address it,” she says. This was the case with her group’s work on the omniphobic surfaces known as SLIPS, short for slippery liquid-infused porous surfaces.
Aizenberg was on the hunt for materials that could repel both oil and water to create surfaces for handling biomedical fluids, for transporting fuel, and for repelling water to prevent ice formation. She found the surfaces of Nepenthes pitcher plants were super-slippery thanks to a microtextural roughness that locks in a lubricating layer of water. When unlucky insects walk this slick surface, the water repels oil on the ends of their legs and they fall into digestive juices at the bottom of the plant’s bloom. Aizenberg’s SLIPS, which feature a porous network of Teflon nanofibers that are infused, like a sponge, with an oil- and water-repelling fluid, mimic this surface but also improve on it by repelling fluids of all types.
Aizenberg plans to discuss SLIPS and the W-Ink colorimetric sensing technology her group has developed based on the wings of Morpho butterflies during The Fred Kavli Innovations in Chemistry Lecture at the ACS national meeting in Washington, D.C., this month. Both technologies spawned start-up companies—SLIPS Technologies, which focuses on surface-enhancement products, and Validere, which does in-field crude oil testing. The two technologies are quite different, Aizenberg says, but they both share a common theme: “If you make materials that use liquid as part of their design, behavior can emerge that nobody has ever observed before.”
Just a few months ago, Aizenberg launched her third start-up, AirCrew, which is working on catalysts for air purification. “I’m very interested in basic science, probably more than technologies,” Aizenberg confesses. But when students or postdocs in her lab find a technology that they want to see commercialized, she says she’s happy to create a company around it. Besides market viability, she says the most important thing when building a new company is to have students and postdocs who can champion the technology and want to see it come to fruition.
Aizenberg spent the first nine years of her independent career as a researcher at Bell Labs (later Lucent Technologies), where her group, at its largest, consisted of two postdocs. “I was part of every experiment,” she says. “I knew every nuance of everything.” But that also meant she had to prioritize potential projects.
Ten years ago, she moved to Harvard, where she is currently the Amy Smith Berylson Professor of Materials Science at Harvard’s John A. Paulson School of Engineering & Applied Sciences, a core faculty member at the Wyss Institute for Biologically Inspired Engineering, and codirector of the Kavli Institute for Bionano Science & Technology. The switch to a university, she says, transformed how she was able to approach her research. “Suddenly there is a luxury of giving the students a long list of problems that I didn’t have the time to try,” she says, creating the opportunity to explore “a much broader range of crazy ideas.”
But the move to academia has also changed Aizenberg’s work in other ways. “My job description is actually teaching and educating students—giving them space and letting them learn from their mistakes,” she says. Ideally, she wants each of her 50-odd students and postdocs to have two projects. “One must be the craziest idea in the world: high risk, likely not to work, but if it would, it would be interesting,” she says. “But you can’t only have that, so they have another, more doable project as a backup.”
And what are those crazy ideas? The most exciting area of chemistry from Aizenberg’s perspective is in the area of materials, molecules, polymers, and hybrid systems that have the ability to adjust and self-regulate—things that can change their properties in response to their environment. These are the properties in natural systems, she says, that “we are still very far away from being able to reproduce.” But she’s working on it.
Aizenberg points out that her group is made up of scientists of many different stripes—biologists and physicists work alongside engineers and chemists. And yet, she says, “I do believe that chemistry is the central science.” Aizenberg’s training is in physical chemistry, and she now considers herself a materials chemist. So perhaps it’s not surprising that chemistry ties all her group’s projects together. “By introducing a little bit of chemistry here and there,” she says, “we improve everything.”
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