AMONG THE FIRST things you notice when you step into the corner office of Harvard University professor Joanna Aizenberg are the playthings. Behind her desk sit a sand dollar, an azure butterfly mounted in a box, a plastic stand with long fibers that erupt in color when a switch is pulled, and haphazard rows of toys. Especially numerous are the Rubik’s cubes—the classic three-by-three, of course, but also ones with four, five, six and even seven mini cubes along each edge. An eight-year-old would be in heaven.
Playing with mathematical puzzles is more or less how Aizenberg, 52, spends her days. Nobody would challenge her seriousness, though. Born in a city near Ukraine’s southwestern border, Aizenberg earned a degree in chemistry from Moscow State University and then, in 1991, fled the overt sexism and anti-Semitism of the Russian academy for a brilliant career in the West as a bioengineer, uncovering the design secrets of Mother Nature and using them in her work. She has a joint appointment at the Harvard School of Engineering and Applied Sciences, the Radcliffe Institute for Advanced Study and the Wyss Institute, a new, $125-million center at Harvard devoted to biologically inspired engineering.
Aizenberg approaches her research with a sense of play, crossing science’s traditional disciplinary boundaries with the carefree gusto of a child. She is probably best known for her collaborations with biologists, discovering remarkable engineering principles in creatures hauled out of the marine abyss. But she also works (or perhaps, plays) with chemists and architects, physicists and toy designers.
Edited excerpts follow.
SCIENTIFIC AMERICAN: Why do you look to nature for inspiration?
AIZENBERG: Every time I look at a biological system I see an amazing new example of sophisticated design. There are so many interesting strategies that nature has evolved. Nature has created all these high-quality materials and devices that scientists are simply not aware of.
For example, there is the brittle star, which is a close relative of the starfish and sea urchin. It has a hard coating, and people assumed it was blind. But we found that part of its skeleton is coated with lenses—it can see through its shell. During the day it uses a dark pigment on the lenses to limit the light, and then at night it draws the pigment back into its body. It’s like the brittle star is using sunglasses, and the lenses are better than we can make. This demonstrates an important principle: in biology, materials are often optimized for multiple functions. The shell has excellent mechanical properties because it is a skeleton, but it is also designed for optical performance. These are almost unrelated functions, from an engineering point of view, but this organism is able to combine them in a single structure.
What we do, then, is study interesting biological systems, but with the eyes of a physical scientist. This is an approach that will lead to new materials and to new devices that can change the world.
Can you tell me about your work on the deep-sea sponge?
It’s amazing all around. It lives on the ocean floor, and it grows itself a skeleton made of glass. When people make glass, they do it at 2,000 degrees Celsius, but somehow these organisms synthesize glass fibers at ambient temperatures.
Then, at the sponge’s base, where it is attached to the ocean floor, it has a crown of thin strands that behave like nearly perfect optical fibers, which guide light from one end to the other. We think that we invented optical fibers 60 years ago; nature created optical fibers—from the same material we use—half a billion years earlier.
But the sponge lives in darkness. Why would it create such a sophisticated fiber-optical system? It turns out that it lives symbiotically. Bioluminescent bacteria live on the sponge, and their light shines through the fibers. The crown of illuminated fibers acts like a beacon, attracting other life in the darkness. Then a pair of shrimp live inside the sponge—protected by this illuminated glass house, feeding on all the things that are attracted to the light. The waste from the shrimp then helps to feed the sponge. It’s a complete system.
How did you find the sponge?
I was at a scientific conference in San Francisco, and I went to a gem shop. I am totally addicted to those stores. They had the sponge, lying in a very dark corner, with its crown of fibers all lit up. The entire thing was so beautiful. I picked it up, then did what I really love, which is to collaborate with marine biologists.
What do you think we can learn from this organism?
The deep-sea sponge offers us a lesson in improving the strength of inherently poor and fragile materials. Glass is fragile, but this sponge is not fragile at all; you can step on it, and nothing would happen.
The way nature achieves this is by combining different structural strategies, one on top of the other. It combines fibers to make a laminated material. These are built into struts, which are combined to form squares, and these squares are then surrounded by a glass-fiber cement. It’s glass inside of glass inside of glass, but the sponge combines them to create a very strong material that overcomes glass’s natural brittleness.
You can also look at the sponge as a green building, with a pattern of open windows on its surface. It makes me wonder, for example, whether you could make a skyscraper where every 10th floor was open so that energy could be harvested from the wind.
For engineers, what are the advantages of looking to nature, and what are the potential pitfalls?
Nature can show engineers the vast diversity of solutions for complex technological problems. Not all of them will be practical. One strategy inspired by nature might turn out to be so costly in terms of the materials or the energy needed that we can’t use it. On the other hand, some natural solutions might be as good as what engineers do now, or a little bit worse, but much cheaper. So nature provides a whole range of interesting solutions to explore.
But we have to be careful. Nature has a very limited selection of materials. Biology doesn’t have steel. We do. So I don’t like to call my field “biomimetics,” because I don’t want to mimic biological structures. I would rather call it “bioinspired engineering” because what I’m doing is taking a concept from biological design, not the specific solution. I would not want to actually create a brittle star; I want to create a roof element that has lenses that collect light and that is mechanically stable. I’m not using the same materials as a brittle star, but I’ve stolen its strategy.
Why is nature so accomplished as an engineer?
Life is about function: it has to create robust solutions to the challenges it faces, whether it’s how to divide, how to self-heal or how to produce things that will last. Nature also has a big advantage: millions and millions of years of evolution. We haven’t had that time. The other thing is that in nature, there is no other option. It is survival of the fittest. If you are a bad engineer, you will be removed from the world. If you make a mistake, you die.
Did your parents influence your decision to become a scientist?
My father was a construction engineer who designed and built bridges and roads. My mother was a doctor who focused on infectious disease. They both inspired me, in many ways. My mother was in medical school in the 1950s [in the Soviet Union], when Stalin forbade any work on genetics, and she led a group of students that would meet in secret to study DNA. She was fearless, the most strong-willed person I have ever known.
When I was a child, I had polio, and my legs were paralyzed for a long time. My mother spent so much time talking to me, showing me the world I could see out of my window. “Look at how the trees grow, the shapes they make,” she would say. “Look at the patterns the water makes as it rushes by.” It was really wonderful.
How did you become interested in chemistry?
I know it sounds funny, but one of my favorite things to do as a child was solving mathematical problems. When I was in middle school, I earned a little money from a journal devising math problems for other students. When I arrived at Moscow State University, I met with people from the departments of mathematics, physics and chemistry. From these discussions I concluded that math is just math. Physics is just math plus physics. But the field of chemistry provides such breadth. And the more I have studied chemistry, the more I have come to feel that chemistry is the key science. It has branches going everywhere. It’s an amazing place to be.
Does your work always start with some plant or animal that interests you, or do you ever set out with particular applications in mind?
My group has become interested in “wettability,” which refers to how much a material attracts or repels liquids. What we’d like to do is to design surfaces with controlled wettability. For 15 years everybody has been looking to the lotus leaf for inspiration because water naturally flows right off it. But the community has realized that it’s going to be extremely challenging to use the secrets of the lotus leaf in a practical material. The materials turn out to be too expensive and too sensitive to damage.
So we have turned to another natural model: the pitcher plant. The pitcher plant is carnivorous. It has an incredibly slippery surface. If an ant climbs on, it will just slide into the flower, where it is trapped and digested. Using this as inspiration, we have built a similarly slick surface. It could be used to coat the inside of oil pipelines, making the oil much easier to pump. For biomedical applications it would mean that blood would flow well, and no bacteria could build up anywhere. Another potential use is as a treatment for walls to resist graffiti. The paint would just slide right off. It would seriously irritate those artists.
What do you think we will see from materials science in the coming decades?
We know how to make strong materials. We know how to make optical materials. What we do not know how to do well is to manufacture materials that respond to the environment, that can automatically change their properties, that can self-heal, that can change appearance when necessary. We need materials that have reversible adaptive behavior.
For example, we have a material that could potentially be used for “smart” clothes. It naturally changes with the humidity, attracting moisture when it’s extremely dry outside but repelling water when it’s raining. You can imagine many applications for adaptive materials. If the weather were cold, then you’d want the windows to direct any available heat into the room. But on a hot summer day you’d want the same material to become reflective, keeping the room comfortable.
Creating these kinds of materials is the big challenge for the 21st century.
Having studied nature so much, do you look at it differently?
I would say so. I am really interested in how patterns are formed. So if I am walking on the beach, I keep looking at how the waves come in. Or I can spend all my time looking at the lines the receding waves leave behind. They make beautiful shapes. I might think about how the shapes are related to other beaches or to the size of the sand grains.
I truly love the ocean. The life there is so diverse and mind-blowing. And I’m convinced that every organism has something to teach us.