Dr. Joanna Aizenberg leads the adaptive material technologies team at Harvard University’s Wyss Institute for Biologically Inspired Engineering. Translation: She and a group of colleagues adapt nature’s best ideas to solve current human engineering challenges. Her work focuses on organisms’ abilities to construct useful things out of inorganic materials to help them survive in an ever-changing environment. Txchnologist reached her via email.
What are some examples of biologically inspired engineering and design that already exist and are part of people’s lives?
Although they probably didn’t realize it, civilizations have been building brick walls for thousands of years using the same concepts mollusks use to construct their shells. More recently, as work by many groups has provided detailed insight into how these shells’ chemical construction—alternating layers of hard mineral and elastic organic interlayers—makes them tougher than anything built by humans, we’ve taken the mollusks’ ideas and used them to revolutionize how we design our own buildings to make them both sturdier and lighter.
The optical fibers used in telecommunications systems are a similar story, and this is an example that is closer to my heart. Engineers invented fiber optics several decades ago, but then we discovered glass sponges living at the bottom of the ocean have been doing the same thing for millions of years—and using them to build illuminated glass houses of the deep. Now that we’ve made the connection, we’ve been able to learn from the “natural” experts how to construct nearly perfect light guides that use less energy and optimize them for mechanical robustness at the same time.
In many other cases, though, the idea started with something we noticed in nature and went from there. The study of how termite mounds are constructed directly inspired architects to design buildings that maintain comfortable living temperatures with little or no reliance on conventional heating and cooling, such as the Eastgate Building in Zimbabwe. And the color of butterfly wings has inspired computer color displays that are powered by ambient light.
What are the types of materials currently being researched that hold the most promise for near-term deployment in city buildings or infrastructure?
We have materials that prevent ice from forming by mimicking the surfaces of water-repellent lotus leaves. These are being developed for use in ice-free power lines, windshields, rooftops, pipes, planes and more. We also have a self-healing, ultra-slippery material inspired by the carnivorous pitcher plant, which repels everything from ice to bacteria, oil, blood, insects and dust. We can expect it to appear as self-cleaning windows and anti-graffiti surfaces, on solar cells or road signs, inside transport pipes for fuel and water, in district heating and hospitals as self-sterilizing medical equipment, and inside ketchup and shampoo bottles, to name just a few examples.
We’re also creating a whole range of adaptive materials that respond to their environment—smart windows that let light in when it’s cold and keep it out when it’s hot, stress-responsive coatings for buildings and bridges that change color to reveal tiny cracks and clothes that absorb moisture in dry weather and repel water in the rain.
How will these materials alter the landscape or the ways people interact with the city?
The common feature of these materials is that they require no external energy. Instead of heating a window to de-ice it, the surface will remain ice-free by itself. Instead of complicated electrical systems to regulate the heat, windows and walls will be built from materials that self-adapt their reflective and thermal properties to maintain a constant temperature.
Based on your knowledge of the current state of biologically inspired engineering, what could the urban world look like in 50-100 years if you were designing it?
We are dreamers and believers. Our vision is building as organism: Using principles of self-assembly and self-organization applied to the urban world; recognizing that materials performance should be adaptive, responsive and self-optimizing; and understanding that performance emerges from the dynamic interaction between different building systems, the environment and occupants.
Imagine buildings and the entire urban world that adapt to their environment, harvest energy, collect and deliver water, self-heal, collect and regulate light, repel ice and moisture, self-clean and resist biofouling by mold or infestation, change color and self-optimize/reconfigure their spaces. Nature can do it and we can do it, too. All these technologies take us a long way toward the goal of the sustainable city.
UPDATE: This article was altered on June 6, 2012, to include a discussion of early biological inspiration in engineering.
Top Image: Courtesy Flickr user inoc