From the Redwood Forest, to the gulf stream waters – Biologically Inspired Engineering at the Wyss Institute is creating a more sustainable future
By Lindsay Brownell
For the 55% of humans who now live in cities surrounded by concrete, asphalt, glass, and steel, it can be easy to forget the diversity of other types of environments on Earth. Windswept glaciers, vast canyons, gnarled forests, steaming jungles, underground caves, sunbaked deserts, and the vast oceans all support their own unique ecosystems. What they have in common, however, is significant damage due to human activity: pieces of plastic permeate the ocean and clog the guts of seabirds, whales, and fish; smog produces acid rain that can harm plants and animals; clear-cutting forests increases erosion and causes nutrient-rich soil to be washed away; and toxic chemicals produced by a wide variety of industries find their way into waterways, into animals, and into us.
While policies and regulations over the last half-century like the founding of the United States Environmental Protection Agency in 1970 and the Clean Water Act of 1972 have helped preserve and rehabilitate our natural environment, they are not enough. With the world’s population expected to hit 10 billion by 2050, human consumption of natural resources is predicted to double as the middle and upper classes grow and demand a more industrialized lifestyle.
“Humans have evolved to exist within a very narrow range of environmental conditions and, so far, Earth is the only planet that we’re sure we can survive on. The climate is changing and we are consuming natural resources at an alarming rate, so it is more urgent than ever that we find ways to reduce our environmental impact so that our species can continue to live on Earth for millennia to come,” said Donald Ingber, M.D., Ph.D., the Founding Director of the Wyss Institute for Biologically Inspired Engineering at Harvard University. Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School (HMS) and the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS).
Scientists working in and across several of the Wyss Institute’s interdisciplinary platforms are developing new technologies that can be deployed alongside conservation efforts to preserve and restore the environment, taking inspiration from Nature itself to create sustainable solutions to human-created problems that threaten our land, sea, air, and human-created “built environment.”
Dry land covers only one-third of the surface of our planet, but it’s home to over 7 billion humans, the vast majority of the food we harvest, and an untold number of species of plants, animals, fungi, and bacteria. The amount of land available for all those organisms to share is getting smaller, however, due to factors such as increased soil erosion caused by intensifying storms and the agriculture, mining, and construction industries, and rising global sea levels that threaten to swallow beaches, estuaries, and coastal cities. Mitigating these large-scale environmental threats currently requires the time- and cost-intensive use of heavy machinery to build massive structures like dams and retaining walls, and is limited to areas that those machines can access.
Senior Research Scientist Justin Werfel, Ph.D. and Computer Science Fellow Nathan Melenbrink working within the Wyss Institute’s Bioinspired Robotics Platform were experimenting with using a “swarm” of robots to install foundations for bridges and other large structures when they realized that their system – based on driving “sheet piles” (flat, thin, interlocking sheets of metal) into the ground – could also be applied to environmental restoration. Sheet piles can be used to form check dams, which are commonly used along shorefronts, riverbeds, and other vulnerable ecosystems to prevent erosion, reduce flash flooding, and promote groundwater recharge.
Inspired by insects like termites and ants that collectively build structures many times larger than themselves, the researchers created a sheet-pile-driving robot dubbed Romu. Romu drives sheet piles into the ground by leveraging its own weight and a vibrating hammer. By forcing each sheet pile into the ground in a multi-step process, adjusting its grip to a higher position on the pile each time, the robot can potentially install a pile taller than its own height.
“Many sensitive environments would be vulnerable to damage by the massive machines currently used to drive industrial piles,” said Werfel. “Dividing the task among several smaller, more efficient robots that can work in parallel would allow us to more quickly and sustainably secure vulnerable habitats without the need for extensive supporting infrastructure.”
The researchers have tested Romu both in a sandbox in the lab and on a nearby beach, and computer simulations have shown that a swarm of Romus could help retain soil to reduce erosion and aid in land management. “We’re hopeful that Romu can encourage a lot of industries that traditionally manage ecosystems with heavy machinery to consider the benefits that these kinds of distributed, automated interventions could bring,” said Melenbrink.
It is commonly said that we know less about the bottom of the ocean than we do about the surface of the Moon, though it covers two-thirds of our planet. Robert Wood, Ph.D., a Wyss Core Faculty member and Co-Leader of the Bioinspired Robotics Platform whose lab builds soft robots including artificial muscles, soft sensing skins, and wearable robots, didn’t think much about the ocean in his daily life until he met marine biologist David Gruber, Ph.D. at an event celebrating their nominations as National Geographic Emerging Explorers in 2014. Gruber, a professor at Baruch College CUNY, presented a video of his team attempting to use a heavy, clunky research submarine claw to pick up a delicate bottom-dwelling sea creature. “Rob came up to me afterwards and was completely unimpressed that this was the state-of-the-art for marine biologists…and started peppering me with engineering questions about the gripper. The conversation ended with him asking me, ‘Have you ever heard of soft robotics?’ And the answer was ‘no.’”
“The motivation to build robots that are soft and pliable grew out of the recognition that hard-bodied robots and other machinery are limited in their mobility and dexterity, which will only become a greater stumbling block as humans interact more and more closely with robots in everyday life and demand even greater precision from them,” said Wood, who is also the Charles River Professor of Engineering and Applied Sciences at SEAS. “It just so happens that such abilities are also a perfect fit for interacting with soft-bodied animals underwater.”
The two researchers applied for an Innovation Challenge Grant through National Geographic a few months later, kicking off a years-long collaboration that has produced soft robotic grippers capable of capturing a range of delicate creatures – from jellyfish to sponges to corals – and letting them go without harm. One design has finger-shaped actuators with channels that can be filled with seawater to make them bend and gently enclose a sample, while another twists into a spiral shape to grip slender targets like sea whips. Gruber and Wood hope to expand their work to create full “underwater labs” where sea creatures can be studied in their natural habitat.
“The vision that Rob and I have is that one day we could enclose an animal underwater, collect a few of its cells so we can sequence its genome, scan the animal and 3D-print a model of it back at the surface, then let the animal go. We would get more information in that really delicate manner than we would if we collected and killed that animal,” said Gruber.
“If you really want to study an animal, you need to do that when it’s in its natural state, and if you start poking and slicing it, you’re not going to get a complete picture of what’s really going on with it. We hope this work can serve as an example of how we can delicately, gently, and respectfully interact with creatures that are sometimes so old and so rare that our current methods of studying them actually endanger them,” added Wood.
While the organisms Wood and Gruber are studying are rarely seen by humans, several aquatic creatures are common annoyances in coastal areas and ocean-based industries, including barnacles, mussels, algae, and sponges, all of which are considered “biofouling” species. These clingers-on can destroy manmade structures and cause increased drag on boats as they move through the water, increasing the fuel needed to ship cargo long distances. This seemingly superficial problem actually has a large impact: the US Navy alone spends ~$1 billion per year on antifouling efforts. Existing products to combat biofouling are only marginally effective at preventing organisms from attaching and are frequently toxic to marine life, both their target species and those that simply swim too close.
Across the street from Wood’s lab in Cambridge, MA, the leader of the Institute’s Adaptive Material Technologies Platform has developed a non-toxic alternative that biofouling species simply can’t grip, inspired by the slippery lip of the pitcher plant. Core Faculty member Joanna Aizenberg, Ph.D. has long been fascinated by what properties make a material behave the way it does, and how to tweak those properties to make them adaptive to different conditions. Carnivorous pitcher plants send their prey sliding to their doom inside the plants’ “stomach” thanks to a unique leaf structure that repels nearly any substance, including insects’ feet. Looking more closely at this phenomenon, Aizenberg and her lab discovered that the plants’ secret is a hard, porous base surface infused with a liquid. The attraction between the materials keeps the liquid in place on top of the porous layer, effectively making attaching something to the surface as difficult as trying to stick a piece of tape to water.
“Once you start looking at natural systems carefully, you realize that a lot of them have found really elegant solutions to problems that are also present in various human-driven activities,” said Aizenberg, who is also the Amy Smith Berylson Professor of Material Sciences at SEAS. “Mimicking these systems, rather than trying to develop entirely new approaches from scratch, takes advantage of millions of years of Nature’s R&D efforts.”
Aizenberg and her lab engineered their own material inspired by the pitcher plant, called Slippery Liquid-Infused Porous Surfaces (SLIPS), that incorporates a lubricating liquid into a solid base and is exceptionally repellent, robust, and self-cleaning. It has been licensed to Adaptive Surface Technologies, Inc., which has commercialized its first product as a non-toxic anti-fouling coating for ships that consistently prevents biofouling for more than two years.
“SLIPS-based antifouling coatings are many times more effective at preventing marine life from attaching to underwater structures, which helps to protect ocean species and also reduces the fuel used by ships, because they become more hydrodynamic,” said Aizenberg. In addition to its underwater use, SLIPS can also be applied to metals, plastics, optics, textiles and ceramics, and could be used to reduce buildup within pipes, stains on clothing, and the transmission of diseases via medical equipment.
Humans might not spend much of our time underwater, but we are constantly surrounded by and breathing the ocean of air that is our planet’s atmosphere. Just as news of the Great Pacific Garbage Patch has spurred awareness of the toll of human impact on marine ecosystems, recent studies about the impact of air pollution are driving interest in reducing it. The World Health Organization estimates that seven million people are killed every year due to air pollution, and Greenpeace Southeast Asia has reported that the global medical cost of polluted air exposure is in the trillions of dollars annually.
Most of the pollution released into the air comes from the burning of fossil fuels like coal, oil, and gasoline. These fuels can contain up to 150 different chemicals, and the byproducts of burning them include poisonous carbon monoxide gas, VOCs (volatile organic compounds), and nitrogen oxides that create smog. The most popular method for reducing these byproducts is installing devices called catalytic converters in smokestacks, exhaust pipes, and automobiles to transform those harmful compounds into more benign gases before they are released into the environment.
However, catalytic converters are expensive because they use precious metals like platinum as catalysts, restricting their use to high-value industries. There have even been reports of catalytic converters being removed from cars so the platinum inside them can be sold, resulting in much more highly polluting automobiles. In addition, conventional catalytic converters are not as efficient as they could be, because the catalyst particles are embedded in the converter randomly, meaning some of them never come into contact with the air they are supposed to clean.
A solution to this problem has also been found in the Wyss’ Adaptive Material Technologies Platform, once again inspired by a structure found in nature: butterfly wings. Zoom in closely enough on a butterfly, and the surface of its wings is revealed to be a porous architecture that makes them aerodynamic, hydrophobic, and creates their colors by scattering light. Tanya Shirman, Ph.D., and Elijah Shirman, Ph.D. realized that by mimicking this structure, they could create a scaffold into which catalyst particles could be precisely placed to maximize their contact with dirty air, thus requiring less precious metal and improving catalytic converters’ ability to remove pollution.
“Manufacturers of catalytic converters spend 70-90% of their total costs on precious metals, so if we can bring that cost down, clean air will become more accessible to everyone,” said Tanya Shirman, who is a Research Associate at the Wyss Institute. “One of the best things about our technology is that it’s essentially plug-and-play: it can integrate seamlessly into existing manufacturing processes, and instantly provides an improvement for both the manufacturer and the environment,” added Elijah Shirman, a Visiting Scholar in the Aizenberg lab at SEAS. The Shirmans are continuing to de-risk their innovation and aim to commercialize it in the near future.
The Built Environment
Nearly everything that humans have produced in the last 200 years has literally been built upon the backbones of prehistoric creatures that died millions of years ago and whose bodies became the fossil fuels that we use to power our factories, move our vehicles, manufacture our plastic goods, and even store our data. Finding, extracting, refining, shipping, and burning those fossil fuels releases large amounts of greenhouse gases into the atmosphere, which have been linked to changes in the global climate that have the potential to cause massive extinction, droughts, disease epidemics, and other catastrophes as the planet’s average temperature continues to climb.
Researchers at the Wyss institute are trying to kick humanity’s addiction to fossil fuels by turning to some of Nature’s humblest organisms: bacteria. “Bacteria really are the powerhouses of molecular biology research, because their genes are much easier to modify in the lab and they can grow and evolve much more quickly than other organisms,” said Core Faculty Member Pamela Silver, Ph.D., whose lab works on reprogramming bacteria and other cells to perform a variety of new functions as part of the Wyss Institute’s Living Cellular Devices Platform. Silver is also the Elliot T. and Onie H. Adams Professor of Biochemistry and Systems Biology at HMS.
One of the things Silver’s lab has been able to coax bacteria to do is eat hydrogen and carbon dioxide and excrete compounds like isopropanol, isobutanol, and isopentanol, all of which have the potential to be used as biofuels. They can also produce a compound called PHB, a precursor of biodegradable plastics. Silver recently collaborated with Daniel Nocera, Ph.D., the Patterson Rockwood Professor of Energy at Harvard University, to connect her hydrogen-hungry bacteria to his “artificial leaf” system that splits water into hydrogen and oxygen to create a “bionic leaf” that converts solar energy into chemical energy with 10% efficiency, which is far above the 1% achieved by the fastest growing plants.
Beyond biofuels, the bionic leaf system has the potential to produce many carbon-based molecules, meaning that one day we might be able to stop pulling fossil fuels out of the ground entirely and produce what we need for modern life in the lab. Because large amounts of bacteria can be grown relatively easily and cheaply, they could enable commercial-scale production of bioplastics that readily decompose after use, potentially replacing materials like styrofoam and other plastics that can remain in the environment for up to a million years. Bacteria could also allow the production of fuels in places where carbon-based life forms don’t exist – namely, outer space.
“With this system, we’ve essentially developed a way to do artificial photosynthesis and then one-upped Nature by coupling it with bacteria that can produce a wide range of chemicals that humans need, rather than spending that energy building root systems and flowers like plants do,” said Silver. “We’re very excited to continue developing our system to see what other products we can engineer bacteria to produce.”
Completely swapping fossil fuels for microbes as our major energy source will not happen overnight, so in the interim, reducing the amount of fossil fuels we use is a good strategy to try to mitigate the effects of the greenhouse gases they emit. As average global temperatures steadily climb, cooling our buildings is rapidly becoming one of the largest demands for fossil fuels – an appetite that is expected to triple by 2050. Part of the reason air conditioners are so power-hungry is because they remove moisture from humid air in addition to cooling it, and the vast majority of commercially available air conditioners achieve this through a process called mechanical vapor compression. Although cheap to manufacture, vapor compression requires a large input of energy to dehumidify air, making them inefficient and one of the largest consumers of energy in industrialized countries.
An alternative cooling method called evaporative cooling (EC) has been used by humans for millennia to cool buildings by drawing in hot outside air, passing it over water to transfer heat from the air to the water via evaporation, and releasing the cooled air inside. EC coolers use up to 75% less energy than modern vapor-compression coolers, but they only work well in relatively dry climates because they add moisture to the air as they cool it, making them less effective in humid areas.
A multidisciplinary team of scientists and designers including members of the Wyss Institute’s Adaptive Material Technologies Platform, Harvard’s Graduate School of Design (GSD), and the Harvard Center for Green Buildings and Cities (HCGBC) is developing an improved EC system that can work efficiently in hot, humid climates and could one day replace vapor-compression coolers with a much lower-energy option. Their project takes its inspiration from an unlikely source: duck feathers. Ducks and other birds are constantly exposed to the elements, but water droplets bounce right off their backs thanks in part to their very rough micro-structure.
“When a droplet touches and then leaves the surface of the feather, a small amount of heat transfer occurs. We realized that we could take advantage of this property of water-repellent surfaces to optimize how much heat is removed from the air in an EC cooling system, without causing an increase in humidity,” explained Jack Alvarenga, M.S., a Staff Scientist at the Wyss Institute and one of the co-leaders of the project.
The team’s innovation, called cold-SNAP (short for cold Superhydrophobic Nano-Architectured Process), is a rough, microscale, water-repellent material that can be easily applied to ceramic, one of the most widely available building materials in the world. By selectively applying it to only one side of a ceramic slab, the researchers can ensure that when the porous ceramic is soaked in water, the water accumulates on the uncoated side. This effectively isolates the evaporation process from the air that is being cooled, preventing it from becoming humid and making it feel cooler.
“This approach of separating humid from dry air is called indirect evaporative cooling [IEC], and there are types of coolers on the market today that use it, but they rely on multiple components and materials, making them inefficient,” said Jonathan Grinham, D.Des., a lecturer at GSD, researcher at HCGBC, and the second project co-leader. “Our system is much simpler to manufacture, doesn’t require as much maintenance, and is as efficient as we could possibly make it thanks to its multi-stage cooling elements.”
The team’s prototype system uses a 3D printer to extrude a multi-channel ceramic heat exchange structure that is then modified by adding a cold-SNAP coating on selected components, allowing cool, dry air to be kept separate from warm, moist air during the EC process. These structures could be integrated into IEC coolers and sold as environmentally friendly air conditioners in a wide variety of climate zones. In addition to manufacturing coolers, the researchers envision the construction of buildings with cold-SNAP integrated into their ceramic or brick façades, which would allow a building to effectively cool itself while only using energy to pump water through the system.
Alvarenga and Grinham, who are part of the Adaptive Living Environments (ALivE) group at Harvard as well as the Wyss Institute, are continuing to refine their cold-SNAP technology with the goal of turning it into a commercially viable product. The ALivE group is co-led by Martin Bechthold, D.Des., who is an Associate Faculty Member at the Wyss Institute and Director of the Doctor of Design program at GSD, and Allen Sayegh, M.Des., an Associate Professor at GSD.
“A lot of the innovations in materials science right now, like what the Aizenberg group at the Wyss Institute is doing, are happening at the micro- to nano-scale, which is usually completely outside the realm of the materials that designers and architects work with,” said Bechthold. “This project is a great example of how the ALivE group allows scientists and designers to bring their different modes of thinking and skills together to identify how new technologies developed in the lab can be applied to the real world, and cold-SNAP in particular has the potential to significantly reduce our impact on the environment.”
“We all need to work together to bring full force to bear on the problem of sustainability if we are to save our world and protect it for generations to come,” said Wyss Institute Founding Director Donald Ingber. “And so I am very proud of how our community has begun to take on this challenge, and to leverage Nature’s own design principles to help find meaningful and impactful solutions.”