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[Michaelangelica]

Not sure if I approve of this
An award for someone who makes PLASTIC TREES!

Naturally Inspired

By Kenny Berkowitz '81

Abe Stroock examines his “synthetic tree,” which mimics transpiration in plants.
University Photo

Searching for inspiration on a walk through Northern California’s Redwood National Park, Abraham Stroock stopped to look around him. But it wasn’t the physical beauty of the giant sequoias that left him transfixed; it was the beauty of the physics that allows these trees to transport water hundreds of feet in the air, pushing against gravity for a thousand years without expending any biological energy. And though Stroock continues to find his inspiration in nature, the thing that currently excites him is a small piece of polymer no bigger than a stick of gum.

“I’m not a naturalist, so the wonder of life doesn’t come as easily to me as the physical reality of it,” says Stroock, assistant professor of chemical and biomolecular engineering, as he slides his latest “synthetic tree” out of its plastic sandwich bag. “I wouldn’t have pursued this for the last five years, trying to get this to work, if there wasn’t good evidence that plants do this. If we hadn’t studied the physiology of plants, we wouldn’t have had the courage to launch into this project.”

With three days left of spring classes, as the trees on the quad come into full bloom, Stroock holds his synthetic tree up to the window, catching the sunlight in its two small circles etched side by side. After numerous attempts to build porous structures that could replicate the capillary action that gets sap to the highest twig—all unsuccessful—Stroock and his graduate student, Tobias Wheeler, abandoned conventional wisdom and devised a new concept: Instead of thinking of the leaf material that pulls the water to the top of the trees as porous material, like filter paper, they imagined it might be more like a gel, which can hold water at the molecular scale. That would explain why a leaf can remain water-filled even in extremely dry conditions. The polymeric tree in his hand, capable of wicking microscopic amounts of water at very great tension through its photo-lithographed channels, is the result of that breakthrough.

It’s been a long road, but with their work recently published in Nature, Stroock and Wheeler know they are on to something. “We flailed around for two or three years, unsure of what path to take,” says Wheeler, Stroock’s first graduate student, who completed his doctorate in May 2008. “No one had ever tried to tackle this problem before, and for a while it felt like we weren’t making any progress, which was tough. But once we switched from capillaries to this polymeric material, we had the first inklings this approach could in fact work. Things started to fall in place, and we wound up reaching the goal we’d set for ourselves five years earlier.”

If Stroock and Wheeler are right, the implications are enormous. The fundamental challenge—to engineer nanoscaled materials that reproduce the processes of living cells—is even more difficult than it sounds, and these trees represent the first synthetic system to mimic transpiration in plants, pumping water with enough power to reach the top of a giant sequoia.


In one of its narrowest applications, a collaboration with Alan Lakso of the New York State Agricultural Experiment Station in Geneva, this technology could be used to measure water pressure inside grapevines and apple trees, providing a continuous stream of data that would allow growers to quickly adjust irrigation.

“To have a collaboration like this between a plant scientist and a chemical engineer is very unusual,” says Lakso, professor of pomology and viticulture, who sought out Stroock after reading a newspaper article about the synthetic tree. “It’s been great to brainstorm with an engineer who is fascinated by plants, because the physics of plants tends to be extremely complex, which makes them very hard to describe and even harder to model as they change over time.”

In its widest applications, this same technology could provide the foundations for a large-scale passive system for heat transfer, a microfluidic lab-on-a-chip, or an electrode for low temperature fuel cells.

“The synthetic tree is a real tour de force, but it’s just one of the things that makes Abe so extraordinary,” says Paulette Clancy, William C. Hooey Director of Chemical and Biomolecular Engineering. “It’s this sense of innovation, this incredible boldness he brings to everything he does. He’ll jump into a field that is already heavily populated, which is awfully difficult to do, and make a real impact. He brings a very thorough approach and a deep physical understanding to reach some very creative solutions—which is rare.”

In the five years since coming to Cornell, Stroock has published 16 papers covering a wide range of projects in microfluidics, which he’s balanced with a teaching load of both undergraduate and graduate courses, winning a College of Engineering Excellence in Teaching Award in 2006.

“With Abe, we have somebody trained as a physicist, who teaches chemical engineering courses so well that he wins awards for teaching,” says Clancy. “He took a standard course in heat and mass transfer, which is typically about the effects that come into play when you scale up to a large industrial process, and turned that on its head, asking ‘What happens when you scale it down to microscopic length? What additional factors do you need to take into account?’ That’s the kind of innovative approach that really benefits our students. Even now, during his tenure year, when most academics would be concerned with themselves, he’s been taking time to lobby for daycare facilities on campus, and I think that kind of selflessness speaks volumes about who he is as a person.”

Stroock started exploring the world as child, growing up outside Boulder, Colo., as the son of a mathematician and an early childhood educator. (His father, Daniel, is an MIT professor best known for his work in diffusion processes; his mother, Lucy, is currently on the adjunct faculty of the Urban College of Boston.) When he was a teenager, the family moved to Cambridge, Mass., where his father began teaching at MIT and Stroock began his undergraduate career. Two years later, he transferred to Cornell, where he graduated cum laude in 1995 with a bachelor’s degree in physics.

Unsure of what to do next, Stroock moved to France, where he had lived as a high school exchange student with the family of Laure Mougeot, who has since become his wife. After receiving a master’s degree in solid state physics from the University of Paris—and getting married—Stroock returned to Cambridge, completing his Ph.D. in chemical physics from Harvard in 2002 while Laure began writing case studies for the Harvard Business School. Then, after his Ph.D. and a brief post-doc with Harvard’s George Whitesides, who Clancy calls “the world’s preeminent expert on microfluidics,” Stroock returned to Cornell as an assistant professor, where he met the newly arrived Wheeler.



The microscope image (above) shows water-filled, spherical voids within the hydrogel that plays the key role in the leaf and root of the synthetic tree. These water capsules serve as miniature laboratories for studying the properties of water at large negative pressures (down to -220 atmospheres).
Tobias Wheeler
“The first summer I worked with him, he came to the lab almost every day,” says Wheeler. “That says a lot about his approach, which has always felt very collaborative, very cooperative. My first impression was that he looked very young, and when we initially began meeting people to talk about the synthetic tree, they thought he was a graduate student and I was his undergraduate assistant. We were amused, but it’s easy to see how people might have thought that, because he’s so enthusiastic and open to new ideas. And that energy carried through my Ph.D., recharging me whenever we encountered a barrier in our research.”


In a second, equally ambitious microfluidics project, Stroock is collaborating with researchers at Weill Cornell Medical College to develop a biodegradable bandage to transport fluid to and from a wound; and in a third, he’s collaborating with Professor Lawrence Bonassar to engineer scaffolded, tissue-like, functional materials that could be used to either foster the growth of healthy cells for transplantation or restrict the growth of tumors.


“At its core, we want to make a device that can mimic the way the body delivers nutrients to its tissues,” says Bonassar, associate professor of biomedical engineering with a joint appointment in mechanical engineering. “Tissues contain within themselves a network of channels—blood vessels—through which they get nutrients. What we did was to take this basic architectural feature of the body and superimpose it on a hydrogel, which is mostly water and polysaccharide, to make a better tool for culturing cells. It’s a material that has a long history in medicine, but we’re using it in an entirely new application.

“Abe has this wonderful combination of precision, creativity, and relentlessness,” continues Bonassar. “We both knew very quickly that we had something special, and when you have lightning in a bottle, there’s a temptation to share it as quickly as possible. But Abe was always very focused on the task at hand. He was the one who kept saying, ‘We just need one more experiment to nail this down.’ And as one turned into two, then ten, he kept going until he was 100 percent certain of what we had. In many ways, Abe is the kind of person I came to Cornell to work with: someone who would challenge me, send me in new directions, and do things no one had ever done before.”

Taken together, the projects have earned Stroock a National Science Foundation Career Award, a 3M non-tenured faculty grant, an Arnold and Mabel Beckman Foundation Young Investigator grant, participation in the Frontiers of Engineering Symposium at the National Academy of Engineering, and membership in Technology Review’s 2007 list of 35 top innovators under 35 years old. And for all their differences, the three projects share a common root in plant science, biomimicry, and fluid mechanics.

Cornell Engineering : Naturally Inspired
I have quoted much of the article as it seems more of a press release.
More here

Synthetic tree: A means to remove CO2 from the air
Wednesday, September 24, 2008, 18:00
This news item was posted in Science category and has 1 Comment so far.


In 2003, a Dr. Klaus Lackner, a Columbia University physicist, had designed a synthetic tree that could draw carbon dioxide from air and retain the carbon. It was the first step in application of carbon sequestration technology.


However, Dr. Lackner’s synthetic tree did not look like a tree or perform any of the functions of a real tree. The synthetic tree was merely an air capture device to remove carbon from the atmosphere and store it.

Now, in September 2008, Abraham Stroock and Tobias Wheeler, of Cornell university, have created a synthetic tree that simulates the process of transpiration by which trees draw water to its branches and leaves.

What are synthetic trees?
A synthetic tree is a palm-sized microfluidic system that mimics the main features of transpiration. In synthetic trees, evaporation or transduction of water in the vapour phase into negative pressures in the liquid phase, takes place followed by stabilization and flow of liquid water at very high negative pressures.
A real tree can transfer water to great heights, up to 85 meters tall, from the roots to its leaves, through its trunk. The synthetic trees, created by Stroock and Tobias Wheeler, can transfer liquids in a similar way to amazing heights.

The synthetic tree comprises two networks of parallel channels placed next to each other in a thin sheet of hydrogel - a material used to make contact lenses - connected to a main channel, thus replicating a tree’s vascular system.

In an synthetic tree, the tranparent sheet of hydrogel is 1 millimeter thick. There are 80 parallel channels etched into the hydrogel sheet. These parallel sheets are connected to a main channel that enters into a network of microchannels in the leaf or root network. The channels, in a synthetic tree are approximately 100 micrometers wide.

How do synthetic trees work?
Real trees use xylem, a tubular tissue-like substance, to pull water out of the ground and pass it to the leaves.

Because of negative pressure, the water remains in a metastable state, something between a liquid and vapor.

For their synthetic tree, Stroock and Wheeler decided to use hydrogel, or polyhydroxyethyl methacrylate, to replicate the plant membrane. Hydrogel is a porous solid with the mixture of the solid and liquid phase at the molecular level. This makes the pores very tiny - much less than the maximum allowable 10 nanometers to hold the water - so that the negative pressure is high enough to suck the water. If the pores are larger than 10 nanometers, then the pores will fail to hold on to the liquid.

Synthetic trees to remove CO2 from air, carbon extraction and synthetic tree technology for environment and air cleaning | DWS Tech

ISTM that the most interesting thing about this is the low energy pumping of water.
Part of the problem with water scarcity is getting it to where it is needed (Demonstarted last week in Oz wher 1/2metre of rain fell on the coast (in one day!) and the inland and Murry Darling & W. Victoria is still in drought)