Professor of materials science and engineering to lead MIT’s research enterprise in Singapore.
Eugene A. Fitzgerald, the Merton C. Flemings-Singapore MIT Alliance Professor of Materials Engineering at MIT, has been appointed chief executive officer and director of the Singapore-MIT Alliance for Research and Technology (SMART).
Eugene A. Fitzgerald

Eugene A. Fitzgerald, the Merton C. Flemings-Singapore MIT Alliance Professor of Materials Science and Engineering at MIT, has been appointed chief executive officer and director of the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore established in partnership with the National Research Foundation of Singapore. He is also the lead principal investigator of the SMART Low Energy Electronic Systems Interdisciplinary Research Group. He replaces Daniel Hastings, the Cecil and Ida Green Education Professor, who returns to MIT to head the Department of Aeronautics and Astronautics. Hastings served as SMART CEO and director from 2014 to 2018.

Fitzgerald has a distinguished career as an academic, researcher, and serial entrepreneur and has a keen awareness on innovation. He started his career as a research scientist in AT&T Bell Labs in 1989 upon attaining his PhD in materials science and engineering from Cornell University and a BS degree in materials science and engineering from MIT. Leveraging his experience at AT&T Bell Labs, he and colleagues invented high mobility strained silicon and commercialized the technology through AmberWave System Corporation — a company he co-founded in 1998 with his former MIT graduate student Mayank Bulsara. The majority of silicon integrated circuits in cell phones, computers, and other applications use the technology today.

Since 2004, he also founded or co-founded six other enterprises in the areas of semiconductors, water purification, and silicon-based high efficiency multi-junction solar cells.

Fitzgerald is the co-author of the book “Inside Real Innovation,” which promotes innovation as an iterative process where one goes through several cycles in the areas of technology, market, and implementation. In 2008 he co-founded a not-for-profit entity that formed joint corporate-university innovation teams to help corporations find new directions as well as educate participants through early-stage real-world project exploration.

“Professor Fitzgerald is an experienced academic leader and an accomplished innovator and entrepreneur. He is well-regarded in both the research and enterprise spheres in Singapore. I am confident that he will carry on the excellent leadership and propel SMART into the next phase of growth,” says MIT Provost Martin Schmidt. 

SMART unites faculty, researchers, and graduate students from MIT and Singapore with academic and industry researchers in Singapore and Asia to collaborate in new areas of science and technology, and propel innovations into the enterprise space.

Fitzgerald says: “Having been involved with MIT programs in Singapore from the start in 1998, I have seen MIT and Singapore evolve together through collaboration in research, innovation, and enterprise, and look forward to building more capabilities and success in all areas.”

SMART comprises five large-scale research programs plus the Innovation Center. These programs are: Antimicrobial Resistance, BioSystems and Micromechanics, Disruptive and Sustainable Technologies for Agricultural Precision, Future Urban Mobility, and Low Energy Electronic Systems.

back to newsletter– Singapore-MIT Alliance for Research and Technology | MIT News Office
February 6, 2019

 

Expert in high-efficiency energy and water systems will succeed Gang Chen as MechE department head.
MIT evelyn wang meche A1 Vickmark
Evelyn Wang. Photo, Bryce Vickmark.

Evelyn Wang, the Gail E. Kendall [1978] Professor and director of MIT’s Device Research Laboratory, has been named head of the MIT Department of Mechanical Engineering, effective July 1.

“Professor Wang’s accomplishments as a researcher and as an educator have been remarkable,” says Anantha Chandrakasan, dean of the School of Engineering. “I am very pleased she has agreed to take on this role for Course 2. She is a true community builder and will do great things for the department. I look forward to her leadership and her input on the School of Engineering’s future.”

An internationally recognized leader in phase change heat transfer on nanostructure surfaces, Wang’s research focuses on high-efficiency energy and water systems. Her work on solar cells that convert heat into focused beams of light was named as one of MIT Technology Review’s 10 breakthrough technologies of 2017. Her work on the development of a device that can extract fresh water from the air in arid environments was selected by Scientific American and the World Economic Forum as one of 2017’s 10 promising emerging technologies.  

Currently the associate department head for operations in MechE, Wang has served as co-chair of the department’s strategic planning committee and the MechE-Lincoln Laboratory Task Force. She has taught and mentored hundreds of Course 2 students; more than 10 of her former graduate students and postdocs currently serve as faculty members at various institutions. 

Wang received a DARPA Young Faculty Award in 2008, an Air Force Office of Scientific Research Young Investigator Award in 2011, the American Society of Mechanical Engineers Bergles-Rohsenow Young Investigator Award in Heat Transfer in 2012, and she was honored by the Office of Naval Research Young Investigator Program Award in 2012. Wang is also a 2016 recipient of the ASME Electronic and Photonic Packaging Division Women Engineer Award; in 2017 she won the ASME Gustus Larson Memorial Award and the MIT Bose Award, and was named one of Foreign Policy’s “Global ReThinkers.” Wang is also an ASME Fellow and has 20 filed or pending patents.

Wang received her bachelor’s degree in mechnical engineering from MIT in 2000, and MS and PhD degrees from Stanford University in 2001 and 2006, respectively.

She will replace Gang Chen, the Carl Richard Soderberg Professor in Power Engineering, who has been department head since July 1, 2013. “I am thankful for Gang’s tremendous leadership in MechE,” Chandrakasan noted. “He has hired amazing new faculty members, deftly managed the challenges of huge growth in Course 2 enrollments, and been a key leader in securing support for students and faculty, as well as for spaces that will allow for continued cutting-edge research and other activities that make MechE such a distinctive community.”

back to newsletterSchool of Engineering
MIT News | June 22, 2018

 

Tuesday, 20 November 2018 10:15

Explaining the plummeting cost of solar power

Researchers uncover the factors that have caused photovoltaic module costs to drop by 99 percent.

David L. Chandler | MIT News Office
November 20, 2018

The dramatic drop in the cost of solar photovoltaic (PV) modules, which has fallen by 99 percent over the last four decades, is often touted as a major success story for renewable energy technology. But one question has never been fully addressed: What exactly accounts for that stunning drop?

 MIT Solar Pricing 0
Photos show a solar installation from 1988 (left) and a present-day version. Though the basic underlying technology is the same, a variety of factors have contributed to a hundredfold decline in costs. Now, researchers have identified the relative importance of these different factors.

A new analysis by MIT researchers has pinpointed what caused the savings, including the policies and technology changes that mattered most. For example, they found that government policy to help grow markets around the world played a critical role in reducing this technology’s costs. At the device level, the dominant factor was an increase in “conversion efficiency,” or the amount of power generated from a given amount of sunlight.

The insights can help to inform future policies and evaluate whether similar improvements can be achieved in other technologies. The findings are being reported today in the journal Energy Policy, in a paper by MIT Associate Professor Jessika Trancik, postdoc Goksin Kavlak, and research scientist James McNerney.

The team looked at the technology-level (“low-level”) factors that have affected cost by changing the modules and manufacturing process. Solar cell technology has improved greatly; for example, the cells have become much more efficient at converting sunlight to electricity. Factors like this, Trancik explains, fall in a category of low-level mechanisms that deal with the physical products themselves.

The team also estimated the cost impacts of “high-level” mechanisms, including learning by doing, research and development, and economies of scale. Examples include the way improved production processes have cut the number of defective cells produced and thus improved yields, and the fact that much larger factories have led to significant economies of scale.

The study, which covered the years 1980 to 2012 (during which module costs fell by 97 percent), found that there were six low-level factors that accounted for more than 10 percent each of the overall drop in costs, and four of those factors accounted for at least 15 percent each. The results point to “the importance of having many different ‘knobs’ to turn, to achieve a steady decline in cost,” Trancik says. The more different opportunities there are to reduce costs, the less likely it is that they will be exhausted quickly.

The relative importance of the factors has changed over time, the study shows. In earlier years, research and development was the dominant cost-reducing high-level mechanism, through improvements to the devices themselves and to manufacturing methods. For about the last decade, however, the largest single high-level factor in the continuing cost decline has been economies of scale, as solar-cell and module manufacturing plants have become ever larger.

“This raises the question of which factors can help continue the cost decline,” Trancik says. “What are the limits to the size of the plants?”

In terms of government policy, Trancik says, policies that stimulated market growth accounted for about 60 percent of the overall cost decline, so “that played an important part in reducing costs.” Policies stimulating market growth globally included measures such as renewable portfolio standards, feed-in tariffs, and a variety of subsidies. Government-funded research and development in various nations accounted for the other 40 percent — although public R&D played a larger part in the earlier years, she says.

This is important information, she adds, because “for a long time there has been a debate about whether these policies work — were they really driving technological improvement? Now, we can not only answer that question, we can say by how much.”

This finding, which is based on modeling device-level mechanisms rather than purely correlational analysis, provides strong evidence of a “virtuous cycle” that can be created between technology innovation and policies to reduce emissions, Trancik says. As emissions policies are implemented, low-carbon technology markets grow, technologies improve, and the costs of future emissions reductions can decline. “This analysis helps us understand why this happens, and how strong the feedbacks can be.”

Trancik and her co-workers plan to apply similar methodology to analyzing other technologies, such as nuclear power, as well as the other parts of solar installations — the so-called balance of systems, including the mounting structures and power controllers needed for the solar modules — which were not included in this study. “The method we developed can be used as a tool to assess costs of different technologies, both retrospectively and prospectively,” Kavlak says.

“This opens up a different way of modeling technological change, from the device level all the way up to policy measures, and everything in between,” Trancik says. “We’re opening up the black box of technological innovation.”

“Going forward, we can improve our intuition about what factors in general make technologies improve quickly. The application of this tool to solar PV is just the beginning of what we can do,” McNerney says.

While the study focused on past performance, the factors it identified suggest that “it does look like there are opportunities for further cost improvements with this technology.” The findings also suggest that researchers should continue working on alternative technologies to crystalline silicon, which is the dominant form of solar photovoltaic technology today, but many other varieties are being actively explored with potentially higher efficiencies or lower materials costs.

The study also highlights the importance of continuing the progress in improving the efficiency of the manufacturing systems, whose role in driving down costs has been important. “There are likely more gains to be had in this direction,” Trancik says.

Gregory Nemet, a professor of public affairs at the University of Wisconsin at Madison, who was not involved in the study, says, “This work is important in that it identifies that the growth in demand for solar PV in the past 15 years was the most important driver of the astounding cost reductions over that period. Policies in Japan, Germany, Spain, California, and China drove the growth of the market and created opportunities for automation, scale, and learning by doing.”

Nemet adds, “Their model is simple and general, which could make it useful for designing policies for other technologies that will be needed to address climate change and other energy-related problems.”

The research was supported by the U.S. Department of Energy.

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MIT researchers create predictable patterns from unpredictable carbon nanotubes.

Integrating nanoscale fibers such as carbon nanotubes (CNTs) into commercial applications, from coatings for aircraft wings to heat sinks for mobile computing, requires them to be produced in large scale and at low cost. Chemical vapor deposition is a promising approach to manufacture CNTs in the needed scales, but it produces CNTs that are too sparse and compliant for most applications. Applying and evaporating a few drops of a liquid such as acetone to the CNTs is an easy, cost-effective method to more tightly pack them together and increase their stiffness, but until now, there was no way to forecast the geometry of these CNT cells.

MIT researchers have now developed a systematic method to predict the two-dimensional patterns CNT arrays form after they are packed together, or densified, by evaporating drops of either acetone or ethanol. CNT cell size and wall stiffness grow proportionally with cell height, they report in a Communication in the Feb. 14, 2018, issue of Physical Chemistry Chemical Physics [PCCP].

One way to think of this CNT behavior is to imagine how entangled fibers such as wet hair or spaghetti collectively reinforce each other. The larger this entangled region is, the higher its resistance to bending will be. Similarly, longer CNTs can better reinforce one another in a cell wall. The researchers also find that CNT binding strength to the base on which they are produced, in this case, silicon, makes an important contribution to predicting the cellular patterns that these CNTs will form.

“These findings are directly applicable to industry because when you use CVD, you get nanotubes that have curvature, randomness and are wavy, and there is a great need for a method that can easily mitigate these defects without breaking the bank,” AeroAstro Postdoc Itai Y. Stein [SM '13, PhD '16] says. Co-authors include materials science and engineering graduate student Ashley L. Kaiser, MechE Postdoc Kehang Cui, and senior author Brian L. Wardle, Professor of Aeronautics and Astronautics.

“From our previous work on aligned carbon nanotubes (CNTs) and their composites, we learned that more tightly packing the CNTs is a highly effective way to engineer their properties,” Wardle says. “The challenging part is to develop a facile way of doing this at scales that are relevant to commercial aircraft (100’s of meters), and the predictive capabilities that we developed here are a large step in that direction."

Detailed measurements

Carbon nanotubes are highly desirable because of their thermal, electrical, and mechanical properties, which are directionally dependent. Earlier work in Wardle’s lab demonstrated that waviness reduces the stiffness of CNT arrays by as little as 100 times, and up to 100,000 times. The technical term for this stiffness, or ability to bend without breaking, is elastic modulus. Carbon nanotubes are from 1,000 to 10,000 times longer than they are thick, so they deform principally along their length.

For an earlier Applied Physics Letters paper, Stein and colleagues used nanoindentation techniques to measure stiffness of aligned carbon nanotube arrays and found them to be 1,000 to 10,000 times less stiff than the theoretical stiffness of individual carbon nanotubes. Stein, Wardle and former visiting MIT graduate student Hülya Cebeci also developed a theoretical model explaining changes at different packing densities of the nanofibers. [Cebeci is now a professor of aerospace engineering at Istanbul Technical University.]

The new work shows that CNTs compacted by the capillary forces from first wetting them with acetone or ethanol and then evaporating the liquid also produces CNTs that are 100s to 1000s of times less stiff than expected by theoretical values. This capillary effect, known as elastocapillarity, is similar to a how a sponge often dries into a more compact shape after being wetted and then dried.

“Our findings all point to the fact that the CNT wall modulus is much lower than the normally assumed value for perfect CNTs because the underlying CNTs are not straight. Our calculations show that the CNT wall is at least two orders of magnitude less stiff than we expect for straight CNTs, so we can conclude that the CNTs must be wavy,” Stein says.

Heat adds strength

The researchers used a heating technique to increase the adhesion of their original, undensified CNT arrays to their silicon wafer substrate. CNTs densified after heat treatment were about four times harder to separate from the silicon base than untreated CNTs. Kaiser and Stein, who share first authorship of the paper, are currently developing an analytical model to describe this phenomenon and tune the adhesion force, which would further enable prediction and control of such structures.

“Many applications of vertically aligned carbon nanotubes (VACNTs), such as electrical interconnects, require much denser arrays of nanotubes than what is typically obtained for as-grown VACNTs synthesized by chemical vapor deposition (CVD),” says Mostafa Bedewy, assistant professor at the University of Pittsburgh, who was not involved in this work. “Hence, methods for post-growth densification, such as those based on leveraging elastocapillarity have previously been shown to create interesting densified CNT structures. However, there is still a need for a better quantitative understanding of the factors that govern cell formation in densified large-area arrays of VACNTs. The new study by the authors contributes to addressing this need by providing experimental results, coupled with modeling insights, correlating parameters such as VACNT height and VACNT-substrate adhesion to the resulting cellular morphology after densification.”

“There are still remaining questions about how the spatial variation of CNT density, tortuosity [twist], and diameter distribution across the VACNT height affects the capillary densification process, especially that vertical gradients of these features can be different when comparing two VACNT arrays having different heights,” Bedewy notes. “Further work incorporating spatial mapping of internal VACNT morphology would be illuminating, although it will be challenging as it requires combining a suite of characterization techniques.”

The variety of length scales and physical and chemical mechanisms present in carbon nanotubes and other nanoscale materials makes it easy to either oversimplify or to focus on the wrong mechanism, Stein cautions. “Our current predictive capabilities from this paper are very useful, because we give other researchers in the field a pragmatic solution for how they could at least get some predictability, so that they can accelerate their materials design process, and have a working prototype sooner,” Stein says. “In the meantime, while other groups can utilize this new information, which is the best we can do given our current data, we are going to work on collecting a richer dataset that will allow us to investigate the underlying mechanisms and thereby enable even better prediction in the future,” he adds.

Picturesque patterns

Graduate student Kaiser, who was a 2016 MIT Summer Scholar, analyzed the densified CNT arrays with scanning electron microscopy [SEM] in the MIT Materials Research Laboratory’s NSF-MRSEC supported Shared Experimental Facilities. While gently applying liquid to the CNT arrays in this study caused them to densify into predictable cells, vigorously immersing the CNTs in liquid imparts much stronger forces to them, forming randomly shaped CNT networks. “When we first started exploring densification methods, I found that this forceful technique densified our CNT arrays into highly unpredictable and interesting patterns. As seen optically and via SEM, these patterns often resembled animals, faces, and even a heart – it was a bit like searching for shapes in the clouds,” Kaiser says. A colorized version of her optical image showing a CNT heart is featured on the cover of the Feb. 14, 2018, print edition of Physical Chemistry Chemical Physics, which coincides with Valentine’s Day.

“I think there is an underlying beauty in this nanofiber self-assembly and densification process, in addition to its practical applications,” Kaiser adds. “The CNTs densify so easily and quickly into patterns after simply being wet by a liquid. Being able to accurately quantify this behavior is exciting, as it may enable the design and manufacture of scalable nanomaterials.”

The ultimate goal of this research is to be able to precisely predict the post-processing nanofiber pattern beforehand, Kaiser says. “When we have a specific end-goal structure in mind, such as this cellular pattern, we’d like to be able to accurately design its geometry based on our process,” Kaiser says. “With that capability, this liquid-based densification technique could be used to create large-scale nanofiber systems for a wide range of applications.”

This work made use of the MIT Materials Research Laboratory Shared Experimental Facilities, which are supported in part by the MRSEC Program of the National Science Foundation, and MIT Microsystems Technology Laboratories. This research was supported in part by Airbus, ANSYS, Embraer, Lockheed Martin, Saab AB, Saertex, and TohoTenax through MIT's Nano-Engineered Composite Aerospace Structures Consortium and by NASA through the Space Technology Research Institute for Ultra-Strong Composites by Computational Design.

Denis Paiste, Materials Research Laboratory
February 14, 2018
 

Method boosts differentiation of stem cells into mature blood cell types, may help leukemia and lymphoma patients.
MIT Stem Cell Mechanics PRESS Web
MIT engineers grew these mesenchymal stem cells (red, with blue nuclei) on a surface with mechanical properties similar to those of bone marrow. Image, Frances Liu and Krystyn Van Vliet.

Patients with blood cancers such as leukemia and lymphoma are often treated by irradiating their bone marrow to destroy the diseased cells. After the treatment, patients are vulnerable to infection and fatigue until new blood cells grow back.

MIT researchers have now devised a way to help blood cells regenerate faster. Their method involves stimulating a particular type of stem cell to secrete growth factors that help precursor cells differentiate into mature blood cells.

Using a technique known as mechanopriming, the researchers grew mesenchymal stem cells (MSCs) on a surface whose mechanical properties are very similar to that of bone marrow. This induced the cells to produce special factors that help hematopoietic stem and progenitor cells (HSPCs) differentiate into red and white blood cells, as well as platelets and other blood cells.

“You can think about it like you’re trying to grow a plant,” says Krystyn Van Vliet, the Michael and Sonja Koerner Professor of Materials Science and Engineering, a professor of biological engineering, and associate provost. “The MSCs are coming in and improving the soil so that the progenitor cells can start proliferating and differentiating into the blood cell lineages that you need to survive.”

In a study of mice, the researchers showed that the specially grown MSCs helped the animals to recover much more quickly from bone marrow irradiation.

Van Vliet is the senior author of the study, which appears in the Oct. 24 issue of the journal Stem Cell Research and Therapy. The paper’s lead author is recent MIT PhD recipient Frances Liu. Other authors are Singapore-MIT Alliance for Research and Technology (SMART) postdoc Kimberley Tam, recent MIT PhD recipient Novalia Pishesha, and former SMART postdoc Zhiyong Poon, now at Singapore General Hospital.

Cellular drug factories

MSCs are produced throughout the body and can differentiate into a variety of tissues, including bone, cartilage, muscle, and fat. They can also secrete proteins that help other types of stem cells differentiate into mature cells.

“They act like drug factories,” Van Vliet says. “They can become tissue lineage cells, but they also pump out a lot of factors that change the environment that the hematopoietic stem cells are operating in.”

When cancer patients receive a stem cell transplant, they usually receive only HPSCs, which can become blood cells. Van Vliet’s team has shown previously that when mice are also given MSCs, they recover faster. However, in a given population of MSCs, usually only about 20 percent produce the factors that are needed to stimulate blood cell growth and bone marrow recovery.

“Left to their own devices in the current state-of-the-art culture environments, MSCs become heterogeneous and they all express a variety of factors,” Van Vliet says.

In an earlier study, Van Vliet and her SMART colleagues showed that she could sort MSCs with a special microfluidic device that can identify the 20 percent that promote blood cell growth. However, she and her students wanted to improve on that by finding a way to stimulate an entire population of MSCs to produce the necessary factors.

To do that, they first had to discover which factors were the most important. They showed that while many factors contribute to blood cell differentiation, secretion of a protein called osteopontin was most highly correlated with better survival rates in mice treated with MSCs.

The researchers then explored the idea of “mechanopriming” the cells so that they would produce more of the necessary factors. Over the past decade, Van Vliet and other researchers have shown that varying the mechanical properties of surfaces on which stem cells are grown can affect their differentiation into mature cell types. However, in this study, for the first time, she showed that mechanical properties can also affect the factors that stem cells secrete before committing to a specific tissue cell lineage.

Usually, stem cells removed from the body are grown on a flat sheet of glass or stiff plastic. The MIT team decided to try growing the cells on a polymer called PDMS and to vary its mechanical properties to see how that would affect the cells. They designed materials that varied in both their stiffness and their viscosity, which is a measure of how quickly the material stretches when stress is applied.

The researchers found that MSCs grown on materials with mechanical properties most similar to that of bone marrow produced the greatest number of the factors necessary to induce HSPCs to differentiate into mature blood cells.

Better recovery

The researchers then tested their specially grown MSCs by implanting them into mice that had had their bone marrow irradiated. Even though they did not implant any HSPCs, this treatment quickly repopulated the animals’ blood cells and helped them to recover more quickly than mice treated with MSCs grown on traditional glass surfaces. They also recovered faster than mice treated with the factor-producing MSCs that were selected by the microfluidic sorting device.

“The mouse studies were models of radiation therapy commonly used to kill cancer cells in the clinic. However, these therapies are highly destructive and also destroy healthy cells as well,” Liu says. “Our mechanoprimed MSCs can help to better support and regenerate those healthy bone marrow cells faster in these mouse models, and we hope the same results would translate to humans.”

“Illustrating how mechanopriming of mesenchymal stem cells can be exploited to improve on hematopoietic recovery is of huge medical significance,” says Viola Vogel, chair of the Department of Health Science and Technology at ETH Zurich, who was not involved in the research. “It also sheds light onto how to utilize their approach to perhaps take advantage of other cell subpopulations for therapeutic applications in the future.”

Van Vliet’s lab is now performing more animal studies in hopes of developing a combination treatment of MSCs and HSPCs that could be tested in humans.

“You can’t survive with a low blood cell count for very long,” she says. “If you’re able to get your complete blood cell count up to normal levels faster, you have a much better prognosis for speed of recovery.”

The researchers also hope to study whether mechanopriming can induce MSCs to produce different factors that would stimulate the development of additional cell types that could be useful for treating other diseases.

“You could imagine that by changing their culture environment, including their mechanical environment, MSCs could be used for administration to target several other diseases,” such as Parkinson’s disease, rheumatoid arthritis, and others, Van Vliet says.

The research was funded by the BioSystems and Micromechanics Interdisciplinary Research Group of the Singapore-MIT Alliance for Research and Technology (SMART), through the Singapore National Research Foundation, and the National Institutes of Health.

back to newsletterAnne Trafton | MIT News Office
October 24, 2018 

The incubator’s winding journey to success helped its startup community grow closer while addressing environmental challenges.

Greentown Labs is the largest clean technology incubator in North America, a fact that’s easy to accept when you walk inside. The massive, open entrance of Greentown’s Somerville, Massachusetts, headquarters gives visitors the impression they’ve entered the office of one of Greater Boston’s most successful tech companies.

North America's largest clean technology incubator

Beyond the modern entryway are smaller working spaces — some cluttered with startup prototypes, others lined with orderly lab equipment — to enable foundational, company-building experiments.

In addition to the space and equipment, Greentown offers startups equity-free legal, information technology, marketing, and sales support, and a coveted network of corporations and industry investors.

But what many entrepreneurs say they like most about Greentown is the people.

“Greentown offers a lot of different things, but first and foremost among them is a community of entrepreneurs who are striving to solve big challenges in climate, energy, and the environment,” says Greentown Labs CEO Emily Reichert MBA ’12.

Greentown is full of stories of peers bumping into each other in the kitchen only to find they’re struggling with similar problems or, even better, that one of them already grappled with the problem and found a solution.

MIT has played a pivotal role in Greentown’s success since its inception. Reichert estimates about 60 percent of Greentown’s more than 90 current startups were founded by MIT alumni.

The current version of Greentown looks like the result of some well-funded, grand vision set forth long ago. But Greentown’s rise was every bit as spontaneous — and tenuous — as the early days of any startup.

A space for building

In 2010, Sorin Grama SM ’07 and Sam White were looking for office space to work on a new chiller design for their startup, Promethean Power Systems, which still develops off-grid refrigeration systems in India. They needed a place to build the big, leaky refrigeration prototypes they’d thought up. It also needed to be close to MIT, where the company founders connected with advisors and interns.

Eventually, White found “a dilapidated warehouse” on Charles Street in Cambridge for the right price. What the space lacked in beauty it made up for in size, so the founders decided to use an MIT email list to see if other founders would like to join them. Some founders building an app were first to respond. Their first reaction was to ask White and Grama to clean up a bit, and they were politely shown the door.

Without exactly intending to, Grama and White had made their warehouse a builder space. Over the next week, a few more founders came in, including Jason Hanna, the co-founder of building efficiency company Embue; Jeremy Pitts SM ’10, MBA ’10, who was creating more efficient compressor systems for the oil and gas industry as the founder of Oscomp Systems; and Adam Rein MBA ’10 and Ben Glass ’07 SM ’10, whose company Altaeros was building airborne wind turbines. The warehouse looked perfect to them.

“What we all had in common was we just needed a space to prototype and build stuff, where we could spill stuff, make noise, and share tools,” Grama says. “Pretty quickly it became a nice band of startups that appreciated the same thing.”

The winter of 2010-2011 was a freezing one in the warehouse, made worse by icy cement floors, but the founders couldn’t help but notice the benefits of working together. Any time an intern or investor came to see one company, they were introduced to the others. Founders with expertise in areas like grant writing or funding rounds would give lunchtime presentations to help the others.

Rein remembers thinking he was in the perfect environment to succeed despite the sometimes comical dysfunction of the space. One day an official with the United States Agency for International Development (USAID) stopped by to evaluate one of the startups for a grant. The visit went well enough — until she got locked in the bathroom. The founders eventually got her out, but they didn’t think the incident boded for their chances of getting that grant.

When the landlord kicked them out of Charles Street, they found a similar space in South Boston, recruiting friends and employees to help strip wires, scrape walls, and paint over the course of a week. Rein recalls his regular duties included ordering toilet paper for the building.

The space was also twice as large as the one in Cambridge, so as Greentown’s reputation spread throughout 2011, five startups became 15, then 20.

“It really took on a life of its own,” Grama says.

Among the curious MIT students who journeyed to Greentown that year was Reichert. Having worked as a chemist for 10 years in spotless, safety-certified labs before coming to MIT, she was shocked to see the condition of Greentown.
“The first time I walked in I had two gut reactions,” Reichert says. “The first was I felt this amazing energy and passion, and kind of a buzzing. If you walk into Greentown today you still feel those things. The second was, ‘Oh my god, this place is a death trap.’”

After earning her MBA, Reichert initially helped out as a consultant at Greentown. By February of 2013, she joined Greentown to run it full time. It was a critical time for the growing co-op: White and Grama were getting ready to move to India to work on Promethean, and Hanna, who had primarily led Greentown to that point, was expecting the birth of his first child.

At the same time, real estate prices in South Boston were skyrocketing, and Greentown was again being forced to move.

Reichert, who worked as CEO without a salary for more than a year, remembers those first six months on the job as the most stressful of her life. With no money to put toward a new space, she was able to partner with the City of Somerville to secure some funding and find a new location. Reichert signed a construction contract to renovate the Somerville space before she knew where the money would come from, and began lobbying state and corporate officials for sponsorships.

She still remembers the day Greentown was to be evicted from South Boston, with everyone scrambling to clean out the cluttered warehouse and a few determined founders running one last experiment until 7 p.m. before throwing the last of the equipment in a U-Haul truck and beginning the next phase of Greentown’s journey.

Growing up

Within 15 months of the move to Somerville, Greentown’s 40,000 square feet were completely filled and Reichert began the process of expanding the headquarters. Today, Greentown’s three buildings make up more than 100,000 square feet of prototyping, office, and event space and feature a wet lab, electronics lab, and machine shop.

Since its inception, Greentown has supported more than 200 startups that have created around 2,800 jobs, many in the Boston area. The original founders still serve on Greentown’s board of directors, ensuring every dollar Greentown makes goes toward supporting startups.

Of the founding companies, only Promethean and Altaeros are still housed in Greentown, although they’re all still operating in some form.

“We probably should’ve moved out, but it’s important to work in a place you really enjoy,” Rein says of Altaeros.

Grama, meanwhile, has come full circle. After ceding the reigns of Promethean and returning from India, last year he started another company, Transaera, that’s developing efficient, environmentally friendly cooling systems based on research from MIT.

This time, it took him a lot less time to find office space.

back to newsletter– Zach Winn | MIT News Office
June 25, 2019

Thursday, 26 April 2018 10:55

How to bend and stretch a diamond

The brittle material can turn flexible when made into ultrafine needles, researchers find.
MIT Flexible Diamond
This scanning electron microscope image shows ultrafine diamond needles (cone shapes rising from bottom) being pushed on by a diamond tip (dark shape at top). These images reveal that the diamond needles can bend as much as 9 percent and still return to their original shape. Courtesy of the researchers

Diamond is well-known as the strongest of all natural materials, and with that strength comes another tightly linked property: brittleness. But now, an international team of researchers from MIT, Hong Kong, Singapore, and Korea has found that when grown in extremely tiny, needle-like shapes, diamond can bend and stretch, much like rubber, and snap back to its original shape.

The surprising finding is being reported in the journal Science, in a paper by senior author Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering; MIT postdoc Daniel Bernoulli; senior author Subra Suresh, former MIT dean of engineering and now president of Singapore’s Nanyang Technological University; graduate students Amit Banerjee and Hongti Zhang at City University of Hong Kong; and seven others from CUHK and institutions in Ulsan, South Korea.

The results, the researchers say, could open the door to a variety of diamond-based devices for applications such as sensing, data storage, actuation, biocompatible in vivo imaging, optoelectronics, and drug delivery. For example, diamond has been explored as a possible biocompatible carrier for delivering drugs into cancer cells.

The team showed that the narrow diamond needles, similar in shape to the rubber tips on the end of some toothbrushes but just a few hundred nanometers (billionths of a meter) across, could flex and stretch by as much as 9 percent without breaking, then return to their original configuration, Dao says.

Ordinary diamond in bulk form, Bernoulli says, has a limit of well below 1 percent stretch. “It was very surprising to see the amount of elastic deformation the nanoscale diamond could sustain,” he says.

“We developed a unique nanomechanical approach to precisely control and quantify the ultralarge elastic strain distributed in the nanodiamond samples,” says Yang Lu, senior co-author and associate professor of mechanical and biomedical engineering at CUHK. Putting crystalline materials such as diamond under ultralarge elastic strains, as happens when these pieces flex, can change their mechanical properties as well as thermal, optical, magnetic, electrical, electronic, and chemical reaction properties in significant ways, and could be used to design materials for specific applications through “elastic strain engineering,” the team says.

Experiment (left) and simulation (right) of a diamond nanoneedle being bent by the side surface of a diamond tip, showing ultralarge and reversible elastic deformation. Image, MIT News Office.

The team measured the bending of the diamond needles, which were grown through a chemical vapor deposition process and then etched to their final shape, by observing them in a scanning electron microscope while pressing down on the needles with a standard nanoindenter diamond tip (essentially the corner of a cube). Following the experimental tests using this system, the team did many detailed simulations to interpret the results and was able to determine precisely how much stress and strain the diamond needles could accommodate without breaking.

The researchers also developed a computer model of the nonlinear elastic deformation for the actual geometry of the diamond needle, and found that the maximum tensile strain of the nanoscale diamond was as high as 9 percent. The computer model also predicted that the corresponding maximum local stress was close to the known ideal tensile strength of diamond — i.e. the theoretical limit achievable by defect-free diamond.

When the entire diamond needle was made of one crystal, failure occurred at a tensile strain as high as 9 percent. Until this critical level was reached, the deformation could be completely reversed if the probe was retracted from the needle and the specimen was unloaded. If the tiny needle was made of many grains of diamond, the team showed that they could still achieve unusually large strains. However, the maximum strain achieved by the polycrystalline diamond needle was less than one-half that of the single crystalline diamond needle.

Yonggang Huang, a professor of civil and environmental engineering and mechanical engineering at Northwestern University, who was not involved in this research, agrees with the researchers’ assessment of the potential impact of this work. “The surprise finding of ultralarge elastic deformation in a hard and brittle material — diamond — opens up unprecedented possibilities for tuning its optical, optomechanical, magnetic, phononic, and catalytic properties through elastic strain engineering,” he says.

Huang adds “When elastic strains exceed 1 percent, significant material property changes are expected through quantum mechanical calculations. With controlled elastic strains between 0 to 9 percent in diamond, we expect to see some surprising property changes.”

The team also included Muk-Fung Yuen, Jiabin Liu, Jian Lu, Wenjun Zhang, and Yang Lu at the City University of Hong Kong; and Jichen Dong and Feng Ding at the Institute for Basic Science, in South Korea. The work was funded by the Research Grants Council of the Hong Kong Special Administrative Region, Singapore-MIT Alliance for Research and Technology (SMART), Nanyang Technological University Singapore, and the National Natural Science Foundation of China.

back to newsletter– David L. Chandler | MIT News Office
April 19, 2018

Tuesday, 28 November 2017 12:33

How to get sprayed metal coatings to stick

When spraying metal coatings, melting hurts rather than helps, MIT research reveals.
MIT Melting Bonding 01
Micrographs of a metal surface after impact by metal particles. Craters are formed due to melting of the surface from the impact. Courtesy of the researchers

When bonding two pieces of metal, either the metals must melt a bit where they meet or some molten metal must be introduced between the pieces. A solid bond then forms when the metal solidifies again. But researchers at MIT have found that in some situations, melting can actually inhibit metal bonding rather than promote it. 

The surprising and counterintuitive finding could have serious implications for the design of certain coating processes or for 3-D printing, which both require getting materials to stick together and stay that way. The research, carried out by postdocs Mostafa Hassani-Gangaraj and David Veysset and professors Keith Nelson and Christopher Schuh, was reported in two papers, in the journals Physical Review Letters and Scripta Materialia.

Schuh, who is the Danae and Vasilis Salapatas Professor of Metallurgy and head of the Department of Materials Science and Engineering, explains that one of the papers outlines “a revolutionary advance in the technology” for observing extremely high-speed interactions, while the other makes use of that high-speed imaging to reveal that melting induced by impacting particles of metal can impede bonding.

The optical setup, with a high-speed camera that uses 16 separate charged-coupled device (CCD) imaging chips and can record images in just 3 nanoseconds, was primarily developed by Veysset. The camera is so fast that it can track individual particles being sprayed onto a surface at supersonic velocities, a feat that was previously not possible. The team used this camera, which can shoot up to 300 million frames per second, to observe a spray-painting-like process similar to ones used to apply a metallic coating to surfaces in many industries.

While such processes are widely used, until now their characteristics have been determined empirically, since the process itself is so fast “you can’t see it, you can’t tell what’s happening, and no one has ever been able to watch the moment when a particle impacts and sticks,” Schuh says. As a result, there has been ongoing controversy about whether the metal particles actually melt as they strike the surface to be coated. The new technology means that now the researchers “can watch what’s happening, can study it, and can do science,” he says.

The new images make it clear that under some conditions, the particles of metal being sprayed at a surface really do melt the surface — and that, unexpectedly, prevents them from sticking. The researchers found that the particles bounce away in much less time than it takes for the surface to resolidify, so they leave the surface that is still molten.

If engineers find that a coating material isn’t bonding well, they may be inclined to increase the spray velocity or temperature in order to increase the chances of melting. However, the new results show the opposite: Melting should be avoided.

MIT Melting Bonding 02
The top row of photos shows a particle that melts the surface on impact and bounces away without sticking. The bottom row shows a similar particle that does not melt and does stick to the surface. Arrows show impact sprays that look like liquid, but are actually solid particles. Courtesy of the researchers

It turns out the best bonding happens when the impacting particles and impacted surfaces remain in a solid state but “splash” outward in a way that looks like liquid. It was “an eye-opening observation,” according to Schuh. That phenomenon “is found in a variety of these metal-processing methods,” he says. Now, it is clear that “to stick metal to metal, we need to make a splash without liquid. A solid splash sticks, and a liquid one doesn’t.” With the new ability to observe the process, Hassani-Gangaraj says, “by precise measurements, we could find the conditions needed to induce that bond.”

The findings could be relevant for processes used to coat engine components in order to reuse worn parts rather than relegating them to the scrap-metal bin. “With an old engine from a large earth-moving machine, it costs a fortune to throw it away, and it costs a fortune to melt and recast it,” Schuh says. “Instead, you can clean it off and use a spray process to renew the surface.” But that requires that the sprayed coating will remain securely bonded.

In addition to coatings, the new information could also help in the design of some metal-based additive manufacturing systems, known as 3-D printing. There, as with coatings, it is critical to make sure that one layer of the printing material adheres solidly to the previous layer.

“What this work promises is an accurate and mathematical approach” to determining the optimal conditions to ensure a solid bond, Schuh says. “It’s mathematical rather than empirical.”

The work was supported by the U.S. Army through MIT’s Institute for Soldier Nanotechnologies, the U.S. Army Research Office, and the U.S. Office of Naval Research.

back to newsletter

David L. Chandler | MIT News Office
November 22, 2017

 

Noninvasive device could benefit patients with kidney disease, congestive heart failure, or dehydration.
MIT researchers have developed a noninvasive hydration sensor that is based on the same technology as MRI, but, unlike MRI scanners, it can fit in a doctor’s office.  Lina Colucci, Andrew Hall, image.
MIT researchers have developed a noninvasive hydration sensor that is based on the same technology as MRI, but, unlike MRI scanners, it can fit in a doctor’s office. Image: Lina Colucci, Andrew Hall.

For patients with kidney failure who need dialysis, removing fluid at the correct rate and stopping at the right time is critical. This typically requires guessing how much water to remove and carefully monitoring the patient for sudden drops in blood pressure.

Currently there is no reliable, easy way to measure hydration levels in these patients, who number around half a million in the United States. However, researchers from MIT and Massachusetts General Hospital have now developed a portable sensor that can accurately measure patients’ hydration levels using a technique known as nuclear magnetic resonance (NMR) relaxometry.

Such a device could be useful for not only dialysis patients but also people with congestive heart failure, as well as athletes and elderly people who may be in danger of becoming dehydrated, says Michael Cima, the David H. Koch Professor of Engineering in MIT’s Department of Materials Science and Engineering.

“There’s a tremendous need across many different patient populations to know whether they have too much water or too little water,” says Cima, who is the senior author of the study and a member of MIT’s Koch Institute for Integrative Cancer Research. “This is a way we could measure directly, in every patient, how close they are to a normal hydration state.”

The portable device is based on the same technology as magnetic resonance imaging (MRI) scanners but can obtain measurements at a fraction of the cost of MRI, and in much less time, because there is no imaging involved.

Lina Colucci, a former graduate student in health sciences and technology, is the lead author of the paper, which appears in the July 24 issue of Science Translational Medicine. Other authors of the paper include MIT graduate student Matthew Li; MGH nephrologists Kristin Corapi, Andrew Allegretti, and Herbert Lin; MGH research fellow Xavier Vela Parada; MGH Chief of Medicine Dennis Ausiello; and Harvard Medical School assistant professor in radiology Matthew Rosen.

Hydration status

Cima began working on this project about 10 years ago, after realizing that there was a critical need for an accurate, noninvasive way to measure hydration.

Currently, the available methods are either invasive, subjective, or unreliable. Doctors most frequently assess overload (hypervolemia) by a few physical signs such as examining the size of the jugular vein, pressing on the skin, or examining the ankles where water might pool.

The MIT team decided to try a different approach, based on NMR. Cima had previously launched a company called T2 Biosystems that uses small NMR devices to diagnose bacterial infections by analyzing patient blood samples. One day, he had the idea to use the devices to try to measure water content in tissue, and a few years ago, the researchers got a grant from the MIT-MGH Strategic Partnership to do a small clinical trial for monitoring hydration. They studied both healthy controls and patients with end-stage renal disease who regularly underwent dialysis.

One of the main goals of dialysis is to remove fluid in order bring patients to their “dry weight,” which is the weight at which their fluid levels are optimized. Determining a patient’s dry weight is extremely challenging, however. Doctors currently estimate dry weight based on physical signs as well as through trial-and-error over multiple dialysis sessions.

The MIT/MGH team showed that quantitative NMR, which works by measuring a property of hydrogen atoms called T2 relaxation time, can provide much more accurate measurements. The T2 signal measures both the environment and quantity of hydrogen atoms (or water molecules) present.

“The beauty of magnetic resonance compared to other modalities for assessing hydration is that the magnetic resonance signal comes exclusively from hydrogen atoms. And most of the hydrogen atoms in the human body are found in water molecules,” Colucci says.

The researchers used their device to measure fluid volume in patients before and after they underwent dialysis. The results showed that this technique could distinguish healthy patients from those needing dialysis with just the first measurement. In addition, the measurement correctly showed dialysis patients moving closer to a normal hydration state over the course of their treatment.

Furthermore, the NMR measurements were able to detect the presence of excess fluid in the body before traditional clinical signs — such as visible fluid accumulation below the skin — were present. The sensor could be used by physicians to determine when a patient has reached their true dry weight, and this determination could be personalized at each dialysis treatment.

Better monitoring

The researchers are now planning additional clinical trials with dialysis patients. They expect that dialysis, which currently costs the United States more than $40 billion per year, would be one of the biggest applications for this technology. This kind of monitoring could also be useful for patients with congestive heart failure, which affects about 5 million people in the United States.

“The water retention issues of congestive heart failure patients are very significant,” Cima says. “Our sensor may offer the possibility of a direct measure of how close they are to a normal fluid state. This is important because identifying fluid accumulation early has been shown to reduce hospitalization, but right now there are no ways to quantify low-level fluid accumulation in the body. Our technology could potentially be used at home as a way for the care team to get that early warning.”
Sahir Kalim, a nephrologist and assistant professor of medicine at Massachusetts General Hospital, described the MIT approach as “highly novel.”

“The development of a bedside device that can accurately inform providers about how much fluid a patient should ideally have removed during their dialysis treatment would likely be one of the most significant developments in dialysis care in many years,” says Kalim, who was not involved in the study. “Colucci and colleagues have made a promising innovation that may one day yield this impact.”

In their study of the healthy control subjects, the researchers also incidentally discovered that they could detect dehydration. This could make the device useful for monitoring elderly people, who often become dehydrated because their sense of thirst lessens with age, or athletes taking part in marathons or other endurance events. The researchers are planning future clinical trials to test the potential of their technology to detect dehydration.

The research was funded by the MGH-MIT Strategic Partnership Grand Challenge, the Air Force Medical Services/Institute of Soldier Nanotechnologies, the National Science Foundation Graduate Research Fellowships Program, the National Institute of Biomedical Imaging and Bioengineering, the Koch Institute Support (core) Grant from the National Cancer Institute, and Harvard University.

back to newsletterAnne Trafton | MIT News Office 
July 24, 2019

Monday, 29 October 2018 15:28

Improving materials from the nanoscale up

Transformative new tools to probe atomic structures in action are yielding better designs for metals, solar cells and polymers.

Powerful new combinations of X-rays, electrical probes and analytical computing are yielding insights into problems as diverse as fatigue in steel and stability in solar cells.

“Fatigue in steel is a major issue; you don’t see any changes in the shape of your material, and suddenly it fails," Assistant Professor C. Cem Taşan said during the MIT MRL Materials Day Symposium on Wednesday, Oct. 10, 2018. “We are putting a lot of effort in maintenance and safety, yet still we have devastating accidents,” he said, recalling the airline incident in April 2018 when a jet engine turbine blade broke apart and shrapnel from the engine broke a plane window fatally injuring a passenger.

“The airline company basically said that component passed all the maintenance requirements. So it was checked, and they couldn’t see any kind of fatigue cracks in it,” Taşan, the Thomas B. King Career Development Professor of Metallurgy, explained. Taşan is developing new steel and other metal alloys that are safer, stronger and lighter than those currently available.

Failure in metals is a complex mix of cracks and other changes in the microstructure caused by temperature, bending, stretching, compression and other forces, but most can survive at most one of these impacts before unleashing a cascade of subtle changes that ultimately result in failure.

Design for repair

Taşan outlined progress on a vanadium-based alloy that changes back to its original state when stress is taken away, and a new type of steel that can be transformed back to its original state when heat is applied. Stress tests to measure fatigue in Taşan’s new steel showed improvement over other steels.

Underlying these findings are new nanoscale experimental techniques that Taşan employs to identify the multiple causes of failure in metal alloys. Taşan combines energy-dispersive X-ray spectroscopy and scanning electron and transmission electron microscopes to capture data on tension, bending, compression or nanoindentation of materials. These type of microscopic measurements are called in situ techniques.

Another technique studies how a metal alloy absorbs hydrogen and its effect on the metal. For example, Taşan played movies that show how plastic strain is accommodated to two phases in a high-entropy alloy.

“These techniques allow us to see how the failure process is taking place, and we use these techniques to understand the mechanism of these failure modes and potentially repair mechanisms. Finally, we use this understanding to design new alloys that utilize these mechanisms,” Taşan said. “You are trying to design a mechanism that can be used by the material over and over and over again to deal with the same type of crack that it is facing.”

Taşan’s investigations revealed three different types of crack closure mechanisms in steel: plasticity, phase transformation and crack-surface roughness. “If I want to activate all of these crack closure mechanisms, what I need to do is design a microstructure that is metastable, nano-laminate(d) and multi-phase at same time,” he said. He said the new steel alloy successfully combines all three characteristics.

Materials Research Laboratory Director Carl V. Thompson noted that how a material is made determines its structure and its properties. These properties include mechanical, electrical, optical, magnetic and many other properties. Materials science and engineering encompasses an entire cycle from designing methods for making materials through analyzing their structure and properties, to evaluating how they perform. “Ultimately most people go through this process to make materials that perform in either a new way or in a better way for systems like automobiles, your cell phone, or medical equipment,” Thompson said.

Engineering perovskite solar cells

Silvija Gradečak, Professor in Materials Science and Engineering, addressed the promise and the problems of perovskite solar cells. Hybrid organic-inorganic perovskites, such as methyl ammonium lead iodide, are a class of materials that are named after their crystal structure. “They are potentially lightweight, flexible and inexpensive as photovoltaic devices,” Gradečak said.

However, perovskite solar devices tend to be unstable in water, oxygen exposure, UV irradiation, and under voltage biasing. As many of these changes are dynamic and happen at nanoscale, understanding the structure of these materials can be complemented with information from electrical currents. “By using the electron beam, we can mimic the condition of the electron current within the device,” she said.

Gradečak uses a technique called cathodoluminescence to probe these perovskite materials. “Our cathodoluminescence setup is unique because it enables so-called hyperspectral imaging. It means that the full optical signal is detected in each point of the complementary structural image. As the beam interacts with the sample, we are detecting light, and we do this as the electron beam moves across the sample. That is specifically important for samples that are unstable as they are irradiated with the electron beam,” she says.

This technique revealed that perovskite material examined under an electron microscope while applying a voltage to the sample for 1 minute resulted in a dramatic current increase in the material. “That also corresponds to the I/V (current/voltage) measurements outside of the scanning electron microscope that we performed,” she said. When the voltage bias is removed, the sample relaxes back to its initial state.

“What we think is really happening is that by biasing, there are ions that are moving and they agglomerate at the edges of the sample or at the grain boundaries, and after you remove the bias, they will relax back,” Gradečak said.

Work in Gradečak’s group by Olivia Hentz (PhD ’18) combined photoluminescence data with Monte Carlo simulations to extract mobility of the defects that are moving. “More interesting, and how we can apply this method, is to understand how the material’s properties are influenced by synthesis. If you synthesize the material and you change, for example, the grain size, we can think about whether these ions that are moving will have different mobilities inside of the grain versus along the grain boundaries,” Gradečak said.

Hentz found that the mobility at the grain boundaries is 1,500 times faster than in the bulk. “The ions do move in the material, they move under the biasing conditions and that mobility is very different inside of the grain and along the grain boundaries,” Gradečak said. “By engineering the material and engineering the grain size, one can influence by how much the material will be influenced during the device operation. And this result correlates with the fact that single crystalline perovskite materials are significantly more stable than polycrystalline ones.”

Transformative new tools

In the Keynote address, BP Amoco Chemical Company Senior Research Chemist Dr. Matthew Kulzick detailed new X-ray technologies and sample chambers that are yielding insights into fighting metal corrosion, improving catalytic reactions and more. “The current evolution of tools is spectacular,” he said, noting the stunning images at 20-nanometer scale showing highly localized composition of materials.

MIT Nuclear Reactor Lab Director David E. Moncton discussed advances in X-ray tubes, noting that current versions of small scale X-ray tubes are about 100 times better than those of 100 years ago. X-ray source brilliance is increasing at two times Moore’s Law, which predicted the exponential growth of transistors in silicon chips, he noted.

Still Synchroton sources such as the Advanced Photon Source a national user facility at Argonne National Laboratory, offer beam brilliance that is 12 orders of magnitude higher than X-ray tubes. “Advanced X-ray capability is the most important missing probe of matter at nano centers and materials research labs that are not located at synchrotron facilities,” he said.

Compact X-ray free-electron laser devices hold the promise of bringing synchrotron-like examination capabilities to campus research labs, Moncton said. Moncton, who was the founding director of the Advanced Photon Source, is collaborating with Associate Professor William S. Graves at Arizona State, which is home to world’s first compact X-ray free-electron laser (CXFEL).

“The emittance is very similar to a synchrotron source,” Moncton said. “If you built a compact X-ray FEL on this compact source platform, it would outperform today’s synchrotron facilities by a number of orders of magnitude.”

X-ray phase contrast imaging has also advanced microscopy, Moncton said, displaying an image showing air bubbles in the lungs of a fruit fly. Pump-probe techniques enable studies of biological proteins performing bio-chemical processes in real time.

“Having a local synchrotron-like source would be revolutionary,” Moncton said.

Less damaging microscope

Professor of Electrical Engineering Karl Berggren described his efforts to develop a new type of electron microscope based on the quantum character of electrons to improve microscopy. One of the goals is to reduce radiation damage to biological samples from imaging them.

With support from the Gordon and Betty Moore Foundation, Berggren is collaborating on this research with Professor of Physics Mark Kasevich at Stanford University in California, Professor of Physics Peter Hommelhoff at the Friedrich Alexander University, Erlangen-Nürnberg, in Germany, and Professor of Physics Pieter Kruit at the Technical University of Delft in the Netherlands. “What we’d like to do is basically try to take advantage of the counter-intuitive quantum properties of electrons,” Berggren said.

In one approach, he employs a series of electron beam splitters and mirrors to improve the performance of scanning electron microscopes. “What we’re doing now is essentially making a test bed by which we can develop all the electron optics to try to put together a machine,” Berggren said. Along the way, his group has developed a microscope that lets you image the top and bottom of a sample at the same time.

“We know that electrons at high voltage will pass through many samples with interacting with just a small phase shift,” he said. “In fact, we want to work in that limit for imaging bio molecules.” The right combination of beam splitters could reduce electron-induced damage to the sample by 100 times, he said.

Nanowire self-assembly

Dr. Frances M. Ross, formerly of the Research Division at the IBM T. J. Watson Research Center and a new arrival at the Department of Materials Science and Engineering this academic year, described her observations of nanowire growth in an electron microscope. This vapor-liquid-solid process was first described in 1964, but the atomic-level details of how the nanowires grow could not be observed until recent improvements in electron microscopy technique.

Movie shows the growth of a silicon nanowire (lower region) from a catalytic droplet of gold silicon (AuSi) liquid (dark hemisphere above). Growth takes place by rapid addition of planes of silicon atoms at the catalyst/silicon interface. The nanowire diameter is 50 nanometers and growth took place at 500oC. Video courtesy of Frances M. Ross. Reproduced from Chou et al., “Nanowire growth kinetics in aberration corrected environmental transmission electron microscopy,” Chem. Commun., 2016, 52, 5686-5689, with permission from The Royal Society of Chemistry."

Showing a movie of a silicon nanowire growing from a gold-silicon catalyst droplet, Ross said, “To grow these silicon nanowires, we just put gold on silicon and heat it up. The gold and silicon automatically form droplets, in the same way that water forms droplets on a sheet of glass.” When additional silicon is then supplied, the droplets act as a catalyst and a silicon nanowire grows from each droplet. “Nanowire growth illustrates the fact that we can get a self-assembly process that is intrinsically very simple to form a structure that can be quite complex,” Ross explained. “You can see features like the atomic level structure of the nanowire and catalyst, the effect of temperature and gas environment, and even the dynamics of the growth interface and how the catalyst really works.” The silicon nanowire grows in little jumps despite a steady flow of source material, she noted, providing detailed information on the pathways by which the atoms assemble into the nanowire.

Adding nickel to this process resulted in a nickel disilicide particle embedded in the silicon nanowire – a quantum dot. “You almost expect to see unexpected things because the movies capture every point along the way as the material evolves,” Ross said. “In situ microscopy is really the only way to get these type of detailed relations between the structure, the properties and even the catalytic activity of individual nanoscale objects.”

“We’re in a very exciting time for electron microscopy, where advances in instrumentation are helping us understand materials growth at the atomic scale,” Ross said.

Uncovering crystal structure

James LeBeau, Visiting Professor of Materials Science and Engineering, explained that scanning transmission electron microscopy provides direct imaging of atomic structure using an extremely small (< 1x10-10 m) electron probe. LeBeau uses the scanning transmission electron microscope to develop and apply new ways to characterize atomic structure of materials to understand their properties. Further, he is applying machine learning to control the microscope, using an approach similar to that used to enable self-driving cars to recognize signs and lane lines.

Beyond imaging, “we can also acquire a full chemical spectrum at every single point in our dataset. This allows us to not only directly determine which atoms are in the material, but their bonding configuration as well,” LeBeau explained. He displayed an image showing lanthanum atoms sharing a sub-lattice with strontium and aluminum sharing a sub-lattice with tantalum. “These datasets become directly interpretable. You see the chemistry,” he said.

“We can even use this data to measure the atomic scale electric field,” LeBeau said, showing an image in which the color represents the electrostatic field vector and the intensity of the color represents its magnitude. LeBeau also was able to use these techniques to uncover the particular crystal structure of ferroelectric hafnium dioxide (HfO2). The atomic scale insights are critical as hafnium dioxide is compatible with silicon processing technology, which will pave the way for new memory applications. “By combining different types of data, we can explain the origin or ferroelectricity in these films and really rule out alternative explanations,” he said.

Twenty graduate students and postdocs gave two-minute previews during the Materials Day Symposium, which was immediately followed by a Poster Session. In all, 60 presented research posters in La Sala de Puerto. The winning presenters were graduate students Vera Schroeder, Rachel C. Kurchin, Gerald J. Wang and Philipp Simons, and Postdoctoral Associate Mikhail Y. Shalaginov.

back to newsletterDenis Paiste, Materials Research Laboratory
October 29, 2018

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