Microfluidic device generates passive hydraulic power, may be used to make small robots move.
|MIT engineers have designed a microfluidic device they call a “tree-on-a-chip,” which mimics the pumping mechanism of trees and other plants.|
Trees and other plants, from towering redwoods to diminutive daisies, are nature’s hydraulic pumps. They are constantly pulling water up from their roots to the topmost leaves, and pumping sugars produced by their leaves back down to the roots. This constant stream of nutrients is shuttled through a system of tissues called xylem and phloem, which are packed together in woody, parallel conduits.
Now engineers at MIT and their collaborators have designed a microfluidic device they call a “tree-on-a-chip,” which mimics the pumping mechanism of trees and plants. Like its natural counterparts, the chip operates passively, requiring no moving parts or external pumps. It is able to pump water and sugars through the chip at a steady flow rate for several days. The results are published this week in Nature Plants.
Anette “Peko" Hosoi, professor and associate department head for operations in MIT’s Department of Mechanical Engineering, says the chip’s passive pumping may be leveraged as a simple hydraulic actuator for small robots. Engineers have found it difficult and expensive to make tiny, movable parts and pumps to power complex movements in small robots. The team’s new pumping mechanism may enable robots whose motions are propelled by inexpensive, sugar-powered pumps.
Read more at the MIT News Office.
Jennifer Chu | MIT News Office
March 20, 2017
Novel laminated nanostructure gives steel bone-like resistance to fracturing under repeated stress.
|Researchers at MIT and in Japan and Germany, have developed a type of steel with three characteristics that help it resist microcracks that lead to fatigue failure –: a layered nanostructure, a mixture of microstructural phases with different degrees of hardness, and a metastable composition. They compared samples of metal with just one or two of these key attributes (top left, top right, and bottom left) and with all three (bottom right). The metal alloy with all three attributes outperformed all the others in crack resistance. Images, Courtesy of the researchers|
Metal fatigue can lead to abrupt and sometimes catastrophic failures in parts that undergo repeated loading, or stress. It’s a major cause of failure in structural components of everything from aircraft and spacecraft to bridges and powerplants. As a result, such structures are typically built with wide safety margins that add to costs.
Now, a team of researchers at MIT and in Japan and Germany has found a way to greatly reduce the effects of fatigue by incorporating a laminated nanostructure into the steel. The layered structuring gives the steel a kind of bone-like resilience, allowing it to deform without allowing the spread of microcracks that can lead to fatigue failure.
The findings are described in a paper in the journal Science by C. Cem Tasan, the Thomas B. King Career Development Professor of Metallurgy at MIT; Meimei Wang, a postdoc in his group; and six others at Kyushu University in Japan and the Max Planck Institute in Germany.
“Loads on structural components tend to be cyclic,” Tasan says.
Read more at the MIT News Office.
David L. Chandler | MIT News Office
March 9, 2017
Physics professor and former U.S. Energy Secretary will lead nuclear security nonprofit while continuing his work at MIT.
Nuclear physicist Ernest J. Moniz has been named chief executive officer and co-chairman of the board of the Nuclear Threat Initiative (NTI), a role he will assume in June.
Moniz, the former U.S. Secretary of Energy, has recently returned to MIT as a part-time professor of physics post-tenure and special advisor to the president. He will continue working in this capacity while taking on the new role.
A nonprofit, nonpartisan organization, NTI works to protect lives, the environment, and quality of life today and for future generations. Working with international leaders, scientists, educators, and the public, NTI works to prevent catastrophic attacks with weapons of mass destruction and disruption (WMDD) — nuclear, biological, radiological, chemical, and cyber.
Read more at the MIT News Office.
March 23, 2017
The Materials Processing Center and the Center for Materials Science and Engineering have selected 12 outstanding undergraduates to conduct graduate-level research on the MIT campus in Cambridge, Mass., from June 15, 2017 to August 5, 2017.
|Suna Njie, a 2016 Summer Scholar, soaks graphene in water to remove an etching solution. She worked in the Strano Lab at MIT under postdoc Pingwei Liu. Photo, Denis Paiste, Materials Processing Center|
This year’s Summer Scholars are:
• Alejandro Aponte, University of Puerto Rico, Mayaguez
• Stephanie Bauman, University of South Florida
• Lucia Brunel, Northwestern University
• Richard Canty, University of Virginia
• Amrita Duggal, California State University, Channel Islands
• Kaila Holloway, Howard University
• Saleem Iqbal, University of New Mexico
• Gaetana Michelet, University of Puerto Rico, Mayaguez
• Grace Noel, The Pennsylvania State University
• Alexandra Oliveira, University of Connecticut
• Kirill Shmilovich, University of Wisconsin - Milwaukee
• Luke Soule, New Mexico Institute of Mining and Technology
Interns select their own projects from faculty presentations given during the first few days of the program. MPC and the CMSE sponsor the eight-week National Science Foundation Research Experience for Undergraduates internships with support from NSF’s Materials Research Science and Engineering Centers program [grant DMR-14-19807].
A bio-inspired gel material developed at MIT could help engineers control movements of soft robots.
View the embedded image gallery online at:
A new material that naturally adapts to changing environments was inspired by the strength, stability, and mechanical performance of the jaw of a marine worm. The protein material, which was designed and modeled by researchers from the Laboratory for Atomistic and Molecular Mechanics (LAMM) in the Department of Civil and Environmental Engineering (CEE), and synthesized in collaboration with the Air Force Research Lab (AFRL) at Wright-Patterson Air Force Base, Ohio, expands and contracts based on changing pH levels and ion concentrations. It was developed by studying how the jaw of Nereis virens, a sand worm, forms and adapts in different environments.
The resulting pH- and ion-sensitive material is able to respond and react to its environment. Understanding this naturally-occurring process can be particularly helpful for active control of the motion or deformation of actuators for soft robotics and sensors without using external power supply or complex electronic controlling devices. It could also be used to build autonomous structures.
“The ability of dramatically altering the material properties, by changing its hierarchical structure starting at the chemical level, offers exciting new opportunities to tune the material, and to build upon the natural material design towards new engineering applications,” wrote Markus J. Buehler, the McAfee Professor of Engineering, head of CEE, and senior author of the paper.
The research, recently published in ACS Nano, shows that depending on the ions and pH levels in the environment, the protein material expands and contracts into different geometric patterns.
Read more at the MIT News Office.
Carolyn Schmitt | Department of Civil and Environmental Engineering
March 20, 2017
Graduate students, postdocs must apply by March 31, 2017, for two-week program featuring leaders in Quantum Computing science and technology.
|Ion qubit modules (small cubes on left) can be linked using photonic interconnects. A switch, depicted here as the large cube on right, would contain microelectromechanical mirrors to change connections between any arbitrary pair of modules. Illustration, Emily Edwards, Joint Quantum Institute and University of Maryland.|
The Quantum Science Summer School (QS3), a program jointly organized by MIT, Johns Hopkins University, Cornell University and Pennsylvania State University, kicks off this summer with its initial two-week session focused on “Fundamentals and Applications of Quantum Computing.”
The program will be held from June 5 to 16, 2017, on the Johns Hopkins Homewood campus in Baltimore, Md. Jointly supported by the National Science Foundation and the Department of Energy, QS3 is open to qualified graduate students and postdoctoral associates with a maximum of 40 participants. Accepted participants will be awarded round-trip travel within the U.S. and attendance expenses. The application deadline is March 31, 2017.
“A summer school is a great opportunity for students to get in-depth exposure to new concepts and also to have extended interactions with leaders in the field as well as their peers,” says MIT Assistant Professor of Physics Joseph G. Checkelsky, who is one of the program organizers. “It’s an opportunity to develop a solid foundation in both the theoretical and experimental understanding in a setting that bridges the gap between classroom teaching and a research seminar.”
Just as the understanding of quantum mechanics in the early 1900s unleashed a wave of new science and technology from the laser to the transistor, science now appears poised for a second quantum revolution with breakthroughs in computing, communications, energy and other fields. “A critical component of this development is the education of the next generation of scientists in the principles, methods, and goals of this rapidly expanding field. There is a challenge here given the breadth of disciplines brought together in this area – reaching across mathematics, chemistry, physics, materials science, and engineering. An educational program that helps to address this challenge is a step towards the work in computing, telecommunications, and new energy technologies that will shape the 21st century,” Checkelsky says. Checkelsky previously served as co-organizer for the Boulder Condensed Matter and Materials Physics Summer School.
QS3 presentations are geared towards building up participants’ basic knowledge towards the cutting edge. “We’ve tried to prepare this school with all the necessary pieces,” he says. “Some aspects will touch on a student’s particular expertise, but they will undoubtedly also have broader exposure and a chance to learn something about the other sub-disciplines that are related to quantum science and quantum computing. That can be an invigorating educational experience, particularly as part of a focused summer school.”
The lecture-based program will include talks by:
• Jason Alicea, professor of theoretical physics, Caltech.
• Alán Aspuru-Guzik, professor of chemistry and chemical biology, Harvard.
• Danna Freedman, assistant professor of chemistry, Northwestern.
• Steven Girvin, deputy provost for science and technology and Eugene Higgins professor of physics and applied physics, Yale.
• John M. Martinis, Quantum Artificial Intelligence team, Google, & professor of condensed matter experimental physics, University of California, Santa Barbara.
• Douglas T. McClure, research staff member, experimental quantum computing, IBM Thomas J. Watson Research Center.
• Christopher Monroe, distinguished university professor and Bice Seci-Zorn professor of physics, University of Maryland.
• Scott D. Pakin, scientist, Programming Models team, Los Alamos National Laboratory.
• David S. Weiss, associate head for research and professor of physics, Pennsylvania State University.
The NSF/DOE Quantum Science Summer School is dedicated to educating graduate students and postdocs in the fields of condensed matter physics, materials science, and quantum science and their applications to new technologies in academic and industrial contexts.
Program organizers are: Joe Checkelsky, assistant professor of physics, MIT; Natalia Drichko, associate research scientist, physics and astronomy, Johns Hopkins University; Lawrence C. (1944) and Sarah W. Biedenharn Career Development Assistant Professor Liang Fu, MIT; Kyle Shen, associate professor of physics, Cornell Universit y; and Jun Zhu, associate professor of physics, Pennsylvania State University. The site of future summer programs will rotate.
Study sheds light on interactions that change the way heat and electricity move through microchips.
|Atomic irregularities in crystals, known as dislocations, are common defects, and they affect how heat dissipates through a silicon microchip or how well current flows through a silicon solar panel. New MIT research offers insights into how these crystal dislocations affect electrical and heat transport through crystals, at a microscopic, quantum mechanical level. The MIT team has found a new mathematical approach using a new quasiparticle they formulated called a “dislon,” which is a quantized version of a dislocation.|
New research offers insights into how crystal dislocations — a common type of defect in materials — can affect electrical and heat transport through crystals, at a microscopic, quantum mechanical level.
Dislocations in crystals are places where the orderly three-dimensional structure of a crystal lattice — whose arrangement of atoms repeats with exactly the same spacing — is disrupted. The effect is as if a knife had sliced through the crystal and then the pieces were stuck back together, askew from their original positions. These defects have a strong effect on phonons, the modes of lattice vibration that play a role in the thermal and electrical properties of the crystals through which they travel. But a precise understanding of the mechanism of the dislocation-phonon interaction has been elusive and controversial, which has slowed progress toward using dislocations to tailor the thermal properties of materials.
A team at MIT has been able to learn important details about how those interactions work, which could inform future efforts to develop thermoelectric devices and other electronic systems. The findings are reported in the journal Nano Letters, in a paper co-authored by postdoc Mingda Li, Department of Mechanical Engineering head Professor Gang Chen, the late Institute Professor Emerita Mildred Dresselhaus, and five others.
Dislocations — which Li describes as “atomic irregularities in a regular crystal” — are very common defects in crystals, and they affect, for example, how heat dissipates through a silicon microchip or how well current flows through a silicon solar panel.
Read more at the MIT News Office.
David L. Chandler | MIT News Office
March 14, 2017
Researchers have discovered a new way to tune electronic energy levels in some 2-D materials.
|Researchers at MIT have discovered a new way of using laser light to tune electronic energy levels in two-dimensional films of crystal. The discovery could ultimately pave the way for the development of so-called “valleytronic” devices, which harness the way electrons gather around two equal energy states, known as valleys. Photo, Jose-Luis Olivares, MIT.|
Faster, more efficient data storage and computer logic systems could be on the horizon thanks to a new way of tuning electronic energy levels in two-dimensional films of crystal, discovered by researchers at MIT.
The discovery could ultimately pave the way for the development of so-called “valleytronic” devices, which harness the way electrons gather around two equal energy states, known as valleys.
Engineers have for some time warned that we are reaching the limits of how small we can build conventional electronic transistors, which are based on electrons’ electrical charge.
As a result, researchers have been investigating the utility of a property of electrons known as spin, to store and manipulate data; such technologies are known as spintronics.
But as well as their charge and spin, electrons in materials also have another “degree of freedom,” known as the valley index. This is so-called because plotting the energy of electrons relative to their momentum results in a graph consisting of a curve with two valleys, which are populated by electrons as they move through a material.
Harnessing this degree of freedom could allow information to be stored and processed in some materials by selectively populating the two valleys with electrons.
However, developing such valleytronic devices requires a system to selectively control the electrons within the two valleys, which has so far proven very difficult to achieve.
In a paper published March 9 in the journal Science, researchers led by Nuh Gedik, an associate professor of physics at MIT, describe a new way of using laser light to control the electrons in both valleys independently, within atomically thin crystals of tungsten disulfide.
Read more at the MIT News Office.
Helen Knight | MIT News correspondent
March 9, 2017
Researchers discover that chaos makes carbon materials lighter and stronger.
In the quest for more efficient vehicles, engineers are using harder and lower density carbon materials, such as carbon fibers, which can be manufactured sustainably by "baking" naturally occurring soft hydrocarbons in the absence of oxygen. However the optimal "baking" temperature for these hardened, charcoal-like carbon materials remained a mystery since the 1950s when British scientist Rosalind Franklin, who is perhaps better known for providing critical evidence of DNA’s double helix structure, discovered how the carbon atoms in sugar, coal and similar hydrocarbons, react to temperatures approaching 3,000 degrees Celsius (5,432 F) in oxygen-free processing. Confusion over whether disorder makes these graphite-like materials stronger, or weaker, prevented identifying the ideal "baking" temperature for more than 40 years.
Fewer, more chaotically arranged carbon atoms produce higher strength materials, MIT researchers report in the journal Carbon. They find a tangible link between the random ordering of carbon atoms within a phenol-formaldehyde resin, which was “baked” at high temperatures, and the strength and density of the resulting graphite-like carbon material. Phenol-formaldehyde resin is a hydrocarbon commonly known as “SU-8” in the electronics industry. Additionally, by comparing the performance of the “baked” carbon material, the MIT researchers identified a “sweet spot” manufacturing temperature: 1,000 degrees Celsius (1,832 F).
“These materials we’re working with, which are commonly found in SU-8 and other hydrocarbons that can be hardened using ultraviolet [UV] light, are really promising for making strong and light lattices of beams and struts on the nanoscale, which only recently became possible due to advances in 3D printing,” says MIT postdoc Itai Stein [SM ’13, PhD ’16]. “But up to now, nobody really knew what happens when you’re changing the manufacturing temperature, that is, how the structure affects the properties. There was a lot of work on structure and a lot of work on properties, but there was no connection between the two. ... We hope that our study will help to shed some light on the governing physical mechanisms that are at play.”
Stein, who is the lead author of the paper published in Carbon, led a team under Professor of Aeronautics and Astronautics Brian L. Wardle, consisting of junior Chlöe V. Sackier, alums Mackenzie E. Devoe [SB ’15] and Hanna M. Vincent [SB, ’14], and undergraduate Summer Scholars Alexander J. Constable  and Naomi Morales-Medina .
“Our investigations into this carbon material as a matrix for nanocomposites kept leading to more questions making this topic increasingly interesting in and of itself. Through a series of contributions, notably from MIT undergraduate researchers and Summer Scholars, a sustained investigation of several years resulted, allowing some paradoxical results in the extant literature to be resolved,” says Prof. Wardle.
By “baking” the resin at high temperature in inert gas, a process commonly known as pyrolysis, the researchers formed a type of disordered graphite-like carbon material that is often called glassy carbon. Stein and Wardle showed that when it is processed at temperatures higher than 1,000 degrees Celsius, the material becomes more ordered but weaker. They estimated the strength of their glassy carbon by applying a local force and measuring their material's ability to resist deformation. This type of measurement, which is known to engineers as the Vickers hardness test, is a highly versatile technique that can be used to study a wide variety of materials, such as metals, glasses, and plastics, and enabled the researchers to compare their findings to many well-known engineering materials that include diamond, carbon fiber composites, and metal carbides.
Some disorder is good
The carbon atoms within the MIT researchers' material were more chaotically organized than is typical for graphite, and this was because phenol-formaldehyde with which they started is a complicated mix of carbon-rich compounds. “Because the hydrocarbon was disordered to begin with, a lot of the disorder remains in your crystallites, at least at this temperature,” Stein explains. In fact, the presence of more complex carbon compounds in the material strengthens it by leading to three-dimensional connections that are hard to break. “Basically you get pinned at the crystallite interface, and that leads to enhanced performance,” he says.
These high-temperature baked materials have only one carbon atom in their structure for every three in a diamond structure. “When you’re using these materials to make nanolattices, you can make the overall lattice even less dense. Future studies should be able to show how to make lighter and cheaper materials,” Stein suggests. Hydrocarbons similar to the phenol-formaldehyde studied here can also be sourced in an environmentally friendly way, he says.
“Up until now there wasn’t really consensus about whether having a low density was good or bad, and we’re showing in this work, that having a low density is actually good,” Stein says. That’s because low density in these crystallites means more molecular connections in three dimensions, which helps the material resist shearing, or sliding apart. Because of its low density, this material compares favorably to diamond and boron nitrides for aerospace uses. “Essentially you can use a lot more of this material and still end up saving weight overall,” Stein says.
“This study represents sound materials science – connecting all three facets of synthesis, structure, and property – toward elucidating poorly understood scaling laws for mechanical performance of pyrolytic carbon,” says Dr. Eric Meshot, a staff scientist at Lawrence Livermore National Laboratory, who was not involved in this research. “It is remarkable that by employing routinely available characterization tools, the researchers pieced together both the molecular and nanoscale structural pictures and deciphered this counterintuitive result that more graphitization does not necessarily equal a harder material. It is an intriguing concept in and of itself that a little structural disorder can enhance the hardness.”
“Their structural characterization proves how and why they achieve high hardness at relatively low synthesis temperatures,” Meshot adds. “This could be impactful for industries seeking to scale up production of these types of materials since heating is a seriously costly step.” The study also points to new directions for making low-density composite structures with truly transformative properties, he suggests. “For example, by incorporating the starting SU-8 resin in, on, or around other structures (such as nanotubes as the authors suggest), can we synthesize materials that are even harder or more resistant to sheer? Or composites that possibly embed additional functionality, such as sensing?” Meshot asks.
The new research has particular relevance now because a group of German researchers showed last year in a Nature Materials paper how these materials can form highly structured nanolattices that are strong, lightweight and are outperformed only by diamond. Those researchers processed their material at 900 degrees Celsius, Stein notes. “You can do a lot more optimization, knowing what the scaling is of the mechanical properties with the structure, then you can go ahead and tune the structure accordingly, and that’s where we believe there is broad implication for our work in this study,” he says.
Summer Scholars role
Constable [Penn State, ’16] and Morales-Medina [University of Puerto Rico-Rio Piedras, ’15] participated in Wardle’s lab through the annual Summer Scholars program of the Materials Processing Center and the Center for Materials Science and Engineering at MIT, which is a National Science Foundation Research Experience for Undergraduates program [grants DMR-08-19762 and DMR-1419807]. “They were only here for a very short amount of time, and they got a lot of data collected,” Stein says. Morales-Medina, who is currently a PhD student at the Medical Physics Program at Duke University, developed techniques for the in situ X-Ray Diffraction used to evaluate how this pyrolytic carbon evolves as a function of temperature, and Constable, who is currently an M.Sc. Candidate in Engineering Mechanics at The University of Texas at Austin, collected data that was published in the current paper. They also quantified the crystal sizes and surface chemistries using shared experimental facilities at the Center for Materials Science and Engineering.
This work was partly supported by MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium members Airbus Group, Boeing, Embraer, Lockheed Martin, Saab AB, ANSYS, Hexcel, and TohoTenax. Stein was supported in part by a National Defense Science & Engineering Graduate Fellowship.
– Denis Paiste, Materials Processing Center
Updated March 17, 2017