MIT News: Energy Efficient And Precision Controlled Quantum Dots Developed

MIT researchers have developed a new production method in creating quantum dots that can control its size and shape, and also vastly improves the quantum dot's emission efficiency. This allows the development of energy efficient and precise devices such as computer screens and biomedical kits and applications.

In simple terms, quantum dots are nano-scale semiconductors that converts light into energy. These are parts of matter whose excitons (photons absorbed by a semiconductor) are bound in all three spatial dimensions. They are so small that quantum dots can be applied to most substrates or surfaces by spraying it on to form a layer of nano-film semiconductors.

Quantum dots are just a few atoms thick making it viable for use in nano-sized or micro-sized devices. Currently, some transistors, LEDs (Light emitting diodes), solar panels, and diode lasers utilize this technology. Some are even looking at quantum dots for use in quantum computers.

MIT News: MIT’s Institute for Medical Engineering and Science - A Source for Big Data Through bigdata@CSAIL

With the recent launch of MIT’s Institute for Medical Engineering and Science, MIT News examines research with the potential to reshape medicine and health care through new scientific knowledge, novel treatments and products, better management of medical data, and improvements in health-care delivery.

At the end of 2012, the National Public Radio show Fresh Air featured a segment in which its linguistics commentator argued that “big data” should be the word of the year. The term refers not only to the deluge of data produced by the proliferation of Internet-connected, sensor-studded portable devices but also to innovative techniques for analyzing that data; and big data has received a good deal of credit for Barack Obama’s victory in the last presidential election.

MIT News: New Process in Deforming Cells for Efficient Delivery of Large Molecules

As cells squeeze through a narrow channel, tiny holes open in their membranes, allowing large molecules such as RNA to pass through.
Image: Armon Sharei and Emily Jackson

Living cells are surrounded by a membrane that tightly regulates what gets in and out of the cell. This barrier is necessary for cells to control their internal environment, but it makes it more difficult for scientists to deliver large molecules such as nanoparticles for imaging, or proteins that can reprogram them into pluripotent stem cells.

Researchers from MIT have now found a safe and efficient way to get large molecules through the cell membrane, by squeezing the cells through a narrow constriction that opens up tiny, temporary holes in the membrane. Any large molecules floating outside the cell — such as RNA, proteins or nanoparticles — can slide through the membrane during this disruption.

Using this technique, the researchers were able to deliver reprogramming proteins and generate induced pluripotent stem cells with a success rate 10 to 100 times better than any existing method. They also used it to deliver nanoparticles, including carbon nanotubes and quantum dots, which can be used to image cells and monitor what’s happening inside them.

MIT News: Polymer Film Uses Water Vapor to Harvest Energy and Generate Electricity For Nanodevices

A polymer is a combination of chemical compounds that is made up of repeating structural units (as in a molecular structure). The structure of the polymer dictates it properties.

Polymers are usually associated with plastics. The material used for credit cards is a polymer, as well as PVC plastics and PET water bottles. But polymers can be in any form. Hairspray and mousse is a polymer. Fabrics like spandex are also polymers. While these are synthetic, there are also natural polymers like rubber and amber.

Since these are created at the molecular level, nanotechnology devices rely on polymers for structural, chemical, or containment purposes.

Recent developments that included polymers are microchips created by self assembling polymer; flicker free, bendable, and shatterproof lighting (FIPEL - Field-Induced Polymer Electroluminescent technology); and Organic Light Emitting Diodes (OLED).

Electricity Generating Polymer Film

MIT engineers have created a new polymer film that can generate electricity by drawing on a ubiquitous source: water vapor.

The new material changes its shape after absorbing tiny amounts of evaporated water, allowing it to repeatedly curl up and down. Harnessing this continuous motion could drive robotic limbs or generate enough electricity to power micro- and nanoelectronic devices, such as environmental sensors.

MIT News: Manipulating Heat Using Lenses and Mirrors

Thermal lattices, shown here, are one possible application of the newly developed thermocrystals. In these structures, where precisely spaced air gaps (dark circles) control the flow of heat, thermal energy can be "pinned" in place by defects introduced into the structure (colored areas).
Illustration courtesy of Martin MaldovanCredit: MIT

Nanostructured semiconductor alloy crystals were engineered to manipulate heat, either through reflecting or focusing it.

Nanotechnology is the science behind the manipulation of atomic and molecular objects. These materials measure from 1 to 100 nanometers (nm). One nanometer is equal to one billionth, or 10⁻⁹ meters.

Nanostructures are one of the products from this technology. Nanostructures are engineered as a component for a bigger device. Nanostructures give support, assist in the process, or brings out a particular property from the created device.

There are three dimensions to a nanostructure:

• Nanotextured surfaces have one dimension on the nanoscale - only the thickness of the surface of an object is between 0.1 and 100 nm (a dot).
• Nanotubes have two dimensions on the nanoscale - the diameter of the tube is between 0.1 and 100 nm; its length could be much greater.
• Spherical nanoparticles have three dimensions on the nanoscale - the particle is between 0.1 and 100 nm in each spatial dimension (Length, Width, Height).

MIT News: Efficient and Fast Algorithm For Information Dissemination of Decentralized Networks Developed

Ad hoc networks — communication networks set up on the fly by mobile sensors — pose problems that ordinary office networks don’t. Ad hoc networks are usually decentralized, meaning that no one node knows what the network as a whole looks like.

One of the questions raised by decentralized networks is how to relay messages so that they will reliably reach all the nodes, even when the network’s shape is unknown. At the ACM-SIAM Symposium on Discrete Algorithms this month, Bernhard Haeupler, a graduate student in MIT’s Department of Electrical Engineering and Computer Science, won one of two best-student-paper prizes for a new algorithm that answers that question.

Haeupler’s algorithm is faster than previous algorithms. But its real interest, he believes, is that it’s deterministic, meaning that it will provably relay messages to every node in a network. Previous algorithms, he explains, were probabilistic: No matter how long they were allowed to run, there would always be some minuscule chance that a message didn’t reach some nodes.

“In the distributed community, solving problems without randomization is often a completely different problem, and deterministic algorithms are often drastically slower,” Haeupler explains. “I don’t think that anyone really believed that you can do anything deterministically in this setting.”

MIT News: Increasing Heat Coefficients on Industrial Plant Condensers Through Nanotechnology

Students at the Device Research Lab (DRL) in MIT’s mechanical engineering department have designed and tested a coated surface of an industrial plant condenser with nanostructured patterns that greatly increase the heat-transfer coefficient.

The heat-transfer coefficient is important when it comes to condensers because it is a measure of how fast heat can be transferred away from it. Basically, it is the opposite of insulation where insulation is a measure of how long heat can be maintained.

The purpose of a condenser in an industrial plant, like a thermal power plant for example, is to condense water vapor back into steam for maximum efficiency and reuse the now transformed liquid water in the steam generator or boiler as boiler feed water. A condenser with a high heat-transfer coefficient would then be able to condense water vapor faster and more efficiently.

Nanostructures and its uses

Nanotechnology, specifically nanostructures, have been proven successful in creating materials or devices that perform in a particular way, usually increasing its efficiency in the process. Nanostructures are objects created at the nanoscale or atmolecular level. These are very tiny structures and creating a nanostructure involves manipulating an object's composition at a molecular level. It may involve moving molecules or atoms around, or creating patterns that will allow it to behave in a particular way.

These structures are made to either act as a container in a delivery system (like gas atom/molecule in a very tiny capsule), interact with other objects to achieve a predetermined outcome either structurally or chemically or to act as a base for a more complex structure.

In relation to the condenser created by MIT, the surface was coated with nanostructured patterns to influence the way water droplets behave on it (see embedded video below).

MIT News: Researchers develop cost-effective way to spin nanoscale fibers

Image: A tiny array of silicon tips sandwiched between electrodes spins out "nanofibers" of plastic that could be useful for a host of applications.
Photo: Dominick Reuter

Nanofibers — strands of material only a couple hundred nanometers in diameter — have a huge range of possible applications: scaffolds for bioengineered organs, ultrafine air and water filters, and lightweight Kevlar body armor, to name just a few. But so far, the expense of producing them has consigned them to a few high-end, niche applications.

Luis Velásquez-García, a principal research scientist at MIT’s Microsystems Technology Laboratories, and his group hope to change that. At the International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications in December, Velásquez-García, his student Philip Ponce de Leon, and Frances Hill, a postdoc in his group, will describe a new system for spinning nanofibers that should offer significant productivity increases while drastically reducing power consumption.

Shear Thinning Hydrogels Developed For Cancer Treatment

Graphic: Christine Daniloff

Gels that can be injected into the body, carrying drugs or cells that regenerate damaged tissue, hold promise for treating many types of disease, including cancer. However, these injectable gels don’t always maintain their solid structure once inside the body.

MIT chemical engineers have now designed an injectable gel that responds to the body’s high temperature by forming a reinforcing network that makes the gel much more durable, allowing it to function over a longer period of time.

The research team, led by Bradley Olsen, an assistant professor of chemical engineering, described the new gels in a recent issue of the journal Advanced Functional Materials. Lead author of the paper is Matthew Glassman, a graduate student in Olsen’s lab. Jacqueline Chan, a former visiting student at MIT, is also an author.

MIT News: Speeding Up GPS Algorithms Through Data Compression, Line Simplification, and Signal Clustering

MIT Researchers have devised an algorithm that is fast and efficient by compressing the data and processing them into smaller data coresets. This approach which they applied to a GPS program can also be utilized by other algorithms.

Computers process data based on a series of sequential procedures in performing its calculations. This is called an algorithm. Algorithms help computers decide how to treat data without consulting the user.

But how does an algorithm work? Here is a sample algorithm to see if the user is old enough to register in a website. First the program asks the user to input his birthday. The computer checks the present age based on the birthday. If the result is below the allowed age, then the computer informs the user he is too young to register for the sit.

MIT News: Researchers Improve Electron Microscopy Using Engineered Protein Labels

A fluorescent microscope is an optical microscope that is used to observe specimens that undergo a fluorescence or phosphorescence stage. The specimen has small molecules called fluorophores attached to it. These fluorophores emit light when irradiated with a specific wavelength of light. This causes the specimen to be illuminated from within the specimen itself, generating a much more detailed image.

The molecule used in making the specimen fluorescent is the green fluorescent protein (GFP). It gives off a bright green fluorescence when exposed to light in the blue to ultraviolet range. GFP is generally safe to use when illuminating live cells.

This imaging technique has revolutionized molecular biology. But since fluorescent microscopes are optical in nature, this technique cannot be used with electron microscopes. Optical microscopes uses light beams to image a specimen, electron microscopes use beams of electrons to produce a magnified image.

MIT News: Bending Light To Cloak Objects Lead To Better Electron Transfer For Thermoelectric Devices

A new approach that allows objects to become “invisible” has now been applied to an entirely different area: letting particles “hide” from passing electrons, which could lead to more efficient thermoelectric devices and new kinds of electronics.

Diagram shows the 'probability flux' of electrons, a representation of the paths of electrons as they pass through an 'invisible' nanoparticle. While the paths are bent as they enter the particle, they are subsequently bent back so that they re-emerge from the other side on the same trajectory they started with — just as if the particle wasn't there.
Image courtesy Bolin Liao et al.

The concept — developed by MIT graduate student Bolin Liao, former postdoc Mona Zebarjadi (now an assistant professor at Rutgers University), research scientist Keivan Esfarjani, and mechanical engineering professor Gang Chen — is described in a paper in the journal Physical Review Letters.

MIT News: Asteroid Vesta Once Had Dynamo That Generated Magnetic Field Like The Earth

On September 27, 2007, NASA launched its Dawn spacecraft. Its mission is to orbit the asteroid Vesta and then head over to another asteroid, Ceres.

Both Vesta and Ceres are situated in the asteroid field between Mars and Jupiter. Dawn's goal is to investigate in detail the two asteroids which are the largest protoplanets still intact. Protoplanets are small celestial bodies that show the beginning formation of a planet. These are differentiated objects which means, that these protoplanets underwent a process where their interior got hot enough to melt separating elements within into layers.

Vesta is a dry, differentiated object that has a rocky surface which resemble some features found on the Earth.

Last year, data from the Dawn mission revealed that Vesta may be the smallest terrestrial planet in the solar system. Meteorites found on Earth believed to have come from Vesta has shown extensive igneous processing not much different from the magma rocks found on Earth. This process makes them closely resemble terrestrial igneous rocks.

MIT News: Mystery Behind Human Language May Be Explained Through Information Theory

MIT researchers are now looking at the nuances of how a sentence is constructed. Across cultures, basic sentence structures fall into two basic groups.

One group, a sentence is formed with a subject-verb-object (SVO) structure. An example would be "The man reads the sign". The second way to form a sentence which is like the Japanese would be the subject-object-verb (SOV) structure. The same sentence example would come out like this: "The man the sign reads".

Researchers are now looking at information theory for finding the reason why 85% of culture use these two language structures.

What is Information Theory?

Information theory is the science of quantifying information. It studies how communication signals can be reduced down to its most fundamental basic limit of information.

Information theory is not to be confused with information science. Information science is primarily concerned with the analysis, collection, classification, manipulation, storage, retrieval and dissemination of information.

Information theory is used in processes such as compressing, storage, and transmission of data. It tries to find the minimum amount of bits needed to store or communicate a word or symbol in a message without compromising the message itself.

MIT News: Understanding Tumor Metastasis, Cancer, And Cellular Adhesion

A microscopic image of cancer cells adhering to a spot coated with molecules found in the extracellular matrix.
Image: Nathan Reticker-Flynn

Cancer researchers at MIT are focusing their attention on how tumor metastasis occurs. Metastasis is the spread of the tumor to other parts of the body and is the primary reason for ninety percent of all cancer deaths. Their findings are published in the October issue of Nature Communications.

When a tumor metastasize, cancerous cells detach from the primary tumor and spread to other organs through the blood stream. The team of researchers headed by Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science, are studying how the anchoring process works within the tumor.

“As cancer cells become more metastatic, there can be a loss of adhesion to normal tissue structures. Then, as they become more aggressive, they gain the ability to stick to, and grow on, molecules that are not normally found in healthy tissues but are found in sites of tumor metastases,” says Bhatia, who is also a member of the David H. Koch Institute for Integrative Cancer Research at MIT. “If we can prevent them from growing at these new sites, we may be able to interfere with metastatic disease.”

Cells bind itself to a tissue surface or extracellular matrix because of cell adhesion. The extracellular matrix is a structural support system that holds cells in place and also regulates its behavior. On the surface of the matrix are cell adhesion molecules such as the protein Integrin that anchor the cells in place. Integrins can communicate with the cellular matrix both ways, meaning it can send signals from the matrix environment to the matrix and vice-versa.

The scientists tested eight hundred different protein pairs to find out how the cells will bind to them. They noticed that one pair of extracellular matrix molecules that metastatic tumors stuck to especially well was fibronectin and galectin-3, both made of proteins that contain or bind to sugars. Integrin works especially well with fibronectin.

MIT News - Studying Screw Dislocation on Iron Crystal Lattice To Understand Stress, Impacts and Fractures In Materials

A dislocation in a crystal lattice, a disconnected region in its structure (represented by the array of atoms shown in blue) can separate from the rest of the lattice at a rate determined by the potential energy of the system, represented by the wavy surface. To the left, the higher potential energy (shown in red) prevents the defect from moving in that direction, but to the lower right (shown in blue) the defect can glide toward a lower-energy state, if it first overcomes the higher-energy hump. Once over that hump, it can move rapidly and continuously — a condition called flow stress.
Image courtesy of Yue Fan and Bilge Yildiz

Diving into a pool from a few feet up allows you to enter the water smoothly and painlessly, but jumping from a bridge can lead to a fatal impact. The water is the same in each case, so why is the effect of hitting its surface so different?

This seemingly basic question is at the heart of complex research by a team in MIT’s Department of Nuclear Science and Engineering (NSE) that studied how materials react to stresses, including impacts. The findings could ultimately help explain phenomena as varied as the breakdown of concrete under sudden stress and the effects of corrosion on various metal surfaces.

Using a combination of computer modeling and experimental tests, the researchers studied one specific type of stress — in a defect called a screw dislocation — in one kind of material, an iron crystal lattice. But the underlying explanation, the researchers say, may have broad implications for many kinds of stresses in many different materials.

The research, carried out by doctoral student Yue Fan, associate professor Bilge Yildiz, and professor emeritus Sidney Yip, is being published this week in the journal Physical Review Letters.

Essentially, the team analyzed how the strength of a material can increase quite abruptly as the rate of strain applied to the material increases. This transition in the rate at which a material cracks or bends, called a flow-stress upturn, has been observed experimentally for many years, but its underlying mechanism has never been fully explained, the researchers say.

“The formulation is not specific to this particular defect,” Yildiz explains. Rather, she and her colleagues have figured out what they believe is a set of general principles. “We have proven that it works in this system,” she says.

“There are implications that go beyond dislocations, beyond even crystals,” Yip adds. But before extending the work — something the team is working on now — the researchers had to prove the principle by applying it to a specific case, in this case the screw dislocation in iron. While other researchers have analyzed behaviors associated with particular kinds of defects in specific materials, with these new general principles, “all of a sudden we have an explanation for their data that does not require such specific assumptions,” Yip says.

MIT News: Astrocyte Brain Cells Plays Key Role In Processing Sensory Information

How attention helps you remember

A new study from MIT neuroscientists sheds light on a neural circuit that makes us likelier to remember what we’re seeing when our brains are in a more attentive state.

The team of neuroscientists found that this circuit depends on a type of brain cell long thought to play a supporting role, at most, in neural processing. When the brain is attentive, those cells, called astrocytes, relay messages alerting neurons of the visual cortex that they should respond strongly to whatever visual information they are receiving.

The findings, published this week in the online edition of the Proceedings of the National Academy of Sciences, are the latest in a growing body of evidence suggesting that astrocytes are critically important for processing sensory information, says Mriganka Sur, the Paul E. and Lilah Newton Professor of Neuroscience at MIT and senior author of the paper.

MIT News: Tissue Implants Made Of Engineered Cells Depends On Scaffold Grown

Principle of tissue engineering

Success of engineered tissue depends on where it’s grown

Tissue implants made of cells grown on a sponge-like scaffold have been shown in clinical trials to help heal arteries scarred by atherosclerosis and other vascular diseases. However, it has been unclear why some implants work better than others.

MIT researchers led by Elazer Edelman, the Thomas D. and Virginia W. Cabot Professor of Health Sciences and Technology, have now shown that implanted cells’ therapeutic properties depend on their shape, which is determined by the type of scaffold on which they are grown. The work could allow scientists to develop even more effective implants and also target many other diseases, including cancer.

“The goal is to design a material that can engineer the cells to release whatever we think is most appropriate to fight a specific disease. Then we can implant the cells and use them as an incubator,” says Laura Indolfi, a postdoc in Edelman’s lab and lead author of a paper on the research recently published online in the journal Biomaterials.

Aaron Baker, a former postdoc in Edelman’s lab and now an assistant professor at the University of Texas at Austin, is also an author of the paper.

Shape matters

For the past 20 years, Edelman has been working on using endothelial cells grown on scaffolds made of collagen as implantable devices to treat blood vessel damage. Endothelial cells line the blood vessels and regulate important process such as tissue repair and inflammation by releasing molecules such as chemokines, small proteins that carry messages between cells.

Several of the devices have been tested in clinical trials to treat blood vessel damage; in the new Biomaterials study, Edelman and Indolfi set out to determine what makes one such tissue scaffold more effective than another. In particular, they were interested in comparing endothelial cells grown on flat surfaces and those grown on more porous, three-dimensional scaffolds. The cells grown on 3-D structures tended to be more effective at repairing damage and suppressing inflammation.

The researchers found that cells grown on a flat surface take on a round shape in which the cells’ structural components form a ring around the perimeter of the cell. However, when cells are grown on a scaffold with surfaces of contact whose dimensions are similar in size to the cells, they mold to the curved surfaces, assuming a more elongated shape. In those cells, the structural elements — made of bundles of the protein actin — run parallel to each other.

MIT News: Algorithm Developed For Determining Trajectory For Robot Planes Without GPS

A small, autonomous helicopter, programmed by MIT students under the direction of Professor Nick Roy, passes through a simulated window as part of a competition held over the summer. (2009 Pic)
Credit: Nicholas Roy

Autonomous robotic plane flies indoors

For decades, academic and industry researchers have been working on control algorithms for autonomous helicopters — robotic helicopters that pilot themselves, rather than requiring remote human guidance. Dozens of research teams have competed in a series of autonomous-helicopter challenges posed by the Association for Unmanned Vehicle Systems International (AUVSI); progress has been so rapid that the last two challenges have involved indoor navigation without the use of GPS.

But MIT’s Robust Robotics Group — which fielded the team that won the last AUVSI contest — has set itself an even tougher challenge: developing autonomous-control algorithms for the indoor flight of GPS-denied airplanes. At the 2011 International Conference on Robotics and Automation (ICRA), a team of researchers from the group described an algorithm for calculating a plane’s trajectory; in 2012, at the same conference, they presented an algorithm for determining its “state” — its location, physical orientation, velocity and acceleration. Now, the MIT researchers have completed a series of flight tests in which an autonomous robotic plane running their state-estimation algorithm successfully threaded its way among pillars in the parking garage under MIT’s Stata Center.

“The reason that we switched from the helicopter to the fixed-wing vehicle is that the fixed-wing vehicle is a more complicated and interesting problem, but also that it has a much longer flight time,” says Nick Roy, an associate professor of aeronautics and astronautics and head of the Robust Robotics Group. “The helicopter is working very hard just to keep itself in the air, and we wanted to be able to fly longer distances for longer periods of time.”

With the plane, the problem is more complicated because “it’s going much faster, and it can’t do arbitrary motions,” Roy says. “They can’t go sideways, they can’t hover, they have a stall speed.”

Found in translation

To buy a little extra time for their algorithms to execute, and to ensure maneuverability in close quarters, the MIT researchers built their own plane from scratch. Adam Bry, a graduate student in the Department of Aeronautics and Astronautics and lead author on both ICRA papers, consulted with AeroAstro professor Mark Drela about the plane’s design. “He’s a guy who can design you a complete airplane in 10 minutes,” Bry says. “He probably doesn’t remember that he did it.” The plane that resulted has unusually short and broad wings, which allow it to fly at relatively low speeds and make tight turns but still afford it the cargo capacity to carry the electronics that run the researchers’ algorithms.

MIT News: New Digital Based Woodworking Tool Can Cut Accurate Shapes

From left to right: Ilan E. Moyer, Alec Rivers, Frédo Durand.
Photo: Frédo Durand

New router enhances the precision of woodworking

Anyone who has tried to build a piece of furniture from scratch knows the frustration of painstakingly cutting pieces of wood, only to discover that they won’t fit together because the cutting was not quite accurate enough.

That’s exactly what happened to Alec Rivers, a PhD student in the Computer Science and Artificial Intelligence Laboratory (CSAIL) at MIT, when he attempted to build a simple picture frame using woodworking equipment he had inherited from his grandfather. Despite measuring and aligning his tools as best he could by hand, Rivers found that he could not produce shapes with enough precision to make them all fit together. “I was getting incredibly frustrated, because just as with any home project I would cut things out and they would look about right, but none of the pieces would line up,” Rivers says.

But rather than simply throwing the pieces of wood into the trash and settling for a store-bought picture frame, Rivers decided there had to be a better way. So he and colleagues Fredo Durand, an associate professor at CSAIL, and Ilan Moyer, a graduate student in the Department of Mechanical Engineering, began developing a new kind of woodworking router — a drill-like cutting tool — that could automatically cut out accurate shapes from a piece of material by following a digital design. The result is a handheld device that can adjust its position to precisely follow a digital plan when the user moves the router roughly around the shape to be cut.

The team will present its device this week at the Siggraph conference in Los Angeles.

“You load the system up with a digital plan that you would like it to follow, and then you are only responsible for getting it to within a quarter-inch or so of that plan,” Rivers says. “The device then adjusts the position of the cutting bit within the tool to keep it to the plan.”

For the device to follow the design, it must know exactly where it is on the sheet of material at all times. So before beginning to cut, the user first moves the device over the raw material, while an on-board camera films the surface and then stitches together all the video frames it sees into a single cohesive 2-D map of the piece. To ensure that the system can locate itself even when the material has no distinctive pattern or markings, the user simply places stickers containing a black and white contrast pattern on the sheet to be cut.