Tag Archives: MIT

Solar-powered sensors to power the Internet of Things?

As a June 23, 2015 news item on Nanowerk notes, the ‘nternet of things’, will need lots and lots of power,

The latest buzz in the information technology industry regards “the Internet of things” — the idea that vehicles, appliances, civil-engineering structures, manufacturing equipment, and even livestock would have their own embedded sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks.

Realizing that vision, however, will require extremely low-power sensors that can run for months without battery changes — or, even better, that can extract energy from the environment to recharge.

Last week, at the Symposia on VLSI Technology and Circuits, MIT [Massachusetts Institute of Technology] researchers presented a new power converter chip that can harvest more than 80 percent of the energy trickling into it, even at the extremely low power levels characteristic of tiny solar cells. [emphasis mine] Previous experimental ultralow-power converters had efficiencies of only 40 or 50 percent.

A June 22, 2015 MIT news release (also on EurekAlert), which originated the news item, describes some additional capabilities,

Moreover, the researchers’ chip achieves those efficiency improvements while assuming additional responsibilities. Where its predecessors could use a solar cell to either charge a battery or directly power a device, this new chip can do both, and it can power the device directly from the battery.

All of those operations also share a single inductor — the chip’s main electrical component — which saves on circuit board space but increases the circuit complexity even further. Nonetheless, the chip’s power consumption remains low.

“We still want to have battery-charging capability, and we still want to provide a regulated output voltage,” says Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on the new paper. “We need to regulate the input to extract the maximum power, and we really want to do all these tasks with inductor sharing and see which operational mode is the best. And we want to do it without compromising the performance, at very limited input power levels — 10 nanowatts to 1 microwatt — for the Internet of things.”

The prototype chip was manufactured through the Taiwan Semiconductor Manufacturing Company’s University Shuttle Program.

The MIT news release goes on to describe chip specifics,

The circuit’s chief function is to regulate the voltages between the solar cell, the battery, and the device the cell is powering. If the battery operates for too long at a voltage that’s either too high or too low, for instance, its chemical reactants break down, and it loses the ability to hold a charge.

To control the current flow across their chip, El-Damak and her advisor, Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor in Electrical Engineering, use an inductor, which is a wire wound into a coil. When a current passes through an inductor, it generates a magnetic field, which in turn resists any change in the current.

Throwing switches in the inductor’s path causes it to alternately charge and discharge, so that the current flowing through it continuously ramps up and then drops back down to zero. Keeping a lid on the current improves the circuit’s efficiency, since the rate at which it dissipates energy as heat is proportional to the square of the current.

Once the current drops to zero, however, the switches in the inductor’s path need to be thrown immediately; otherwise, current could begin to flow through the circuit in the wrong direction, which would drastically diminish its efficiency. The complication is that the rate at which the current rises and falls depends on the voltage generated by the solar cell, which is highly variable. So the timing of the switch throws has to vary, too.

Electric hourglass

To control the switches’ timing, El-Damak and Chandrakasan use an electrical component called a capacitor, which can store electrical charge. The higher the current, the more rapidly the capacitor fills. When it’s full, the circuit stops charging the inductor.

The rate at which the current drops off, however, depends on the output voltage, whose regulation is the very purpose of the chip. Since that voltage is fixed, the variation in timing has to come from variation in capacitance. El-Damak and Chandrakasan thus equip their chip with a bank of capacitors of different sizes. As the current drops, it charges a subset of those capacitors, whose selection is determined by the solar cell’s voltage. Once again, when the capacitor fills, the switches in the inductor’s path are flipped.

“In this technology space, there’s usually a trend to lower efficiency as the power gets lower, because there’s a fixed amount of energy that’s consumed by doing the work,” says Brett Miwa, who leads a power conversion development project as a fellow at the chip manufacturer Maxim Integrated. “If you’re only coming in with a small amount, it’s hard to get most of it out, because you lose more as a percentage. [El-Damak’s] design is unusually efficient for how low a power level she’s at.”

“One of the things that’s most notable about it is that it’s really a fairly complete system,” he adds. “It’s really kind of a full system-on-a chip for power management. And that makes it a little more complicated, a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature. So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy.”

I wonder how close they are to commercializing this chip (see below),

The MIT researchers' prototype for a chip measuring 3 millimeters by 3 millimeters. The magnified detail shows the chip's main control circuitry, including the startup electronics; the controller that determines whether to charge the battery, power a device, or both; and the array of switches that control current flow to an external inductor coil. This active area measures just 2.2 millimeters by 1.1 millimeters. (click on image to enlarge) Read more: Toward tiny, solar-powered sensors. Courtesy: MIT

The MIT researchers’ prototype for a chip measuring 3 millimeters by 3 millimeters. The magnified detail shows the chip’s main control circuitry, including the startup electronics; the controller that determines whether to charge the battery, power a device, or both; and the array of switches that control current flow to an external inductor coil. This active area measures just 2.2 millimeters by 1.1 millimeters. (click on image to enlarge)
Courtesy: MIT

I sing the body cyber: two projects funded by the US National Science Foundation

Points to anyone who recognized the reference to Walt Whitman’s poem, “I sing the body electric,” from his classic collection, Leaves of Grass (1867 edition; h/t Wikipedia entry). I wonder if the cyber physical systems (CPS) work being funded by the US National Science Foundation (NSF) in the US will occasion poetry too.

More practically, a May 15, 2015 news item on Nanowerk, describes two cyber physical systems (CPS) research projects newly funded by the NSF,

Today [May 12, 2015] the National Science Foundation (NSF) announced two, five-year, center-scale awards totaling $8.75 million to advance the state-of-the-art in medical and cyber-physical systems (CPS).

One project will develop “Cyberheart”–a platform for virtual, patient-specific human heart models and associated device therapies that can be used to improve and accelerate medical-device development and testing. The other project will combine teams of microrobots with synthetic cells to perform functions that may one day lead to tissue and organ re-generation.

CPS are engineered systems that are built from, and depend upon, the seamless integration of computation and physical components. Often called the “Internet of Things,” CPS enable capabilities that go beyond the embedded systems of today.

“NSF has been a leader in supporting research in cyber-physical systems, which has provided a foundation for putting the ‘smart’ in health, transportation, energy and infrastructure systems,” said Jim Kurose, head of Computer & Information Science & Engineering at NSF. “We look forward to the results of these two new awards, which paint a new and compelling vision for what’s possible for smart health.”

Cyber-physical systems have the potential to benefit many sectors of our society, including healthcare. While advances in sensors and wearable devices have the capacity to improve aspects of medical care, from disease prevention to emergency response, and synthetic biology and robotics hold the promise of regenerating and maintaining the body in radical new ways, little is known about how advances in CPS can integrate these technologies to improve health outcomes.

These new NSF-funded projects will investigate two very different ways that CPS can be used in the biological and medical realms.

A May 12, 2015 NSF news release (also on EurekAlert), which originated the news item, describes the two CPS projects,

Bio-CPS for engineering living cells

A team of leading computer scientists, roboticists and biologists from Boston University, the University of Pennsylvania and MIT have come together to develop a system that combines the capabilities of nano-scale robots with specially designed synthetic organisms. Together, they believe this hybrid “bio-CPS” will be capable of performing heretofore impossible functions, from microscopic assembly to cell sensing within the body.

“We bring together synthetic biology and micron-scale robotics to engineer the emergence of desired behaviors in populations of bacterial and mammalian cells,” said Calin Belta, a professor of mechanical engineering, systems engineering and bioinformatics at Boston University and principal investigator on the project. “This project will impact several application areas ranging from tissue engineering to drug development.”

The project builds on previous research by each team member in diverse disciplines and early proof-of-concept designs of bio-CPS. According to the team, the research is also driven by recent advances in the emerging field of synthetic biology, in particular the ability to rapidly incorporate new capabilities into simple cells. Researchers so far have not been able to control and coordinate the behavior of synthetic cells in isolation, but the introduction of microrobots that can be externally controlled may be transformative.

In this new project, the team will focus on bio-CPS with the ability to sense, transport and work together. As a demonstration of their idea, they will develop teams of synthetic cell/microrobot hybrids capable of constructing a complex, fabric-like surface.

Vijay Kumar (University of Pennsylvania), Ron Weiss (MIT), and Douglas Densmore (BU) are co-investigators of the project.

Medical-CPS and the ‘Cyberheart’

CPS such as wearable sensors and implantable devices are already being used to assess health, improve quality of life, provide cost-effective care and potentially speed up disease diagnosis and prevention. [emphasis mine]

Extending these efforts, researchers from seven leading universities and centers are working together to develop far more realistic cardiac and device models than currently exist. This so-called “Cyberheart” platform can be used to test and validate medical devices faster and at a far lower cost than existing methods. CyberHeart also can be used to design safe, patient-specific device therapies, thereby lowering the risk to the patient.

“Innovative ‘virtual’ design methodologies for implantable cardiac medical devices will speed device development and yield safer, more effective devices and device-based therapies, than is currently possible,” said Scott Smolka, a professor of computer science at Stony Brook University and one of the principal investigators on the award.

The group’s approach combines patient-specific computational models of heart dynamics with advanced mathematical techniques for analyzing how these models interact with medical devices. The analytical techniques can be used to detect potential flaws in device behavior early on during the device-design phase, before animal and human trials begin. They also can be used in a clinical setting to optimize device settings on a patient-by-patient basis before devices are implanted.

“We believe that our coordinated, multi-disciplinary approach, which balances theoretical, experimental and practical concerns, will yield transformational results in medical-device design and foundations of cyber-physical system verification,” Smolka said.

The team will develop virtual device models which can be coupled together with virtual heart models to realize a full virtual development platform that can be subjected to computational analysis and simulation techniques. Moreover, they are working with experimentalists who will study the behavior of virtual and actual devices on animals’ hearts.

Co-investigators on the project include Edmund Clarke (Carnegie Mellon University), Elizabeth Cherry (Rochester Institute of Technology), W. Rance Cleaveland (University of Maryland), Flavio Fenton (Georgia Tech), Rahul Mangharam (University of Pennsylvania), Arnab Ray (Fraunhofer Center for Experimental Software Engineering [Germany]) and James Glimm and Radu Grosu (Stony Brook University). Richard A. Gray of the U.S. Food and Drug Administration is another key contributor.

It is fascinating to observe how terminology is shifting from pacemakers and deep brain stimulators as implants to “CPS such as wearable sensors and implantable devices … .” A new category has been created, CPS, which conjoins medical devices with other sensing devices such as wearable fitness monitors found in the consumer market. I imagine it’s an attempt to quell fears about injecting strange things into or adding strange things to your body—microrobots and nanorobots partially derived from synthetic biology research which are “… capable of performing heretofore impossible functions, from microscopic assembly to cell sensing within the body.” They’ve also sneaked in a reference to synthetic biology, an area of research where some concerns have been expressed, from my March 19, 2013 post about a poll and synthetic biology concerns,

In our latest survey, conducted in January 2013, three-fourths of respondents say they have heard little or nothing about synthetic biology, a level consistent with that measured in 2010. While initial impressions about the science are largely undefined, these feelings do not necessarily become more positive as respondents learn more. The public has mixed reactions to specific synthetic biology applications, and almost one-third of respondents favor a ban “on synthetic biology research until we better understand its implications and risks,” while 61 percent think the science should move forward.

I imagine that for scientists, 61% in favour of more research is not particularly comforting given how easily and quickly public opinion can shift.

Sealing graphene’s defects to make a better filtration device

Making a graphene filter that allows water to pass through while screening out salt and/or noxious materials has been more challenging than one might think. According to a May 7, 2015 news item on Nanowerk, graphene filters can be ‘leaky’,

For faster, longer-lasting water filters, some scientists are looking to graphene –thin, strong sheets of carbon — to serve as ultrathin membranes, filtering out contaminants to quickly purify high volumes of water.

Graphene’s unique properties make it a potentially ideal membrane for water filtration or desalination. But there’s been one main drawback to its wider use: Making membranes in one-atom-thick layers of graphene is a meticulous process that can tear the thin material — creating defects through which contaminants can leak.

Now engineers at MIT [Massachusetts Institute of Technology], Oak Ridge National Laboratory, and King Fahd University of Petroleum and Minerals (KFUPM) have devised a process to repair these leaks, filling cracks and plugging holes using a combination of chemical deposition and polymerization techniques. The team then used a process it developed previously to create tiny, uniform pores in the material, small enough to allow only water to pass through.

A May 8, 2015 MIT news release (also on EurkeAlert), which originated the news item, expands on the theme,

Combining these two techniques, the researchers were able to engineer a relatively large defect-free graphene membrane — about the size of a penny. The membrane’s size is significant: To be exploited as a filtration membrane, graphene would have to be manufactured at a scale of centimeters, or larger.

In experiments, the researchers pumped water through a graphene membrane treated with both defect-sealing and pore-producing processes, and found that water flowed through at rates comparable to current desalination membranes. The graphene was able to filter out most large-molecule contaminants, such as magnesium sulfate and dextran.

Rohit Karnik, an associate professor of mechanical engineering at MIT, says the group’s results, published in the journal Nano Letters, represent the first success in plugging graphene’s leaks.

“We’ve been able to seal defects, at least on the lab scale, to realize molecular filtration across a macroscopic area of graphene, which has not been possible before,” Karnik says. “If we have better process control, maybe in the future we don’t even need defect sealing. But I think it’s very unlikely that we’ll ever have perfect graphene — there will always be some need to control leakages. These two [techniques] are examples which enable filtration.”

Sean O’Hern, a former graduate research assistant at MIT, is the paper’s first author. Other contributors include MIT graduate student Doojoon Jang, former graduate student Suman Bose, and Professor Jing Kong.

A delicate transfer

“The current types of membranes that can produce freshwater from saltwater are fairly thick, on the order of 200 nanometers,” O’Hern says. “The benefit of a graphene membrane is, instead of being hundreds of nanometers thick, we’re on the order of three angstroms — 600 times thinner than existing membranes. This enables you to have a higher flow rate over the same area.”

O’Hern and Karnik have been investigating graphene’s potential as a filtration membrane for the past several years. In 2009, the group began fabricating membranes from graphene grown on copper — a metal that supports the growth of graphene across relatively large areas. However, copper is impermeable, requiring the group to transfer the graphene to a porous substrate following fabrication.

However, O’Hern noticed that this transfer process would create tears in graphene. What’s more, he observed intrinsic defects created during the growth process, resulting perhaps from impurities in the original material.

Plugging graphene’s leaks

To plug graphene’s leaks, the team came up with a technique to first tackle the smaller intrinsic defects, then the larger transfer-induced defects. For the intrinsic defects, the researchers used a process called “atomic layer deposition,” placing the graphene membrane in a vacuum chamber, then pulsing in a hafnium-containing chemical that does not normally interact with graphene. However, if the chemical comes in contact with a small opening in graphene, it will tend to stick to that opening, attracted by the area’s higher surface energy.

The team applied several rounds of atomic layer deposition, finding that the deposited hafnium oxide successfully filled in graphene’s nanometer-scale intrinsic defects. However, O’Hern realized that using the same process to fill in much larger holes and tears — on the order of hundreds of nanometers — would require too much time.

Instead, he and his colleagues came up with a second technique to fill in larger defects, using a process called “interfacial polymerization” that is often employed in membrane synthesis. After they filled in graphene’s intrinsic defects, the researchers submerged the membrane at the interface of two solutions: a water bath and an organic solvent that, like oil, does not mix with water.

In the two solutions, the researchers dissolved two different molecules that can react to form nylon. Once O’Hern placed the graphene membrane at the interface of the two solutions, he observed that nylon plugs formed only in tears and holes — regions where the two molecules could come in contact because of tears in the otherwise impermeable graphene — effectively sealing the remaining defects.

Using a technique they developed last year, the researchers then etched tiny, uniform holes in graphene — small enough to let water molecules through, but not larger contaminants. In experiments, the group tested the membrane with water containing several different molecules, including salt, and found that the membrane rejected up to 90 percent of larger molecules. However, it let salt through at a faster rate than water.

The preliminary tests suggest that graphene may be a viable alternative to existing filtration membranes, although Karnik says techniques to seal its defects and control its permeability will need further improvements.

“Water desalination and nanofiltration are big applications where, if things work out and this technology withstands the different demands of real-world tests, it would have a large impact,” Karnik says. “But one could also imagine applications for fine chemical- or biological-sample processing, where these membranes could be useful. And this is the first report of a centimeter-scale graphene membrane that does any kind of molecular filtration. That’s exciting.”

De-en Jiang, an assistant professor of chemistry at the University of California at Riverside, sees the defect-sealing technique as “a great advance toward making graphene filtration a reality.”

“The two-step technique is very smart: sealing the defects while preserving the desired pores for filtration,” says Jiang, who did not contribute to the research. “This would make the scale-up much easier. One can produce a large graphene membrane first, not worrying about the defects, which can be sealed later.”

I have featured graphene and water desalination work before  from these researchers at MIT in a Feb. 27, 2014 posting. Interestingly, there was no mention of problems with defects in the news release highlighting this previous work.

Here’s a link to and a citation for the latest paper,

Nanofiltration across Defect-Sealed Nanoporous Monolayer Graphene by Sean C. O’Hern, Doojoon Jang, Suman Bose, Juan-Carlos Idrobo, Yi Song §, Tahar Laoui, Jing Kong, and Rohit Karnik. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b00456 Publication Date (Web): April 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Carbon nanotubes sense spoiled food


Courtesy: MIT (Massachusetts Institute of Technology)

I love this .gif; it says a lot without a word. However for details, you need words and here’s what an April 15, 2015 news item on Nanowerk has to say about the research illustrated by the .gif,

MIT [Massachusetts Institute of Technology] chemists have devised an inexpensive, portable sensor that can detect gases emitted by rotting meat, allowing consumers to determine whether the meat in their grocery store or refrigerator is safe to eat.

The sensor, which consists of chemically modified carbon nanotubes, could be deployed in “smart packaging” that would offer much more accurate safety information than the expiration date on the package, says Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT.

An April 14, 2015 MIT news release (also on EurekAlert), which originated the news item, offers more from Dr. Swager,

It could also cut down on food waste, he adds. “People are constantly throwing things out that probably aren’t bad,” says Swager, who is the senior author of a paper describing the new sensor this week in the journal Angewandte Chemie.

This latest study is builds on previous work at Swager’s lab (Note: Links have been removed),

The sensor is similar to other carbon nanotube devices that Swager’s lab has developed in recent years, including one that detects the ripeness of fruit. All of these devices work on the same principle: Carbon nanotubes can be chemically modified so that their ability to carry an electric current changes in the presence of a particular gas.

In this case, the researchers modified the carbon nanotubes with metal-containing compounds called metalloporphyrins, which contain a central metal atom bound to several nitrogen-containing rings. Hemoglobin, which carries oxygen in the blood, is a metalloporphyrin with iron as the central atom.

For this sensor, the researchers used a metalloporphyrin with cobalt at its center. Metalloporphyrins are very good at binding to nitrogen-containing compounds called amines. Of particular interest to the researchers were the so-called biogenic amines, such as putrescine and cadaverine, which are produced by decaying meat.

When the cobalt-containing porphyrin binds to any of these amines, it increases the electrical resistance of the carbon nanotube, which can be easily measured.

“We use these porphyrins to fabricate a very simple device where we apply a potential across the device and then monitor the current. When the device encounters amines, which are markers of decaying meat, the current of the device will become lower,” Liu says.

In this study, the researchers tested the sensor on four types of meat: pork, chicken, cod, and salmon. They found that when refrigerated, all four types stayed fresh over four days. Left unrefrigerated, the samples all decayed, but at varying rates.

There are other sensors that can detect the signs of decaying meat, but they are usually large and expensive instruments that require expertise to operate. “The advantage we have is these are the cheapest, smallest, easiest-to-manufacture sensors,” Swager says.

“There are several potential advantages in having an inexpensive sensor for measuring, in real time, the freshness of meat and fish products, including preventing foodborne illness, increasing overall customer satisfaction, and reducing food waste at grocery stores and in consumers’ homes,” says Roberto Forloni, a senior science fellow at Sealed Air, a major supplier of food packaging, who was not part of the research team.

The new device also requires very little power and could be incorporated into a wireless platform Swager’s lab recently developed that allows a regular smartphone to read output from carbon nanotube sensors such as this one.

The funding sources are interesting, as I am appreciating with increasing frequency these days (from the news release),

The researchers have filed for a patent on the technology and hope to license it for commercial development. The research was funded by the National Science Foundation and the Army Research Office through MIT’s Institute for Soldier Nanotechnologies.

Here’s a link to and a citation for the paper,

Single-Walled Carbon Nanotube/Metalloporphyrin Composites for the Chemiresistive Detection of Amines and Meat Spoilage by Sophie F. Liu, Alexander R. Petty, Dr. Graham T. Sazama, and Timothy M. Swager. Angewandte Chemie International Edition DOI: 10.1002/anie.201501434 Article first published online: 13 APR 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

There are other posts here about the quest to create food sensors including this Sept. 26, 2013 piece which features a critique (by another blogger) about trying to create food sensors that may be more expensive than the item they are protecting, a problem Swager claims to have overcome in an April 17, 2015 article by Ben Schiller for Fast Company (Note: Links have been removed),

Swager has set up a company to commercialize the technology and he expects to do the first demonstrations to interested clients this summer. The first applications are likely to be for food workers working with meat and fish, but there’s no reason why consumers shouldn’t get their own devices in due time.

There are efforts to create visual clues for food status. But Swager says his method is better because it doesn’t rely on perception: it produces hard data that can be logged and tracked. And it also has potential to be very cheap.

“The resistance method is a game-changer because it’s two to three orders of magnitude cheaper than other technology. It’s hard to imagine doing this cheaper,” he says.

Taking the baking out of aircraft manufacture

It seems that ovens are an essential piece of equipment when manufacturing aircraft parts but that may change if research from MIT (Massachusetts Institute of Technology) proves successful. An April 14, 2015 news item on ScienceDaily describes the current process and the MIT research,

Composite materials used in aircraft wings and fuselages are typically manufactured in large, industrial-sized ovens: Multiple polymer layers are blasted with temperatures up to 750 degrees Fahrenheit, and solidified to form a solid, resilient material. Using this approach, considerable energy is required first to heat the oven, then the gas around it, and finally the actual composite.

Aerospace engineers at MIT have now developed a carbon nanotube (CNT) film that can heat and solidify a composite without the need for massive ovens. When connected to an electrical power source, and wrapped over a multilayer polymer composite, the heated film stimulates the polymer to solidify.

The group tested the film on a common carbon-fiber material used in aircraft components, and found that the film created a composite as strong as that manufactured in conventional ovens — while using only 1 percent of the energy.

The new “out-of-oven” approach may offer a more direct, energy-saving method for manufacturing virtually any industrial composite, says Brian L. Wardle, an associate professor of aeronautics and astronautics at MIT.

“Typically, if you’re going to cook a fuselage for an Airbus A350 or Boeing 787, you’ve got about a four-story oven that’s tens of millions of dollars in infrastructure that you don’t need,” Wardle says. “Our technique puts the heat where it is needed, in direct contact with the part being assembled. Think of it as a self-heating pizza. … Instead of an oven, you just plug the pizza into the wall and it cooks itself.”

Wardle says the carbon nanotube film is also incredibly lightweight: After it has fused the underlying polymer layers, the film itself — a fraction of a human hair’s diameter — meshes with the composite, adding negligible weight.

An April 14, 2015 MIT news release, which originated the news item, describes the origins of the team’s latest research, the findings, and the implications,

Carbon nanotube deicers

Wardle and his colleagues have experimented with CNT films in recent years, mainly for deicing airplane wings. The team recognized that in addition to their negligible weight, carbon nanotubes heat efficiently when exposed to an electric current.

The group first developed a technique to create a film of aligned carbon nanotubes composed of tiny tubes of crystalline carbon, standing upright like trees in a forest. The researchers used a rod to roll the “forest” flat, creating a dense film of aligned carbon nanotubes.

In experiments, Wardle and his team integrated the film into airplane wings via conventional, oven-based curing methods, showing that when voltage was applied, the film generated heat, preventing ice from forming.

The deicing tests inspired a question: If the CNT film could generate heat, why not use it to make the composite itself?

How hot can you go?

In initial experiments, the researchers investigated the film’s potential to fuse two types of aerospace-grade composite typically used in aircraft wings and fuselages. Normally the material, composed of about 16 layers, is solidified, or cross-linked, in a high-temperature industrial oven.

The researchers manufactured a CNT film about the size of a Post-It note, and placed the film over a square of Cycom 5320-1. They connected electrodes to the film, then applied a current to heat both the film and the underlying polymer in the Cycom composite layers.

The team measured the energy required to solidify, or cross-link, the polymer and carbon fiber layers, finding that the CNT film used one-hundredth the electricity required for traditional oven-based methods to cure the composite. Both methods generated composites with similar properties, such as cross-linking density.

Wardle says the results pushed the group to test the CNT film further: As different composites require different temperatures in order to fuse, the researchers looked to see whether the CNT film could, quite literally, take the heat.

“At some point, heaters fry out,” Wardle says. “They oxidize, or have different ways in which they fail. What we wanted to see was how hot could this material go.”

To do this, the group tested the film’s ability to generate higher and higher temperatures, and found it topped out at over 1,000 F. In comparison, some of the highest-temperature aerospace polymers require temperatures up to 750 F in order to solidify.

“We can process at those temperatures, which means there’s no composite we can’t process,” Wardle says. “This really opens up all polymeric materials to this technology.”

The team is working with industrial partners to find ways to scale up the technology to manufacture composites large enough to make airplane fuselages and wings.

“There needs to be some thought given to electroding, and how you’re going to actually make the electrical contact efficiently over very large areas,” Wardle says. “You’d need much less power than you are currently putting into your oven. I don’t think it’s a challenge, but it has to be done.”

Gregory Odegard, a professor of computational mechanics at Michigan Technological University, says the group’s carbon nanotube film may go toward improving the quality and efficiency of fabrication processes for large composites, such as wings on commercial aircraft. The new technique may also open the door to smaller firms that lack access to large industrial ovens.

“Smaller companies that want to fabricate composite parts may be able to do so without investing in large ovens or outsourcing,” says Odegard, who was not involved in the research. “This could lead to more innovation in the composites sector, and perhaps improvements in the performance and usage of composite materials.”

It can be interesting to find out who funds the research (from the news release),

This research was funded in part by Airbus Group, Boeing, Embraer, Lockheed Martin, Saab AB, TohoTenax, ANSYS Inc., the Air Force Research Laboratory at Wright-Patterson Air Force Base, and the U.S. Army Research Office.

Here’s a link to and citation for the research paper,

Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks by Jeonyoon Lee, Itai Y. Stein, Mackenzie E. Devoe, Diana J. Lewis, Noa Lachman, Seth S. Kessler, Samuel T. Buschhorn, and Brian L. Wardle. Appl. Phys. Lett. 106, 053110 (2015); http://dx.doi.org/10.1063/1.4907608

This paper is behind a paywall.

Entangling thousands of atoms

Quantum entanglement as an idea seems extraordinary to me like something from of the fevered imagination made possible only with certain kinds of hallucinogens. I suppose you could call theoretical physicists who’ve conceptualized entanglement a different breed as they don’t seem to need chemical assistance for their flights of fancy, which turn out to be reality. Researchers at MIT (Massachusetts Institute of Technology) and the University of Belgrade (Serbia) have entangled thousands of atoms with a single photon according to a March 26, 2015 news item on Nanotechnology Now,

Physicists from MIT and the University of Belgrade have developed a new technique that can successfully entangle 3,000 atoms using only a single photon. The results, published today in the journal Nature, represent the largest number of particles that have ever been mutually entangled experimentally.

The researchers say the technique provides a realistic method to generate large ensembles of entangled atoms, which are key components for realizing more-precise atomic clocks.

“You can make the argument that a single photon cannot possibly change the state of 3,000 atoms, but this one photon does — it builds up correlations that you didn’t have before,” says Vladan Vuletic, the Lester Wolfe Professor in MIT’s Department of Physics, and the paper’s senior author. “We have basically opened up a new class of entangled states we can make, but there are many more new classes to be explored.”

A March 26, 2015 MIT news release by Jennifer Chu (also on EurekAlert but dated March 25, 2015), which originated the news item, describes entanglement with particular attention to how it relates to atomic timekeeping,

Entanglement is a curious phenomenon: As the theory goes, two or more particles may be correlated in such a way that any change to one will simultaneously change the other, no matter how far apart they may be. For instance, if one atom in an entangled pair were somehow made to spin clockwise, the other atom would instantly be known to spin counterclockwise, even though the two may be physically separated by thousands of miles.

The phenomenon of entanglement, which physicist Albert Einstein once famously dismissed as “spooky action at a distance,” is described not by the laws of classical physics, but by quantum mechanics, which explains the interactions of particles at the nanoscale. At such minuscule scales, particles such as atoms are known to behave differently from matter at the macroscale.

Scientists have been searching for ways to entangle not just pairs, but large numbers of atoms; such ensembles could be the basis for powerful quantum computers and more-precise atomic clocks. The latter is a motivation for Vuletic’s group.

Today’s best atomic clocks are based on the natural oscillations within a cloud of trapped atoms. As the atoms oscillate, they act as a pendulum, keeping steady time. A laser beam within the clock, directed through the cloud of atoms, can detect the atoms’ vibrations, which ultimately determine the length of a single second.

“Today’s clocks are really amazing,” Vuletic says. “They would be less than a minute off if they ran since the Big Bang — that’s the stability of the best clocks that exist today. We’re hoping to get even further.”

The accuracy of atomic clocks improves as more and more atoms oscillate in a cloud. Conventional atomic clocks’ precision is proportional to the square root of the number of atoms: For example, a clock with nine times more atoms would only be three times as accurate. If these same atoms were entangled, a clock’s precision could be directly proportional to the number of atoms — in this case, nine times as accurate. The larger the number of entangled particles, then, the better an atomic clock’s timekeeping.

It seems weak lasers make big entanglements possible (from the news release),

Scientists have so far been able to entangle large groups of atoms, although most attempts have only generated entanglement between pairs in a group. Only one team has successfully entangled 100 atoms — the largest mutual entanglement to date, and only a small fraction of the whole atomic ensemble.

Now Vuletic and his colleagues have successfully created a mutual entanglement among 3,000 atoms, virtually all the atoms in the ensemble, using very weak laser light — down to pulses containing a single photon. The weaker the light, the better, Vuletic says, as it is less likely to disrupt the cloud. “The system remains in a relatively clean quantum state,” he says.

The researchers first cooled a cloud of atoms, then trapped them in a laser trap, and sent a weak laser pulse through the cloud. They then set up a detector to look for a particular photon within the beam. Vuletic reasoned that if a photon has passed through the atom cloud without event, its polarization, or direction of oscillation, would remain the same. If, however, a photon has interacted with the atoms, its polarization rotates just slightly — a sign that it was affected by quantum “noise” in the ensemble of spinning atoms, with the noise being the difference in the number of atoms spinning clockwise and counterclockwise.

“Every now and then, we observe an outgoing photon whose electric field oscillates in a direction perpendicular to that of the incoming photons,” Vuletic says. “When we detect such a photon, we know that must have been caused by the atomic ensemble, and surprisingly enough, that detection generates a very strongly entangled state of the atoms.”

Vuletic and his colleagues are currently using the single-photon detection technique to build a state-of-the-art atomic clock that they hope will overcome what’s known as the “standard quantum limit” — a limit to how accurate measurements can be in quantum systems. Vuletic says the group’s current setup may be a step toward developing even more complex entangled states.

“This particular state can improve atomic clocks by a factor of two,” Vuletic says. “We’re striving toward making even more complicated states that can go further.”

This research was supported in part by the National Science Foundation, the Defense Advanced Research Projects Agency, and the Air Force Office of Scientific Research.

Here’s a link to and a citation for the paper,

Entanglement with negative Wigner function of almost 3,000 atoms heralded by one photon by Robert McConnell, Hao Zhang, Jiazhong Hu, Senka Ćuk & Vladan Vuletić. Nature 519 439–442 (26 March 2015) doi:10.1038/nature14293 Published online 25 March 2015

This article is behind a paywall but there is a free preview via ReadCube Access.

This image illustrates the entanglement of a large number of atoms. The atoms, shown in purple, are shown mutually entangled with one another. Image: Christine Daniloff/MIT and Jose-Luis Olivares/MIT

This image illustrates the entanglement of a large number of atoms. The atoms, shown in purple, are shown mutually entangled with one another.
Image: Christine Daniloff/MIT and Jose-Luis Olivares/MIT

Blue-striped limpets and their nanophotonic features

This is a structural colour story limpets and the Massachusetts Institute of Technology (MIT) and Harvard University. For the impatient here’s a video summary of the work courtesy of the researchers,

A Feb. 26, 2015 news item on ScienceDaily reiterates the details for those who like to read their science,

The blue-rayed limpet is a tiny mollusk that lives in kelp beds along the coasts of Norway, Iceland, the United Kingdom, Portugal, and the Canary Islands. These diminutive organisms — as small as a fingernail — might escape notice entirely, if not for a very conspicuous feature: bright blue dotted lines that run in parallel along the length of their translucent shells. Depending on the angle at which light hits, a limpet’s shell can flash brilliantly even in murky water.

Now scientists at MIT and Harvard University have identified two optical structures within the limpet’s shell that give its blue-striped appearance. The structures are configured to reflect blue light while absorbing all other wavelengths of incoming light. The researchers speculate that such patterning may have evolved to protect the limpet, as the blue lines resemble the color displays on the shells of more poisonous soft-bodied snails.

A Feb. 26, 2015 MIT news release (also on EurekAlert), which originated the news item, explains why this discovery is special,

The findings, reported this week in the journal Nature Communications, represent the first evidence of an organism using mineralized structural components to produce optical displays. While birds, butterflies, and beetles can display brilliant blues, among other colors, they do so with organic structures, such as feathers, scales, and plates. The limpet, by contrast, produces its blue stripes through an interplay of inorganic, mineral structures, arranged in such a way as to reflect only blue light.

The researchers say such natural optical structures may serve as a design guide for engineering color-selective, controllable, transparent displays that require no internal light source and could be incorporated into windows and glasses.

“Let’s imagine a window surface in a car where you obviously want to see the outside world as you’re driving, but where you also can overlay the real world with an augmented reality that could involve projecting a map and other useful information on the world that exists on the other side of the windshield,” says co-author Mathias Kolle, an assistant professor of mechanical engineering at MIT. “We believe that the limpet’s approach to displaying color patterns in a translucent shell could serve as a starting point for developing such displays.”

The news release then reveals how this research came about,

Kolle, whose research is focused on engineering bioinspired, optical materials — including color-changing, deformable fibers — started looking into the optical features of the limpet when his brother Stefan, a marine biologist now working at Harvard, brought Kolle a few of the organisms in a small container. Stefan Kolle was struck by the mollusk’s brilliant patterning, and recruited his brother, along with several others, to delve deeper into the limpet shell’s optical properties.

To do this, the team of researchers — which also included Ling Li and Christine Ortiz at MIT and James Weaver and Joanna Aizenberg at Harvard — performed a detailed structural and optical analysis of the limpet shells. They observed that the blue stripes first appear in juveniles, resembling dashed lines. The stripes grow more continuous as a limpet matures, and their shade varies from individual to individual, ranging from deep blue to turquoise.

The researchers scanned the surface of a limpet’s shell using scanning electron microscopy, and found no structural differences in areas with and without the stripes — an observation that led them to think that perhaps the stripes arose from features embedded deeper in the shell.

To get a picture of what lay beneath, the researchers used a combination of high-resolution 2-D and 3-D structural analysis to reveal the 3-D nanoarchitecture of the photonic structures embedded in the limpets’ translucent shells.

What they found was revealing: In the regions with blue stripes, the shells’ top and bottom layers were relatively uniform, with dense stacks of calcium carbonate platelets and thin organic layers, similar to the shell structure of other mollusks. However, about 30 microns beneath the shell surface the researchers noted a stark difference. In these regions, the researchers found that the regular plates of calcium carbonate morphed into two distinct structural features: a multilayered structure with regular spacing between calcium carbonate layers resembling a zigzag pattern, and beneath this, a layer of randomly dispersed, spherical particles.

The researchers measured the dimensions of the zigzagging plates, and found the spacing between them was much wider than the more uniform plates running through the shell’s unstriped sections. They then examined the potential optical roles of both the multilayer zigzagging structure and the spherical particles.

Kolle and his colleagues used optical microscopy, spectroscopy, and diffraction microscopy to quantify the blue stripe’s light-reflection properties. They then measured the zigzagging structures and their angle with respect to the shell surface, and determined that this structure is optimized to reflect blue and green light.

The researchers also determined that the disordered arrangement of spherical particles beneath the zigzag structures serves to absorb transmitted light that otherwise could de-saturate the reflected blue color.

From these results, Kolle and his team deduced that the zigzag pattern acts as a filter, reflecting only blue light. As the rest of the incoming light passes through the shell, the underlying particles absorb this light — an effect that makes a shell’s stripes appear even more brilliantly blue.

And, for those who can never get enough detail, the news release provides a bit more than the video,

The team then sought to tackle a follow-up question: What purpose do the blue stripes serve? The limpets live either concealed at the base of kelp plants, or further up in the fronds, where they are visually exposed. Those at the base grow a thicker shell with almost no stripes, while their blue-striped counterparts live higher on the plant.

Limpets generally don’t have well-developed eyes, so the researchers reasoned that the blue stripes must not serve as a communication tool, attracting one organism to another. Rather, they think that the limpet’s stripes may be a defensive mechanism: The mollusk sits largely exposed on a frond, so a plausible defense against predators may be to appear either invisible or unappetizing. The researchers determined that the latter is more likely the case, as the limpet’s blue stripes resemble the patterning of poisonous marine snails that also happen to inhabit similar kelp beds.

Kolle says the group’s work has revealed an interesting insight into the limpet’s optical properties, which may be exploited to engineer advanced transparent optical displays. The limpet, he points out, has evolved a microstructure in its shell to satisfy an optical purpose without overly compromising the shell’s mechanical integrity. Materials scientists and engineers could take inspiration from this natural balancing act.

“It’s all about multifunctional materials in nature: Every organism — no matter if it has a shell, or skin, or feathers — interacts in various ways with the environment, and the materials with which it interfaces to the outside world frequently have to fulfill multiple functions simultaneously,” Kolle says. “[Engineers] are more and more focusing on not only optimizing just one single property in a material or device, like a brighter screen or higher pixel density, but rather on satisfying several … design and performance criteria simultaneously. We can gain inspiration and insight from nature.”

Peter Vukusic, an associate professor of physics at the University of Exeter in the United Kingdom, says the researchers “have done an exquisite job” in uncovering the optical mechanism behind the limpet’s conspicuous appearance.

“By using multiple and complementary analysis techniques they have elucidated, in glorious detail, the many structural and physiological factors that have given rise to the optical signature of this highly evolved system,” says Vukusic, who was not involved in the study. “The animal’s complex morphology is highly interesting for photonics scientists and technologists interested in manipulating light and creating specialized appearances.”

Here’s a link to and a citation for the paper,

A highly conspicuous mineralized composite photonic architecture in the translucent shell of the blue-rayed limpet by Ling Li, Stefan Kolle, James C. Weaver, Christine Ortiz, Joanna Aizenberg & Mathias Kolle. Nature Communications 6, Article number: 6322 doi:10.1038/ncomms7322 Published 26 February 2015

This article is open access.

MIT (Massachusetts Institute of Technology) signs agreement with Mexican university, Tecnológico de Monterrey

The deal signed by the Massachusetts Institute of Technology (MIT) and one of the largest universities in Latin America covers a five-year period and its initial focus is on nanoscience and nanotechnology. From a Nov. 3, 2014 news item on Azonano,

MIT has established a formal relationship with Tecnológico de Monterrey, one of Latin America’s largest universities, to bring students and faculty from Mexico to Cambridge [Massachusetts, US] for fellowships, internships, and research stays in MIT labs and centers. The agreement will initially focus on research at the frontier of nanoscience and nanotechnology.

An Oct. 31, 2014 MIT news release, which originated the news item, describes the deal and the longstanding relationship between the two institutions,

The agreement was celebrated today with a signing ceremony at MIT attended by a delegation from Tecnológico de Monterrey that included President Salvador Alva; the chairman of the board of trustees, José Antonio Fernández Carbajal; Mexico’s ambassador to the United States, Eduardo Medina Mora; and Daniel Hernández Joseph, the consul general of Mexico in Boston.

“We feel honored for the confidence that the MIT community has placed in us,” Alva says. “Our goal is to educate even more entrepreneurial leaders with the capacity and the motivation to solve humanity’s grand challenges. Leaders capable of creating and sustaining economic and social value. Leaders that will transform the lives of millions of people.”

The agreement sets the stage for increasing long-term cooperation and collaboration between the two universities with an initial academic program that will enable undergraduates, graduate students, postdocs, and junior faculty from Tecnológico de Monterrey to visit the MIT campus, where they will be embedded in labs and centers alongside MIT faculty and students. The participants will gain direct experience in disciplines and topics that match their interests. The program may change or expand its focus after five years.

“The goal for the first five years is to provide students and scholars from Tecnológico de Monterrey with a world-class research experience in nanoscience and nanotechnology and to accelerate research programs of critical importance to Mexico and the world,” says Jesús del Álamo, the Donner Professor of Electrical Engineering, who will coordinate the program at MIT. “And because faculty hosts of participants in the initial program will be recruited from any MIT academic department with relevant activities, we will be able to accommodate interests in nanoscale research over a very broad intellectual front.”

MIT is currently constructing a new facility, MIT.nano, that will be a key resource for future extensions of the program. The new 200,000-square-foot facility, which is being constructed on the site of Building 12 at the center of the MIT campus, will house state-of-the-art cleanroom, imaging, and prototyping facilities supporting research with nanoscale materials and processes — in fields including energy, health, life sciences, quantum sciences, electronics, and manufacturing.

In honor of the new relationship, the facility’s Computer-Aided Visualization Environment will be named after Tecnológico de Monterrey, says Vladimir Bulović, the Fariborz Maseeh Chair in Emerging Technology and faculty lead for the MIT.nano building project.

“When it is completed, MIT.nano will enable students and faculty from Tecnológico de Monterrey to learn and work in one of the most advanced facilities in the world and will give them invaluable experience at the forefront of innovation,” says Bulović, who is also the associate dean for innovation in MIT’s School of Engineering and co-chair of the MIT Innovation Initiative.

Tecnológico de Monterrey is one of the largest universities in Latin America, with nearly 100,000 high school, undergraduate, and graduate students; 31 campuses in Mexico; and 19 international locations and branches in the Americas, Europe, and Japan. This week’s agreement establishes a new relationship between MIT and Tecnológico de Monterrey, but the two institutions have a shared history.

Tecnológico de Monterrey was founded in 1943 by Eugenio Garza Sada, who graduated from MIT in 1914 with a degree in civil engineering. After studying at MIT, Garza Sada — with his brother, Roberto, who graduated from MIT in 1918 — grew his family’s brewery in Mexico into a company that today is known as FEMSA, the largest beverage company in Mexico and Latin America. Tecnológico de Monterrey’s founding director-general was León Ávalos Vez, a mechanical engineer from the MIT Class of 1929.

“We believe that both MIT and Tecnológico de Monterrey play a leadership role in shaping minds and creating knowledge, in serving as catalysts for innovation, entrepreneurship and economic growth, but they also have a responsibility to address the critical problems in the world,” says Fernández, the chairman of the board of trustees at Tecnológico de Monterrey. “This agreement will encourage the implementation of educational programs and accelerate research in nanotechnology in ways that will truly make a difference.”

The new program will commence next spring, with the first students and faculty targeted to come to MIT next summer [2015].

It’ll be interesting to note if this exchange ever reverses and MIT students start visiting Tecnológico de Monterrey campuses. It seems there’s a quite a selection with 31 in Mexico and 19 in various locations internationally.

Silver nanoparticles: liquid on the outside, crystal on the inside

Research from the Massachusetts Institute of Technology (MIT) has revealed a new property of metal nanoparticles, in this case, silver. From an Oct. 12, 2014 news item on ScienceDaily,

A surprising phenomenon has been found in metal nanoparticles: They appear, from the outside, to be liquid droplets, wobbling and readily changing shape, while their interiors retain a perfectly stable crystal configuration.

The research team behind the finding, led by MIT professor Ju Li, says the work could have important implications for the design of components in nanotechnology, such as metal contacts for molecular electronic circuits.

The results, published in the journal Nature Materials, come from a combination of laboratory analysis and computer modeling, by an international team that included researchers in China, Japan, and Pittsburgh, as well as at MIT.

An Oct. 12, 2014 MIT news release (also on EurekAlert), which originated the news item, offers both more information about the research and a surprising comparison of nanometers to the width of a human hair,

The experiments were conducted at room temperature, with particles of pure silver less than 10 nanometers across — less than one-thousandth of the width of a human hair. [emphasis mine] But the results should apply to many different metals, says Li, senior author of the paper and the BEA Professor of Nuclear Science and Engineering.

Silver has a relatively high melting point — 962 degrees Celsius, or 1763 degrees Fahrenheit — so observation of any liquidlike behavior in its nanoparticles was “quite unexpected,” Li says. Hints of the new phenomenon had been seen in earlier work with tin, which has a much lower melting point, he says.

The use of nanoparticles in applications ranging from electronics to pharmaceuticals is a lively area of research; generally, Li says, these researchers “want to form shapes, and they want these shapes to be stable, in many cases over a period of years.” So the discovery of these deformations reveals a potentially serious barrier to many such applications: For example, if gold or silver nanoligaments are used in electronic circuits, these deformations could quickly cause electrical connections to fail.

It was a bit surprising to see the reference to 10 nanometers as being less than 1/1,000th (one/one thousandth) of the width of a human hair in a news release from MIT. Generally, a nanometer has been described as being anywhere from less than 1/50,000th to 1/120,000th of the width of a human hair with less than 1/100,000th being one of the most common descriptions. While it’s true that 10 nanometers is less than 1/1,000th of the width of a human hair, it seems a bit misleading when it could be described, in keeping with the more common description, as less than 1/10,000th.

Getting back to the research, the news release offers more details as to how it was conducted,

The researchers’ detailed imaging with a transmission electron microscope and atomistic modeling revealed that while the exterior of the metal nanoparticles appears to move like a liquid, only the outermost layers — one or two atoms thick — actually move at any given time. As these outer layers of atoms move across the surface and redeposit elsewhere, they give the impression of much greater movement — but inside each particle, the atoms stay perfectly lined up, like bricks in a wall.

“The interior is crystalline, so the only mobile atoms are the first one or two monolayers,” Li says. “Everywhere except the first two layers is crystalline.”

By contrast, if the droplets were to melt to a liquid state, the orderliness of the crystal structure would be eliminated entirely — like a wall tumbling into a heap of bricks.

Technically, the particles’ deformation is pseudoelastic, meaning that the material returns to its original shape after the stresses are removed — like a squeezed rubber ball — as opposed to plasticity, as in a deformable lump of clay that retains a new shape.

The phenomenon of plasticity by interfacial diffusion was first proposed by Robert L. Coble, a professor of ceramic engineering at MIT, and is known as “Coble creep.” “What we saw is aptly called Coble pseudoelasticity,” Li says.

Now that the phenomenon has been understood, researchers working on nanocircuits or other nanodevices can quite easily compensate for it, Li says. If the nanoparticles are protected by even a vanishingly thin layer of oxide, the liquidlike behavior is almost completely eliminated, making stable circuits possible.

There are some benefits to this insight (from the news release),

On the other hand, for some applications this phenomenon might be useful: For example, in circuits where electrical contacts need to withstand rotational reconfiguration, particles designed to maximize this effect might prove useful, using noble metals or a reducing atmosphere, where the formation of an oxide layer is destabilized, Li says.

The new finding flies in the face of expectations — in part, because of a well-understood relationship, in most materials, in which mechanical strength increases as size is reduced.

“In general, the smaller the size, the higher the strength,” Li says, but “at very small sizes, a material component can get very much weaker. The transition from ‘smaller is stronger’ to ‘smaller is much weaker’ can be very sharp.”

That crossover, he says, takes place at about 10 nanometers at room temperature — a size that microchip manufacturers are approaching as circuits shrink. When this threshold is reached, Li says, it causes “a very precipitous drop” in a nanocomponent’s strength.

The findings could also help explain a number of anomalous results seen in other research on small particles, Li says.

For more details about the various attempts to create smaller computer chips, you can read my July 11, 2014 posting about IBM and its proposed 7 nanometer chip where you will also find links to announcements and posts about Intel’s smaller chips and HP Labs’ attempt to recreate computers.

As for the research into liquid-like metallic (silver) nanoparticles, here’s a link to and a citation for the paper,

Liquid-like pseudoelasticity of sub-10-nm crystalline ​silver particle by Jun Sun, Longbing He, Yu-Chieh Lo, Tao Xu, Hengchang Bi, Litao Sun, Ze Zhang, Scott X. Mao, & Ju Li. Nature Materials (2014) doi:10.1038/nmat4105 Published online 12 October 2014

This paper is behind a paywall. There is a free preview via ReadCube Access.

Nanotechnology for better treatment of eye conditions and a perspective on superhuman sight

There are three ‘eye’-related items in this piece, two of them concerning animal eyes and one concerning a camera-eye or the possibility of superhuman sight.

Earlier this week researchers at the University of Reading (UK) announced they have achieved a better understanding of how nanoparticles might be able to bypass some of the eye’s natural barriers in the hopes of making eye drops more effective in an Oct. 7, 2014 news item on Nanowerk,

Sufferers of eye disorders have new hope after researchers at the University of Reading discovered a potential way of making eye drops more effective.

Typically less than 5% of the medicine dose applied as drops actually penetrates the eye – the majority of the dose will be washed off the cornea by tear fluid and lost.

The team, led by Professor Vitaliy Khutoryanskiy, has developed novel nanoparticles that could attach to the cornea and resist the wash out effect for an extended period of time. If these nanoparticles are loaded with a drug, their longer attachment to the cornea will ensure more medicine penetrates the eye and improves drop treatment.

An Oct. 6, 2014 University of Reading press release, which originated the news item, provides more information about the hoped for impact of this work while providing few details about the research (Note: A link has been removed),

The research could also pave the way for new treatments of currently incurable eye-disorders such as Age-related Macular Degeneration (AMD) – the leading cause of visual impairment with around 500,000 sufferers in the UK.

There is currently no cure for this condition but experts believe the progression of AMD could be slowed considerably using injections of medicines into the eye. However, eye-drops with drug-loaded nanoparticles could be a potentially more effective and desirable course of treatment.

Professor Vitaliy Khutoryanskiy, from the University of Reading’s School of Pharmacy, said: “Treating eye disorders is a challenging task. Our corneas allow us to see and serve as a barrier that protects our eyes from microbial and chemical intervention. Unfortunately this barrier hinders the effectiveness of eye drops. Many medicines administered to the eye are inefficient as they often cannot penetrate the cornea barrier. Only the very small molecules in eye drops can penetrate healthy cornea.

“Many recent breakthroughs to treat eye conditions involve the use of drugs incorporated into nano-containers; their role being to promote drug penetration into the eye.  However the factors affecting this penetration remain poorly understood. Our research also showed that penetration of small drug molecules could be improved by adding enhancers such as cyclodextrins. This means eye drops have the potential to be a more effective, and a more comfortable, future treatment for disorders such as AMD.”

The finding is one of a number of important discoveries highlighted in a paper published today in the journal Molecular Pharmaceutics. The researchers revealed fascinating insights into how the structure of the cornea prevents various small and large molecules, as well as nanoparticles, from entering into the eye. They also examined the effects any damage to the eye would have in allowing these materials to enter the body.

Professor Khutoryanskiy continued: “There is increasing concern about the safety of environmental contaminants, pollutants and nanoparticles and their potential impacts on human health. We tested nanoparticles whose sizes ranged between 21 – 69 nm, similar to the size of viruses such as polio, or similar to airborn particles originating from building industry and found that they could not penetrate healthy and intact cornea irrespective of their chemical nature.

“However if the top layer of the cornea is damaged, either after surgical operation or accidentally, then the eye’s natural defence may be compromised and it becomes susceptible to viral attack which could result in eye infections.

“The results show that our eyes are well-equipped to defend us against potential airborne threats that exist in a fast-developing industrialised world. However we need to be aware of the potential complications that may arise if the cornea is damaged, and not treated quickly and effectively.”

Here’s a link to and a citation for the paper,

On the Barrier Properties of the Cornea: A Microscopy Study of the Penetration of Fluorescently Labeled Nanoparticles, Polymers, and Sodium Fluorescein by Ellina A. Mun, Peter W. J. Morrison, Adrian C. Williams, and Vitaliy V. Khutoryanskiy. Mol. Pharmaceutics, 2014, 11 (10), pp 3556–3564 DOI: 10.1021/mp500332m Publication Date (Web): August 28, 2014

Copyright © 2014 American Chemical Society

There’s a little more information to be had in the paper’s abstract, which is, as these things go, is relatively accessible,

[downloaded from http://pubs.acs.org/doi/abs/10.1021/mp500332m]

[downloaded from http://pubs.acs.org/doi/abs/10.1021/mp500332m]

Overcoming the natural defensive barrier functions of the eye remains one of the greatest challenges of ocular drug delivery. Cornea is a chemical and mechanical barrier preventing the passage of any foreign bodies including drugs into the eye, but the factors limiting penetration of permeants and nanoparticulate drug delivery systems through the cornea are still not fully understood. In this study, we investigate these barrier properties of the cornea using thiolated and PEGylated (750 and 5000 Da) nanoparticles, sodium fluorescein, and two linear polymers (dextran and polyethylene glycol). Experiments used intact bovine cornea in addition to bovine cornea de-epithelialized or tissues pretreated with cyclodextrin. It was shown that corneal epithelium is the major barrier for permeation; pretreatment of the cornea with β-cyclodextrin provides higher permeation of low molecular weight compounds, such as sodium fluorescein, but does not enhance penetration of nanoparticles and larger molecules. Studying penetration of thiolated and PEGylated (750 and 5000 Da) nanoparticles into the de-epithelialized ocular tissue revealed that interactions between corneal surface and thiol groups of nanoparticles were more significant determinants of penetration than particle size (for the sizes used here). PEGylation with polyethylene glycol of a higher molecular weight (5000 Da) allows penetration of nanoparticles into the stroma, which proceeds gradually, after an initial 1 h lag phase.

The paper is behind a paywall. No mention is made in the abstract or in the press release as to how the bovine (ox, cow, or buffalo) eyes were obtained but I gather these body parts are often harvested from animals that have been previously slaughtered for food.

This next item also concerns research about eye drops but this time the work comes from the University of Waterloo (Ontario, Canada). From an Oct. 8, 2014 news item on Azonano,

For the millions of sufferers of dry eye syndrome, their only recourse to easing the painful condition is to use drug-laced eye drops three times a day. Now, researchers from the University of Waterloo have developed a topical solution containing nanoparticles that will combat dry eye syndrome with only one application a week.

An Oct. 8, 2014 University of Waterloo news release (also on EurekAlert), which originated the news item, describes the results of the work without providing much detail about the nanoparticles used to deliver the treatment via eye drops,

The eye drops progressively deliver the right amount of drug-infused nanoparticles to the surface of the eyeball over a period of five days before the body absorbs them.  One weekly dose replaces 15 or more to treat the pain and irritation of dry eyes.

The nanoparticles, about 1/1000th the width of a human hair, stick harmlessly to the eye’s surface and use only five per cent of the drug normally required.

“You can’t tell the difference between these nanoparticle eye drops and water,” said Shengyan (Sandy) Liu, a PhD candidate at Waterloo’s Faculty of Engineering, who led the team of researchers from the Department of Chemical Engineering and the Centre for Contact Lens Research. “There’s no irritation to the eye.”

Dry eye syndrome is a more common ailment for people over the age of 50 and may eventually lead to eye damage. More than six per cent of people in the U.S. have it. Currently, patients must frequently apply the medicine three times a day because of the eye’s ability to self-cleanse—a process that washes away 95 per cent of the drug.

“I knew that if we focused on infusing biocompatible nanoparticles with Cyclosporine A, the drug in the eye drops, and make them stick to the eyeball without irritation for longer periods of time, it would also save patients time and reduce the possibility of toxic exposure due to excessive use of eye drops,” said Liu.

The research team is now focusing on preparing the nanoparticle eye drops for clinical trials with the hope that this nanoparticle therapy could reach the shelves of drugstores within five years.

Here’s a link to and a citation for the paper,

Phenylboronic acid modified mucoadhesive nanoparticle drug carriers facilitate weekly treatment of experimentallyinduced dry eye syndrome by Shengyan Liu, Chu Ning Chang, Mohit S. Verma, Denise Hileeto, Alex Muntz, Ulrike Stahl, Jill Woods, Lyndon W. Jones, and Frank X. Gu. Nano Research (October 2014) DOI: 10.1007/s12274-014-0547-3

This paper is behind a paywall. There is a partial preview available for free. As per the paper’s abstract, research was performed on healthy rabbit eyes.

The last ‘sight’ item I’m featuring here comes from the Massachusetts Institute of Technology (MIT) and does not appear to have been occasioned by the publication of a research paper or some other event. From an Oct. 7, 2014 news item on Azonano,

All through his childhood, Ramesh Raskar wished fervently for eyes in the back of his head. “I had the notion that the world did not exist if I wasn’t looking at it, so I would constantly turn around to see if it was there behind me.” Although this head-spinning habit faded during his teen years, Raskar never lost the desire to possess the widest possible field of vision.

Today, as director of the Camera Culture research group and associate professor of Media Arts and Sciences at the MIT Media Lab, Raskar is realizing his childhood fantasy, and then some. His inventions include a nanocamera that operates at the speed of light and do-it-yourself tools for medical imaging. His scientific mission? “I want to create not just a new kind of vision, but superhuman vision,” Raskar says.

An Oct. 6, 2014 MIT news release, which originated the news item, provides more information about Raskar and his research,

He avoids research projects launched with a goal in mind, “because then you only come up with the same solutions as everyone else.” Discoveries tend to cascade from one area into another. For instance, Raskar’s novel computational methods for reducing motion blur in photography suggested new techniques for analyzing how light propagates. “We do matchmaking; what we do here can be used over there,” says Raskar.

Inspired by the famous microflash photograph of a bullet piercing an apple, created in 1964 by MIT professor and inventor Harold “Doc” Edgerton, Raskar realized, “I can do Edgerton millions of times faster.” This led to one of the Camera Culture group’s breakthrough inventions, femtophotography, a process for recording light in flight.

Manipulating photons into a packet resembling Edgerton’s bullet, Raskar and his team were able to “shoot” ultrashort laser pulses through a Coke bottle. Using a special camera to capture the action of these pulses at half a trillion frames per second with two-trillionths of a second exposure times, they captured moving images of light, complete with wave-like shadows lapping at the exterior of the bottle.

Femtophotography opened up additional avenues of inquiry, as Raskar pondered what other features of the world superfast imaging processes might reveal. He was particularly intrigued by scattered light, the kind in evidence when fog creates the visual equivalent of “noise.”

In one experiment, Raskar’s team concealed an object behind a wall, out of camera view. By firing super-short laser bursts onto a surface nearby, and taking millions of exposures of light bouncing like a pinball around the scene, the group rendered a picture of the hidden object. They had effectively created a camera that peers around corners, an invention that might someday help emergency responders safely investigate a dangerous environment.

Raskar’s objective of “making the invisible visible” extends as well to the human body. The Camera Culture group has developed a technique for taking pictures of the eye using cellphone attachments, spawning inexpensive, patient-managed vision and disease diagnostics. Conventional photography has evolved from time-consuming film development to instantaneous digital snaps, and Raskar believes “the same thing will happen to medical imaging.” His research group intends “to break all the rules and be at the forefront. I think we’ll get there in the next few years,” he says.

Ultimately, Raskar predicts, imaging will serve as a catalyst of transformation in all dimensions of human life — change that can’t come soon enough for him. “I hate ordinary cameras,” he says. “They record only what I see. I want a camera that gives me a superhuman perspective.”

Following the link to the MIT news release will lead you to more information about Raskar and his work. You can also see and hear Raskar talk about his femtophotography in a 2012 TEDGlobal talk here.