Tag Archives: 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.

Next supercapacitor: crumpled graphene?

An Oct. 3, 2014 news item on ScienceDaily features the use of graphene as a possible supercapacitor,

When someone crumples a sheet of paper, that usually means it’s about to be thrown away. But researchers have now found that crumpling a piece of graphene “paper” — a material formed by bonding together layers of the two-dimensional form of carbon — can actually yield new properties that could be useful for creating extremely stretchable supercapacitors to store energy for flexible electronic devices.

The finding is reported in the journal Scientific Reports by MIT’s {Massachusetts Institute of Technology] Xuanhe Zhao, an assistant professor of mechanical engineering and civil and environmental engineering, and four other authors. The new, flexible superconductors should be easy and inexpensive to fabricate, the team says.

An Oct. 3, 2014 MIT news release by David Chandler (also on EurekAlert), which originated the news item, explains the technology at more length,

“Many people are exploring graphene paper: It’s a good candidate for making supercapacitors, because of its large surface area per mass,” Zhao says. Now, he says, the development of flexible electronic devices, such as wearable or implantable biomedical sensors or monitoring devices, will require flexible power-storage systems.

Like batteries, supercapacitors can store electrical energy, but they primarily do so electrostatically, rather than chemically — meaning they can deliver their energy faster than batteries can. Now Zhao and his team have demonstrated that by crumpling a sheet of graphene paper into a chaotic mass of folds, they can make a supercapacitor that can easily be bent, folded, or stretched to as much as 800 percent of its original size. The team has made a simple supercapacitor using this method as a proof of principle.

The material can be crumpled and flattened up to 1,000 times, the team has demonstrated, without a significant loss of performance. “The graphene paper is pretty robust,” Zhao says, “and we can achieve very large deformations over multiple cycles.” Graphene, a structure of pure carbon just one atom thick with its carbon atoms arranged in a hexagonal array, is one of the strongest materials known.

To make the crumpled graphene paper, a sheet of the material was placed in a mechanical device that first compressed it in one direction, creating a series of parallel folds or pleats, and then in the other direction, leading to a chaotic, rumpled surface. When stretched, the material’s folds simply smooth themselves out.

Forming a capacitor requires two conductive layers — in this case, two sheets of crumpled graphene paper — with an insulating layer in between, which in this demonstration was made from a hydrogel material. Like the crumpled graphene, the hydrogel is highly deformable and stretchable, so the three layers remain in contact even while being flexed and pulled.

Though this initial demonstration was specifically to make a supercapacitor, the same crumpling technique could be applied to other uses, Zhao says. For example, the crumpled graphene material might be used as one electrode in a flexible battery, or could be used to make a stretchable sensor for specific chemical or biological molecules.

Here is a link to and a citation for the paper,

Stretchable and High-Performance Supercapacitors with Crumpled Graphene Papers by Jianfeng Zang, Changyong Cao, Yaying Feng, Jie Liu, & Xuanhe Zhao. Scientific Reports 4, Article number: 6492 doi:10.1038/srep06492 Published 01 October 2014

This is an open access article.

ETA Oct. 8, 2014: Dexter Johnson of the Nanoclast blog on the IEEE (Institute of Electrical and Electronics Engineers) website has an Oct. 7, 2014 post where he comments about the ‘flexibility’ aspect of this work.

Things falling apart: both a Nigerian novel and research at the Massachusetts Intitute of Technology

First the Nigerian novel ‘Things Fall Apart‘ (from its Wikipedia entry; Note: Links have been removed),

Things Fall Apart is an English-language novel by Nigerian author Chinua Achebe published in 1958 by William Heinemann Ltd in the UK; in 1962, it was also the first work published in Heinemann’s African Writers Series. Things Fall Apart is seen as the archetypal modern African novel in English, one of the first to receive global critical acclaim. It is a staple book in schools throughout Africa and is widely read and studied in English-speaking countries around the world. The title of the novel comes from William Butler Yeats’ poem “The Second Coming”.[1]

For those unfamiliar with the Yeats poem, this is the relevant passage (from Wikipedia entry for The Second Coming),

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.

The other ‘Things fall apart’ item, although it’s an investigation into ‘how things fall apart’, is mentioned in an Aug. 4, 2014 news item on Nanowerk,

Materials that are firmly bonded together with epoxy and other tough adhesives are ubiquitous in modern life — from crowns on teeth to modern composites used in construction. Yet it has proved remarkably difficult to study how these bonds fracture and fail, and how to make them more resistant to such failures.

Now researchers at MIT [Massachusetts Institute of Technology] have found a way to study these bonding failures directly, revealing the crucial role of moisture in setting the stage for failure. Their findings are published in the journal Proceedings of the National Academy of Science in a paper by MIT professors of civil and environmental engineering Oral Buyukozturk and Markus Buehler; research associate Kurt Broderick of MIT’s Microsystems Technology Laboratories; and doctoral student Denvid Lau, who has since joined the faculty at the City University of Hong Kong.

An Aug. 4, 2014 MIT news release written by David Chandler (also on EurekAlert), which originated the news item, provides an unexpectedly fascinating discussion of bonding, interfaces, and infrastructure,

“The bonding problem is a general problem that is encountered in many disciplines, especially in medicine and dentistry,” says Buyukozturk, whose research has focused on infrastructure, where such problems are also of great importance. “The interface between a base material and epoxy, for example, really controls the properties. If the interface is weak, you lose the entire system.”

“The composite may be made of a strong and durable material bonded to another strong and durable material,” Buyukozturk adds, “but where you bond them doesn’t necessarily have to be strong and durable.”

Besides dental implants and joint replacements, such bonding is also critical in construction materials such as fiber-reinforced polymers and reinforced concrete. But while such materials are widespread, understanding how they fail is not simple.

There are standard methods for testing the strength of materials and how they may fail structurally, but bonded surfaces are more difficult to model. “When we are concerned with deterioration of this interface when it is degraded by moisture, classical methods can’t handle that,” Buyukozturk says. “The way to approach it is to look at the molecular level.”

When such systems are exposed to moisture, “it initiates new molecules at the interface,” Buyukozturk says, “and that interferes with the bonding mechanism. How do you assess how weak the interface becomes when it is affected? We came up with an innovative method to assess the interface weakening as a result of exposure to environmental effects.”

The team used a combination of molecular simulations and laboratory tests in its assessment. The modeling was based on fundamental principles of molecular interactions, not on empirical data, Buyukozturk says.

In the laboratory tests, Buyukozturk and his colleagues controlled the residual stresses in a metal layer that was bonded and then forcibly removed. “We validated the method, and showed that moisture has a degrading effect,” he says.

The findings could lead to exploration of new ways to prevent moisture from reaching into the bonded layer, perhaps using better sealants. “Moisture is the No. 1 enemy,” Buyukozturk says.

“I think this is going to be an important step toward assessment of the bonding, and enable us to design more durable composites,” he adds. “It gives a quantitative knowledge of the interface” — for example, predicting that under specific conditions, a given bonded material will lose 30 percent of its strength.

Interface problems are universal, Buyukozturk says, occurring in many areas besides biomedicine and construction. “They occur in mechanical devices, in aircraft, electrical equipment, in the packaging of electronic components,” he says. “We feel this will have very broad applications.”

Bonded composite materials are beginning to be widely used in airplane manufacturing; often these composites are then bonded to traditional materials, like aluminum. “We have not had enough experience to prove the durability of these composite systems is going to be there after 20 years,” Buyukozturk says.

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

A robust nanoscale experimental quantification of fracture energy in a bilayer material system by Denvid Lau, Kurt Broderick, Markus J. Buehler, and Oral Büyüköztürk. PNAS, doi: 10.1073/pnas.1402893111 published August 5, 2014

This paper is behind a paywall.

Gold on the brain, a possible nanoparticle delivery system for drugs

A July 21, 2014 news item on Nanowerk describes special gold nanoparticles that could make drug delivery to cells easier,

A special class of tiny gold particles can easily slip through cell membranes, making them good candidates to deliver drugs directly to target cells.

A new study from MIT materials scientists reveals that these nanoparticles enter cells by taking advantage of a route normally used in vesicle-vesicle fusion, a crucial process that allows signal transmission between neurons.

A July 21, 2014 MIT (Massachusetts Institute of Technology) news release (also on EurekAlert), which originated the news item, provides more details,

The findings suggest possible strategies for designing nanoparticles — made from gold or other materials — that could get into cells even more easily.

“We’ve identified a type of mechanism that might be more prevalent than is currently known,” says Reid Van Lehn, an MIT graduate student in materials science and engineering and one of the paper’s lead authors. “By identifying this pathway for the first time it also suggests not only how to engineer this particular class of nanoparticles, but that this pathway might be active in other systems as well.”

The paper’s other lead author is Maria Ricci of École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. The research team, led by Alfredo Alexander-Katz, an associate professor of materials science and engineering, and Francesco Stellacci from EPFL, also included scientists from the Carlos Besta Institute of Neurology in Italy and Durham University in the United Kingdom.

Most nanoparticles enter cells through endocytosis, a process that traps the particles in intracellular compartments, which can damage the cell membrane and cause cell contents to leak out. However, in 2008, Stellacci, who was then at MIT, and Darrell Irvine, a professor of materials science and engineering and of biological engineering, found that a special class of gold nanoparticles coated with a mix of molecules could enter cells without any disruption.

“Why this was happening, or how this was happening, was a complete mystery,” Van Lehn says.

Last year, Alexander-Katz, Van Lehn, Stellacci, and others discovered that the particles were somehow fusing with cell membranes and being absorbed into the cells. In their new study, they created detailed atomistic simulations to model how this happens, and performed experiments that confirmed the model’s predictions.

Gold nanoparticles used for drug delivery are usually coated with a thin layer of molecules that help tune their chemical properties. Some of these molecules, or ligands, are negatively charged and hydrophilic, while the rest are hydrophobic. The researchers found that the particles’ ability to enter cells depends on interactions between hydrophobic ligands and lipids found in the cell membrane.

Cell membranes consist of a double layer of phospholipid molecules, which have hydrophobic lipid tails and hydrophilic heads. The lipid tails face in toward each other, while the hydrophilic heads face out.

In their computer simulations, the researchers first created what they call a “perfect bilayer,” in which all of the lipid tails stay in place within the membrane. Under these conditions, the researchers found that the gold nanoparticles could not fuse with the cell membrane.

However, if the model membrane includes a “defect” — an opening through which lipid tails can slip out — nanoparticles begin to enter the membrane. When these lipid protrusions occur, the lipids and particles cling to each other because they are both hydrophobic, and the particles are engulfed by the membrane without damaging it.

In real cell membranes, these protrusions occur randomly, especially near sites where proteins are embedded in the membrane. They also occur more often in curved sections of membrane, because it’s harder for the hydrophilic heads to fully cover a curved area than a flat one, leaving gaps for the lipid tails to protrude.

“It’s a packing problem,” Alexander-Katz says. “There’s open space where tails can come out, and there will be water contact. It just makes it 100 times more probable to have one of these protrusions come out in highly curved regions of the membrane.”

This phenomenon appears to mimic a process that occurs naturally in cells — the fusion of vesicles with the cell membrane. Vesicles are small spheres of membrane-like material that carry cargo such as neurotransmitters or hormones.

The similarity between absorption of vesicles and nanoparticle entry suggests that cells where a lot of vesicle fusion naturally occurs could be good targets for drug delivery by gold nanoparticles. The researchers plan to further analyze how the composition of the membranes and the proteins embedded in them influence the absorption process in different cell types. “We want to really understand all the constraints and determine how we can best design nanoparticles to target particular cell types, or regions of a cell,” Van Lehn says.

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

Lipid tail protrusions mediate the insertion of nanoparticles into model cell membranes by Reid C. Van Lehn, Maria Ricci, Paulo H.J. Silva, Patrizia Andreozzi, Javier Reguera, Kislon Voïtchovsky, Francesco Stellacci, & Alfredo Alexander-Katz. Nature Communications 5, Article number: 4482 doi:10.1038/ncomms5482 Published 21 July 2014

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

I last featured this multi-country team’s work on gold nanoparticles in an Aug. 23, 2013 posting.

Steampower via nanotechnology

It seems that researchers at MIT (Massachusetts Institute of Technology (US) have been inspired by steam punk, of a sort. From a July 21, 2014 news item on Nanowerk,

A new material structure developed at MIT generates steam by soaking up the sun.

The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.

The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation. What’s more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.

A July 21, 2014 MIT news release, which originated the news item, details the research,

Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials — a particular advantage for a variety of compact, steam-powered applications.

“Steam is important for desalination, hygiene systems, and sterilization,” says Ghasemi, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”

Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.

Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy — about 1,000 times that of an average sunny day.

By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day — the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.

“This is a huge advantage in cost-reduction,” Ghasemi says. “That’s exciting for us because we’ve come up with a new approach to solar steam generation.”

The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid’s surface.

After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is “just like popcorn”: The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.

The structure’s bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.

As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.

The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator — a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.

Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.

“There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations,” Ghasemi says. “There is still a lot of research that can be done on implementing this in larger systems.”

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

Solar steam generation by heat localization by Hadi Ghasemi, George Ni, Amy Marie Marconnet, James Loomis, Selcuk Yerci, Nenad Miljkovic, & Gang Chen. Nature Communications 5, Article number: 4449 doi:10.1038/ncomms5449 Published 21 July 2014

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

Squishy but rigid robots from MIT (Massachusetts Institute of Technology)

A July 14, 2014 news item on ScienceDaily MIT (Massachusetts Institute of Technology) features robots that mimic mice and other biological constructs or, if you prefer, movie robots,

In the movie “Terminator 2,” the shape-shifting T-1000 robot morphs into a liquid state to squeeze through tight spaces or to repair itself when harmed.

Now a phase-changing material built from wax and foam, and capable of switching between hard and soft states, could allow even low-cost robots to perform the same feat.

The material — developed by Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, and her former graduate student Nadia Cheng, alongside researchers at the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University — could be used to build deformable surgical robots. The robots could move through the body to reach a particular point without damaging any of the organs or vessels along the way.

A July 14, 2014 MIT news release (also on EurekAlert), which originated the news item, describes the research further by referencing both octopuses and jello,

Working with robotics company Boston Dynamics, based in Waltham, Mass., the researchers began developing the material as part of the Chemical Robots program of the Defense Advanced Research Projects Agency (DARPA). The agency was interested in “squishy” robots capable of squeezing through tight spaces and then expanding again to move around a given area, Hosoi says — much as octopuses do.

But if a robot is going to perform meaningful tasks, it needs to be able to exert a reasonable amount of force on its surroundings, she says. “You can’t just create a bowl of Jell-O, because if the Jell-O has to manipulate an object, it would simply deform without applying significant pressure to the thing it was trying to move.”

What’s more, controlling a very soft structure is extremely difficult: It is much harder to predict how the material will move, and what shapes it will form, than it is with a rigid robot.

So the researchers decided that the only way to build a deformable robot would be to develop a material that can switch between a soft and hard state, Hosoi says. “If you’re trying to squeeze under a door, for example, you should opt for a soft state, but if you want to pick up a hammer or open a window, you need at least part of the machine to be rigid,” she says.

Compressible and self-healing

To build a material capable of shifting between squishy and rigid states, the researchers coated a foam structure in wax. They chose foam because it can be squeezed into a small fraction of its normal size, but once released will bounce back to its original shape.

The wax coating, meanwhile, can change from a hard outer shell to a soft, pliable surface with moderate heating. This could be done by running a wire along each of the coated foam struts and then applying a current to heat up and melt the surrounding wax. Turning off the current again would allow the material to cool down and return to its rigid state.

In addition to switching the material to its soft state, heating the wax in this way would also repair any damage sustained, Hosoi says. “This material is self-healing,” she says. “So if you push it too far and fracture the coating, you can heat it and then cool it, and the structure returns to its original configuration.”

To build the material, the researchers simply placed the polyurethane foam in a bath of melted wax. They then squeezed the foam to encourage it to soak up the wax, Cheng says. “A lot of materials innovation can be very expensive, but in this case you could just buy really low-cost polyurethane foam and some wax from a craft store,” she says.

In order to study the properties of the material in more detail, they then used a 3-D printer to build a second version of the foam lattice structure, to allow them to carefully control the position of each of the struts and pores.

When they tested the two materials, they found that the printed lattice was more amenable to analysis than the polyurethane foam, although the latter would still be fine for low-cost applications, Hosoi says.

The wax coating could also be replaced by a stronger material, such as solder, she adds.

Hosoi is now investigating the use of other unconventional materials for robotics, such as magnetorheological and electrorheological fluids. These materials consist of a liquid with particles suspended inside, and can be made to switch from a soft to a rigid state with the application of a magnetic or electric field.

When it comes to artificial muscles for soft and biologically inspired robots, we tend to think of controlling shape through bending or contraction, says Carmel Majidi, an assistant professor of mechanical engineering in the Robotics Institute at Carnegie Mellon University, who was not involved in the research. “But for a lot of robotics tasks, reversibly tuning the mechanical rigidity of a joint can be just as important,” he says. “This work is a great demonstration of how thermally controlled rigidity-tuning could potentially be used in soft robotics.”

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

Thermally Tunable, Self-Healing Composites for Soft Robotic Applications by Nadia G. Cheng, Arvind Gopinath, Lifeng Wang, Karl Iagnemma, and Anette E. Hosoi. Macromolecular Materials and Engineering DOI: 10.1002/mame.201400017 Article first published online: 30 JUN 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.