Tag Archives: Harvard University

SINGLE (3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy) and the 3D structures of two individual platinum nanoparticles in solution

It seems to me there’s been an explosion of new imaging techniques lately. This one from the Lawrence Berkelely National Laboratory is all about imaging colloidal nanoparticles (nanoparticles in solution), from a July 20, 2015 news item on Azonano,

Just as proteins are one of the basic building blocks of biology, nanoparticles can serve as the basic building blocks for next generation materials. In keeping with this parallel between biology and nanotechnology, a proven technique for determining the three dimensional structures of individual proteins has been adapted to determine the 3D structures of individual nanoparticles in solution.

A multi-institutional team of researchers led by the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), has developed a new technique called “SINGLE” that provides the first atomic-scale images of colloidal nanoparticles. SINGLE, which stands for 3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy, has been used to separately reconstruct the 3D structures of two individual platinum nanoparticles in solution.

A July 16, 2015 Berkeley Lab news release, which originated the news item, reveals more details about the reason for the research and the research itself,

“Understanding structural details of colloidal nanoparticles is required to bridge our knowledge about their synthesis, growth mechanisms, and physical properties to facilitate their application to renewable energy, catalysis and a great many other fields,” says Berkeley Lab director and renowned nanoscience authority Paul Alivisatos, who led this research. “Whereas most structural studies of colloidal nanoparticles are performed in a vacuum after crystal growth is complete, our SINGLE method allows us to determine their 3D structure in a solution, an important step to improving the design of nanoparticles for catalysis and energy research applications.”

Alivisatos, who also holds the Samsung Distinguished Chair in Nanoscience and Nanotechnology at the University of California Berkeley, and directs the Kavli Energy NanoScience Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper detailing this research in the journal Science. The paper is titled “3D Structure of Individual Nanocrystals in Solution by Electron Microscopy.” The lead co-authors are Jungwon Park of Harvard University, Hans Elmlund of Australia’s Monash University, and Peter Ercius of Berkeley Lab. Other co-authors are Jong Min Yuk, David Limmer, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David Weitz and Alex Zettl.

Colloidal nanoparticles are clusters of hundreds to thousands of atoms suspended in a solution whose collective chemical and physical properties are determined by the size and shape of the individual nanoparticles. Imaging techniques that are routinely used to analyze the 3D structure of individual crystals in a material can’t be applied to suspended nanomaterials because individual particles in a solution are not static. The functionality of proteins are also determined by their size and shape, and scientists who wanted to image 3D protein structures faced a similar problem. The protein imaging problem was solved by a technique called “single-particle cryo-electron microscopy,” in which tens of thousands of 2D transmission electron microscope (TEM) images of identical copies of an individual protein or protein complex frozen in random orientations are recorded then computationally combined into high-resolution 3D reconstructions. Alivisatos and his colleagues utilized this concept to create their SINGLE technique.

“In materials science, we cannot assume the nanoparticles in a solution are all identical so we needed to develop a hybrid approach for reconstructing the 3D structures of individual nanoparticles,” says co-lead author of the Science paper Peter Ercius, a staff scientist with the National Center for Electron Microscopy (NCEM) at the Molecular Foundry, a DOE Office of Science User Facility.

“SINGLE represents a combination of three technological advancements from TEM imaging in biological and materials science,” Ercius says. “These three advancements are the development of a graphene liquid cell that allows TEM imaging of nanoparticles rotating freely in solution, direct electron detectors that can produce movies with millisecond frame-to-frame time resolution of the rotating nanocrystals, and a theory for ab initio single particle 3D reconstruction.”

The graphene liquid cell (GLC) that helped make this study possible was also developed at Berkeley Lab under the leadership of Alivisatos and co-author Zettl, a physicist who also holds joint appointments with Berkeley Lab, UC Berkeley and Kavli ENSI. TEM imaging uses a beam of electrons rather than light for illumination and magnification but can only be used in a high vacuum because molecules in the air disrupt the electron beam. Since liquids evaporate in high vacuum, samples in solutions must be hermetically sealed in special solid containers – called cells – with a very thin viewing window before being imaged with TEM. In the past, liquid cells featured silicon-based viewing windows whose thickness limited resolution and perturbed the natural state of the sample materials. The GLC developed at Berkeley lab features a viewing window made from a graphene sheet that is only a single atom thick.

“The GLC provides us with an ultra-thin covering of our nanoparticles while maintaining liquid conditions in the TEM vacuum,” Ercius says. “Since the graphene surface of the GLC is inert, it does not adsorb or otherwise perturb the natural state of our nanoparticles.”

Working at NCEM’s TEAM I, the world’s most powerful electron microscope, Ercius, Alivisatos and their colleagues were able to image in situ the translational and rotational motions of individual nanoparticles of platinum that were less than two nanometers in diameter. Platinum nanoparticles were chosen because of their high electron scattering strength and because their detailed atomic structure is important for catalysis.

“Our earlier GLC studies of platinum nanocrystals showed that they grow by aggregation, resulting in complex structures that are not possible to determine by any previously developed method,” Ercius says. “Since SINGLE derives its 3D structures from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.”

The next step for SINGLE is to recover a full 3D atomic resolution density map of colloidal nanoparticles using a more advanced camera installed on TEAM I that can provide 400 frames-per-second and better image quality.

“We plan to image defects in nanoparticles made from different materials, core shell particles, and also alloys made of two different atomic species,” Ercius says. [emphasis mine]

“Two different atomic species?”, they really are pushing that biology analogy.

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

3D structure of individual nanocrystals in solution by electron microscopy by Jungwon Park, Hans Elmlund, Peter Ercius, Jong Min Yuk, David T. Limme, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David A. Weitz, A. Zettl, A. Paul Alivisatos. Science 17 July 2015: Vol. 349 no. 6245 pp. 290-295 DOI: 10.1126/science.aab1343

This paper is behind a paywall.

Injectable electronics

Having taught a course on bioelectronics for Simon Fraser University’s (Vancouver, Canada) Continuing Studies Program, this  latest work from Harvard University (US) caught my attention. A Harvard research team has developed a technique which could allow doctors to inject us with electronics, should we need them. From a June 8, 2015 news item on phys.org,

It’s a notion that might be pulled from the pages of science-fiction novel – electronic devices that can be injected directly into the brain, or other body parts, and treat everything from neurodegenerative disorders to paralysis.

It sounds unlikely, until you visit Charles Lieber’s lab.

A team of international researchers, led by Lieber, the Mark Hyman, Jr. Professor of Chemistry, an international team of researchers developed a method for fabricating nano-scale electronic scaffolds that can be injected via syringe. Once connected to electronic devices, the scaffolds can be used to monitor neural activity, stimulate tissues and even promote regenerations of neurons. …

Here’s an image provided by the researchers,

Bright-field image showing the mesh electronics being injected through sub-100 micrometer inner diameter glass needle into aqueous solution. mage courtesy of Lieber Research Group, Harvard University

Bright-field image showing the mesh electronics being injected through sub-100 micrometer inner diameter glass needle into aqueous solution. mage courtesy of Lieber Research Group, Harvard University

A June 8, 2015 Harvard University new release by Peter Reuell (also on EurekAlert), which originated the news item, describes the work in more detail,

“I do feel that this has the potential to be revolutionary,” Lieber said. “This opens up a completely new frontier where we can explore the interface between electronic structures and biology. For the past thirty years, people have made incremental improvements in micro-fabrication techniques that have allowed us to make rigid probes smaller and smaller, but no one has addressed this issue – the electronics/cellular interface – at the level at which biology works.”

The idea of merging the biological with the electronic is not a new one for Lieber.

In an earlier study, scientists in Lieber’s lab demonstrated that the scaffolds could be used to create “cyborg” tissue – when cardiac or nerve cells were grown with embedded scaffolds. [emphasis mine] Researchers were then able to use the devices to record electrical signals generated by the tissues, and to measure changes in those signals as they administered cardio- or neuro-stimulating drugs.

“We were able to demonstrate that we could make this scaffold and culture cells within it, but we didn’t really have an idea how to insert that into pre-existing tissue,” Lieber said. “But if you want to study the brain or develop the tools to explore the brain-machine interface, you need to stick something into the body. When releasing the electronics scaffold completely from the fabrication substrate, we noticed that it was almost invisible and very flexible like a polymer and could literally be sucked into a glass needle or pipette. From there, we simply asked, would it be possible to deliver the mesh electronics by syringe needle injection, a process common to delivery of many species in biology and medicine – you could go to the doctor and you inject this and you’re wired up.'”

Though not the first attempts at implanting electronics into the brain – deep brain stimulation has been used to treat a variety of disorders for decades – the nano-fabricated scaffolds operate on a completely different scale.

“Existing techniques are crude relative to the way the brain is wired,” Lieber explained. “Whether it’s a silicon probe or flexible polymers…they cause inflammation in the tissue that requires periodically changing the position or the stimulation. But with our injectable electronics, it’s as if it’s not there at all. They are one million times more flexible than any state-of-the-art flexible electronics and have subcellular feature sizes. They’re what I call “neuro-philic” – they actually like to interact with neurons..”

Despite their enormous potential, the fabrication of the injectable scaffolds is surprisingly easy.

“That’s the beauty of this – it’s compatible with conventional manufacturing techniques,” Lieber said.

The process is similar to that used to etch microchips, and begins with a dissolvable layer deposited on a substrate. To create the scaffold, researchers lay out a mesh of nanowires sandwiched in layers of organic polymer. The first layer is then dissolved, leaving the flexible mesh, which can be drawn into a syringe needle and administered like any other injection.

After injection, the input/output of the mesh can be connected to standard measurement electronics so that the integrated devices can be addressed and used to stimulate or record neural activity.

“These type of things have never been done before, from both a fundamental neuroscience and medical perspective,” Lieber said. “It’s really exciting – there are a lot of potential applications.”

Going forward, Lieber said, researchers hope to better understand how the brain and other tissues react to the injectable electronics over longer periods.

Lieber’s earlier work on “cyborg tissue” was briefly mentioned here in a Feb. 20, 2014 posting.

Getting back to the most recent work, here’s a link to and a citation for the paper,

Syringe-injectable electronics by Jia Liu, Tian-Ming Fu, Zengguang Cheng, Guosong Hong, Tao Zhou, Lihua Jin, Madhavi Duvvuri, Zhe Jiang, Peter Kruskal, Chong Xie, Zhigang Suo, Ying Fang, & Charles M. Lieber. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.115 Published online 08 June 2015

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

One final note, the researchers have tested the injectable electronics (or mesh electronics) in vivo (live animals).

Animal-based (some of it ‘fishy’) sunscreen from Oregon State University

In the Northern Hemisphere countries it’s time to consider one’s sunscreen options.While this Oregon State University into animal-based sunscreens is intriguing,  market-ready options likely won’t be available for quite some time. (There is a second piece of related research, more ‘fishy’ in nature [pun], featured later in this post.) From a May 12, 2015 Oregon State University news release,

Researchers have discovered why many animal species can spend their whole lives outdoors with no apparent concern about high levels of solar exposure: they make their own sunscreen.

The findings, published today in the journal eLife by scientists from Oregon State University, found that many fish, amphibians, reptiles, and birds can naturally produce a compound called gadusol, which among other biologic activities provides protection from the ultraviolet, or sun-burning component of sunlight.

The researchers also believe that this ability may have been obtained through some prehistoric, natural genetic engineering.

Here’s an amusing image to illustrate the researchers’ point,

Gadusol is the gene found in some animals which gives natural sun protection. Courtesy: Oregon State University

Gadusol is the gene found in some animals which gives natural sun protection.
Courtesy: Oregon State University

The news release goes on to describe gadusol and its believed evolutionary pathway,

The gene that provides the capability to produce gadusol is remarkably similar to one found in algae, which may have transferred it to vertebrate animals – and because it’s so valuable, it’s been retained and passed along for hundreds of millions of years of animal evolution.

“Humans and mammals don’t have the ability to make this compound, but we’ve found that many other animal species do,” said Taifo Mahmud, a professor in the OSU College of Pharmacy, and lead author on the research.

The genetic pathway that allows gadusol production is found in animals ranging from rainbow trout to the American alligator, green sea turtle and a farmyard chicken.

“The ability to make gadusol, which was first discovered in fish eggs, clearly has some evolutionary value to be found in so many species,” Mahmud said. “We know it provides UV-B protection, it makes a pretty good sunscreen. But there may also be roles it plays as an antioxidant, in stress response, embryonic development and other functions.”

In their study, the OSU researchers also found a way to naturally produce gadusol in high volumes using yeast. With continued research, it may be possible to develop gadusol as an ingredient for different types of sunscreen products, cosmetics or pharmaceutical products for humans.

A conceptual possibility, Mahmud said, is that ingestion of gadusol could provide humans a systemic sunscreen, as opposed to a cream or compound that has to be rubbed onto the skin.

The existence of gadusol had been known of in some bacteria, algae and other life forms, but it was believed that vertebrate animals could only obtain it from their diet. The ability to directly synthesize what is essentially a sunscreen may play an important role in animal evolution, and more work is needed to understand the importance of this compound in animal physiology and ecology, the researchers said.

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

De novo synthesis of a sunscreen compound in vertebrates by Andrew R Osborn, Khaled H Almabruk, Garrett Holzwarth, Shumpei Asamizu, Jane LaDu, Kelsey M Kean, P Andrew Karplus, Robert L Tanguay, Alan T Bakalinsky, and Taifo Mahmud. eLife 2015;4:e05919 DOI: http://dx.doi.org/10.7554/eLife.05919 Published May 12, 2015

This is an open access paper.

The second piece of related research, also published yesterday on May 12, 2015, comes from a pair of scientists at Harvard University. From a May 12, 2015  eLife news release on EurekAlert,

Scientists from Oregon State University [two authors are listed for the ‘zebrafish’ paper and both are from Harvard University] have discovered that fish can produce their own sunscreen. They have copied the method used by fish for potential use in humans.

In the study published in the journal eLife, scientists found that zebrafish are able to produce a chemical called gadusol that protects against UV radiation. They successfully reproduced the method that zebrafish use by expressing the relevant genes in yeast. The findings open the door to large-scale production of gadusol for sunscreen and as an antioxidant in pharmaceuticals.

Gadusol was originally identified in cod roe and has since been discovered in the eyes of the mantis shrimp, sea urchin eggs, sponges, and in the dormant eggs and newly hatched larvae of brine shrimps. It was previously thought that fish can only acquire the chemical through their diet or through a symbiotic relationship with bacteria.

Marine organisms in the upper ocean and on reefs are subject to intense and often unrelenting sunlight. Gadusol and related compounds are of great scientific interest for their ability to protect against DNA damage from UV rays. There is evidence that amphibians, reptiles, and birds can also produce gadusol, while the genetic machinery is lacking in humans and other mammals.

The team were investigating compounds similar to gadusol that are used to treat diabetes and fungal infections. It was believed that the biosynthetic enzyme common to all of them, EEVS, was only present in bacteria. The scientists were surprised to discover that fish and other vertebrates contain similar genes to those that code for EEVS.

Curious about their function in animals, they expressed the zebrafish gene in E. coli and analysis suggested that fish combine EEVS with another protein, whose production may be induced by light, to produce gadusol. To check that this combination is really sufficient, the scientists transferred the genes to yeast and set them to work to see what they would create. This confirmed the production of gadusol. Its successful production in yeast provides a viable route to commercialisation.

As well as providing UV protection, gadusol may also play a role in stress responses, in embryonic development, and as an antioxidant.

Here’s a link to and a citation for the second paper from this loosely affiliated team of Oregon State University and Harvard University researchers,

Biochemistry: Shedding light on sunscreen biosynthesis in zebrafish by Carolyn A Brotherton and Emily P Balskus. eLife 2015;4:e07961 DOI: http://dx.doi.org/10.7554/eLife.07961 Published May 12, 2015

This paper, too, is open access.

One final bit and this is about the journal, eLife, from their news release on EurekAlert,

About eLife

eLife is a unique collaboration between the funders and practitioners of research to improve the way important research is selected, presented, and shared. eLife publishes outstanding works across the life sciences and biomedicine — from basic biological research to applied, translational, and clinical studies. eLife is supported by the Howard Hughes Medical Institute, the Max Planck Society, and the Wellcome Trust. Learn more at elifesciences.org.

It seems this journal is a joint, US (Howard Hughes Medical Institute), German (Max Planck Society), UK (Wellcome Trust) effort.

Disinfectants without chemicals for the food industry

Michael Berger in his March 16, 2015 Nanowerk Spotlight article profiles some very interesting research into replacing chemicals with water nanostructures,

The burden of foodborne diseases worldwide is huge, with serious economic and public health consequences. The CDC [US Centers for Disease Control] estimates that each year in the USA approximately 48 million people get sick, 128,000 get hospitalized and 3,000 die from the consumption of food contaminated with pathogenic microorganisms. The food industry is in search of effective intervention methods that can be applied from ‘farm to fork’ to ensure the safety of the food chain and be consumer and environment friendly at the same time.

In the food industry, chemicals are routinely used to clean and disinfect product contact surfaces as well as the outer surface of the food itself. These chemicals provide a necessary and required step to ensure that the foods produced and consumed are as free as possible from microorganisms that can cause foodborne illness.

Food activists are concerned that some of the chemicals used by the food industry for disinfection can cause health issues for consumers. A prime example is the current discussion in Europe about ‘American chlorine chicken’. …

Berger goes on to highlight the research being conducted at the Harvard T. Chan School of Public Health (Harvard University). The team announced a new technique called Engineered Water Nanostructures (EWNS), which is generated by electrospraying water. The team published this paper in 2014,

A chemical free, nanotechnology-based method for airborne bacterial inactivation using engineered water nanostructures by Georgios Pyrgiotakis, James McDevitt, Andre Bordini, Edgar Diaz, Ramon Molina, Christa Watson, Glen Deloid, Steve Lenard, Natalie Fix, Yosuke Mizuyama, Toshiyuki Yamauchi, Joseph Brain and Philip Demokritou. Environ. Sci.: Nano, 2014,1, 15-26 DOI: 10.1039/C3EN00007A

First published online 28 Nov 2013

This paper is open access.

More recently, the team has proved the efficacy of this technique on stainless steel surfaces and tomatoes. A Feb. 25, 2015 Harvard T. Chan School of Public Health news release provides information about the costs of foodborne diseases and goes on to describe the technique and the latest experiments,

The burden of foodborne diseases worldwide is huge, with serious economic and public health consequences. The U.S. Department of Agriculture’s (USDA’s) Economic Research Service reported in 2014 that foodborne illnesses are costing the economy more than $15.6 billion and about 53,245 Americans visit the hospital annually due to foodborne illnesses. The food industry is in search of effective intervention methods that can be applied form “farm to fork” to ensure the safety of the food chain and be consumer and environment friendly at the same time.

Researchers at the Center for Nanotechnology and Nanotoxicology of the Harvard T. Chan School of Public Health are currently exploring the effectiveness of a nanotechnology based, chemical free, intervention method for the inactivation of foodborne and spoilage microorganisms on fresh produce and on food production surfaces. This method utilizes Engineered Water Nanostructures (EWNS) generated by electrospraying of water. EWNS possess unique properties; they are 25 nm in diameter, remain airborne in indoor conditions for hours, contain Reactive Oxygen Species (ROS), have very strong surface charge (on average 10e/structure) and have the ability to interact and inactivate pathogens by destroying their membrane.

In a study funded by the USDA and just published this week in the premier Environmental Science and Technology journal, the efficacy of these tiny water nanodroplets, in inactivating representative foodborne pathogens such as Escherichia coli, Salmonella enterica and Listeria innocua, on stainless steel surfaces and on tomatoes, was assessed showing significant log reductions in inactivation of select food pathogens. These promising results could open up the gateway for further exploration into the dynamics of this method in the battle against foodborne disease. More importantly this novel, chemical-free, cost effective and environmentally friendly intervention method holds great potential for development and application in the food industry, as a ‘green’ alternative to existing inactivation methods.

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

Inactivation of Foodborne Microorganisms Using Engineered Water Nanostructures (EWNS) by Georgios Pyrgiotakis, Archana Vasanthakumar, Ya Gao, Mary Eleftheriadou, Eduardo Toledo, Alice DeAraujo, James McDevitt, Taewon Han, Gediminas Mainelis, Ralph Mitchell, and Philip Demokritou. Environ. Sci. Technol., Article ASAP DOI: 10.1021/es505868a Publication Date (Web): February 19, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall. The researchers have made this image illustrating a ‘water shell’s’ effect on a bacterium located on a tomato,

Courtesy: Researchers and the American Chemical Society

Courtesy: Researchers and the American Chemical Society

I’m not sure how chemical companies are going to feel but this is very exciting news. Still, one has to wonder just how much water this technique would require for full scale adoption and would it be reusable?

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.

Getting up to the size of a dust speck, the first ‘large’ self-assembling DNA crystals

An Oct. 19, 2014 news item on ScienceDaily describes the latest developments in ‘DNA nanotechnology’ research at the Wyss Institute for Biologically Inspired Engineering at Harvard University,

DNA has garnered attention for its potential as a programmable material platform that could spawn entire new and revolutionary nanodevices in computer science, microscopy, biology, and more. Researchers have been working to master the ability to coax DNA molecules to self assemble into the precise shapes and sizes needed in order to fully realize these nanotechnology dreams.

For the last 20 years, scientists have tried to design large DNA crystals with precisely prescribed depth and complex features — a design quest just fulfilled by a team at Harvard’s Wyss Institute for Biologically Inspired Engineering. The team built 32 DNA crystals with precisely-defined depth and an assortment of sophisticated three-dimensional (3D) features, an advance reported in Nature Chemistry.

It seems a bit of a misleading for the Wyss Institute to state the ‘team built’ the DNA crystals as they are self-assembling according to this Oct. 19, 2014 Wyss Institute news release (also on EurekAlert), which originated the news item,

The team used their “DNA-brick self-assembly” method, which was first unveiled in a 2012 Science publication when they created more than 100 3D complex nanostructures about the size of viruses. The newly-achieved periodic crystal structures are more than 1000 times larger than those discrete DNA brick structures, sizing up closer to a speck of dust, which is actually quite large in the world of DNA nanotechnology.

“We are very pleased that our DNA brick approach has solved this challenge,” said senior author and Wyss Institute Core Faculty member Peng Yin, Ph.D., who is also an Associate Professor of Systems Biology at Harvard Medical School, “and we were actually surprised by how well it works.”

The news release goes on to describe some of the issues with other self-assembly methods along with more details about the ‘DNA brick’ approach,

Scientists have struggled to crystallize complex 3D DNA nanostructures using more conventional self-assembly methods. The risk of error tends to increase with the complexity of the structural repeating units and the size of the DNA crystal to be assembled.

The DNA brick method uses short, synthetic strands of DNA that work like interlocking Lego® bricks to build complex structures. Structures are first designed using a computer model of a molecular cube, which becomes a master canvas. Each brick is added or removed independently from the 3D master canvas to arrive at the desired shape – and then the design is put into action: the DNA strands that would match up to achieve the desired structure are mixed together and self assemble to achieve the designed crystal structures.

“Therein lies the key distinguishing feature of our design strategy—its modularity,” said co-lead author Yonggang Ke, Ph.D., formerly a Wyss Institute Postdoctoral Fellow and now an assistant professor at the Georgia Institute of Technology and Emory University. “The ability to simply add or remove pieces from the master canvas makes it easy to create virtually any design.”

The modularity also makes it relatively easy to precisely define the crystal depth. “This is the first time anyone has demonstrated the ability to rationally design crystal depth with nanometer precision, up to 80 nm in this study,” Ke said. In contrast, previous two-dimensional DNA lattices are typically single-layer structures with only 2 nm depth.

“DNA crystals are attractive for nanotechnology applications because they are comprised of repeating structural units that provide an ideal template for scalable design features”, said co-lead author graduate student Luvena Ong.

Furthermore, as part of this study the team demonstrated the ability to position gold nanoparticles into prescribed 2D architectures less than two nanometers apart from each other along the crystal structure – a critical feature for future quantum devices and a significant technical advance for their scalable production, said co-lead author Wei Sun, Ph.D., Wyss Institute Postdoctoral Fellow.

“My preconceived notions of the limitations of DNA have been consistently shattered by our new advances in DNA nanotechnology,” said William Shih, Ph.D., who is co-author of the study and a Wyss Institute Founding Core Faculty member, as well as Associate Professor in the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School and the Department of Cancer Biology at the Dana-Farber Cancer Institute. “DNA nanotechnology now makes it possible for us to assemble, in a programmable way, prescribed structures rivaling the complexity of many molecular machines we see in Nature.”

“Peng’s team is using the DNA-brick self-assembly method to build the foundation for the new landscape of DNA nanotechnology at an impressive pace,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. “What have been mere visions of how the DNA molecule could be used to advance everything from the semiconductor industry to biophysics are fast becoming realities.”

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

DNA brick crystals with prescribed depths by Yonggang Ke, Luvena L. Ong, Wei Sun, Jie Song, Mingdong Dong, William M. Shih, & Peng Yin. Nature Chemistry (2014) doi:10.1038/nchem.2083 Published online 19 October 2014

This paper is behind a paywall.

SLIPS (Slippery Liquid-Infused Porous Surfaces) technology repels blood and bacteria from medical devices

Researchers at Harvard University’s Wyss Institute for Biologically Inspired Engineering have developed a coating for medical devices that helps to address some of these devices’ most  troublesome aspects. From an Oct. 12, 2014 news item on ScienceDaily,

From joint replacements to cardiac implants and dialysis machines, medical devices enhance or save lives on a daily basis. However, any device implanted in the body or in contact with flowing blood faces two critical challenges that can threaten the life of the patient the device is meant to help: blood clotting and bacterial infection.

A team of Harvard scientists and engineers may have a solution. They developed a new surface coating for medical devices using materials already approved by the Food and Drug Administration (FDA). The coating repelled blood from more than 20 medically relevant substrates the team tested — made of plastic to glass and metal — and also suppressed biofilm formation in a study reported in Nature Biotechnology. But that’s not all.

The team implanted medical-grade tubing and catheters coated with the material in large blood vessels in pigs, and it prevented blood from clotting for at least eight hours without the use of blood thinners such as heparin. Heparin is notorious for causing potentially lethal side-effects like excessive bleeding but is often a necessary evil in medical treatments where clotting is a risk.

“Devising a way to prevent blood clotting without using anticoagulants is one of the holy grails in medicine,” said Don Ingber, M.D., Ph.D., Founding Director of Harvard’s Wyss Institute for Biologically Inspired Engineering and senior author of the study. Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children’s Hospital, as well as professor of bioengineering at Harvard School of Engineering and Applied Sciences (SEAS).

An Oct. 12, 2014 Wyss Institute news release (also on EurekAlert), which originated the news item, describes the inspiration for this work,

The idea for the coating evolved from SLIPS, a pioneering surface technology developed by coauthor Joanna Aizenberg, Ph.D., who is a Wyss Institute Core Faculty member and the Amy Smith Berylson Professor of Materials Science at Harvard SEAS. SLIPS stands for Slippery Liquid-Infused Porous Surfaces. Inspired by the slippery surface of the carnivorous pitcher plant, which enables the plant to capture insects, SLIPS repels nearly any material it contacts. The liquid layer on the surface provides a barrier to everything from ice to crude oil and blood.

“Traditional SLIPS uses porous, textured surface substrates to immobilize the liquid layer whereas medical surfaces are mostly flat and smooth – so we further adapted our approach by capitalizing on the natural roughness of chemically modified surfaces of medical devices,” said Aizenberg, who leads the Wyss Institute’s Adaptive Materials platform. “This is yet another incarnation of the highly customizable SLIPS platform that can be designed to create slippery, non-adhesive surfaces on any material.”

The Wyss team developed a super-repellent coating that can be adhered to existing, approved medical devices. In a two-step surface-coating process, they chemically attached a monolayer of perfluorocarbon, which is similar to Teflon. Then they added a layer of liquid perfluorocarbon, which is widely used in medicine for applications such as liquid ventilation for infants with breathing challenges, blood substitution, eye surgery, and more. The team calls the tethered perfluorocarbon plus the liquid layer a Tethered-Liquid Perfluorocarbon surface, or TLP for short.

In addition to working seamlessly when coated on more than 20 different medical surfaces and lasting for more than eight hours to prevent clots in a pig under relatively high blood flow rates without the use of heparin, the TLP coating achieved the following results:

  • TLP-treated medical tubing was stored for more than a year under normal temperature and humidity conditions and still prevented clot formation
  • The TLP surface remained stable under the full range of clinically relevant physiological shear stresses, or rates of blood flow seen in catheters and central lines, all the way up to dialysis machines
  • It repelled the components of blood that cause clotting (fibrin and platelets)
  • When bacteria called Pseudomonas aeruginosa were grown in TLP-coated medical tubing for more than six weeks, less than one in a billion bacteria were able to adhere. Central lines coated with TLP significantly reduce sepsis from Central-Line Mediated Bloodstream Infections (CLABSI). (Sepsis is a life-threatening blood infection caused by bacteria, and a significant risk for patients with implanted medical devices.)

Out of sheer curiosity, the researchers even tested a TLP-coated surface with a gecko – the superstar of sticking whose footpads contain many thousands of hairlike structures with tremendous adhesive strength. The gecko was unable to hold on.

“We were wonderfully surprised by how well the TLP coating worked, particularly in vivo without heparin,” said one of the co-lead authors, Anna Waterhouse, Ph.D., a Wyss Institute Postdoctoral Fellow. “Usually the blood will start to clot within an hour in the extracorporeal circuit, so our experiments really demonstrate the clinical relevance of this new coating.”

While most of the team’s demonstrations were performed on medical devices such as catheters and perfusion tubing using relatively simple setups, they say there is a lot more on the horizon.

“We feel this is just the beginning of how we might test this for use in the clinic,” said co-lead author Daniel Leslie, Ph.D., a Wyss Institute Staff Scientist, who aims to test it on more complex systems such as dialysis machines and ECMO, a machine used in the intensive care unit to help critically ill patients breathe.

I first featured SLIPS technology in a Jan. 15, 2014 post about its possible use for stain-free, self-cleaning clothing. This Wyss Institute video about the latest work featuring the use of  SLIPS technology in medical devices also describes its possible use in pipelines and airplanes,

You can find research paper with this link,

A bioinspired omniphobic surface coating on medical devices prevents thrombosis and biofouling by Daniel C Leslie, Anna Waterhouse, Julia B Berthet, Thomas M Valentin, Alexander L Watters, Abhishek Jain, Philseok Kim, Benjamin D Hatton, Arthur Nedder, Kathryn Donovan, Elana H Super, Caitlin Howell, Christopher P Johnson, Thy L Vu, Dana E Bolgen, Sami Rifai, Anne R Hansen, Michael Aizenberg, Michael Super, Joanna Aizenberg, & Donald E Ingber. Nature Biotechnology (2014) doi:10.1038/nbt.3020 Published online 12 October 2014

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

Asthma on a chip

Harvard University’s Wyss Institute for Biologically Inspired Engineering has found a way to mimic the lung’s muscle action when an asthma attack is being experienced according to a Sept. 23, 2014 news item on Nanowerk,

The majority of drugs used to treat asthma today are the same ones that were used 50 years ago. New drugs are urgently needed to treat this chronic respiratory disease, which causes nearly 25 million people in the United States alone to wheeze, cough, and find it difficult at best to take a deep breath.

But finding new treatments is tough: asthma is a patient-specific disease, so what works for one person doesn’t necessarily work for another, and the animal models traditionally used to test new drug candidates often fail to mimic human responses–costing tremendous money and time.

Hope for healthier airways may be on the horizon thanks to a Harvard University team that has developed a human airway muscle-on-a-chip that could be used to test new drugs because it accurately mimics the way smooth muscle contracts in the human airway, under normal circumstances and when exposed to asthma triggers. [emphasis mine]

A Sept. 23, 2014 Wyss Institute news release (also on EurekAlert*), which originated the news item, provides more details about the technology and its advantages,

The chip, a soft polymer well that is mounted on a glass substrate, contains a planar array of microscale, engineered human airway muscles, designed to mimic the laminar structure of the muscular layers of the human airway.

To mimic a typical allergic asthma response, the team first introduced interleukin-13 (IL-13) to the chip. IL-13 is a natural protein often found in the airway of asthmatic patients that mediates the response of smooth muscle to an allergen.

Then they introduced acetylcholine, a neurotransmitter that causes smooth muscle to contract. Sure enough, the airway muscle on the chip hypercontracted – and the soft chip curled up – in response to higher doses of the neurotransmitter.

They achieved the reverse effect as well and triggered the muscle to relax using drugs called β-agonists, which are used in inhalers.

Significantly, they were able to measure the contractile stress of the muscle tissue as it responded to varying doses of the drugs, said lead author Alexander Peyton Nesmith, a Ph.D./M.D. student at Harvard SEAS and the University of Alabama at Birmingham. “Our chip offers a simple, reliable and direct way to measure human responses to an asthma trigger,” he said.

The team then investigated what happened on a cellular level in response to the IL-13 and confirmed, for example, that the smooth muscle cells grew larger in the presence of IL-13 over time – a structural hallmark of the airways in asthma patients as well. They also documented an increased alignment of actin fibers within smooth muscle cells, which is consistent with the muscle in the airway of asthma patients. Actin fibers are super-thin cellular components involved in muscle contraction.

Next they observed how IL-13 changes the expression of contractile proteins called RhoA proteins, which have been implicated in the asthmatic response, although the details of their activation and signaling have remained elusive. To do this they introduced a drug called HA1077, which is not currently used to treat asthmatic patients – but targets the RhoA pathway. It turns out that the drug made the asthmatic tissue on the chip less sensitive to the asthma trigger – and preliminary tests indicated that using a combined therapy of HA1077 plus a currently approved asthma drug worked better than the single drug alone.

“Asthma is one of the top reasons for trips to the emergency room – particularly for children, and a large segment of the asthmatic population doesn’t respond to currently available treatments,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. “The airway muscle-on-a-chip provides an important and exciting new tool for discovering new therapeutic agents.”

The scientists have provided an illustration of healthy and asthmatic airways,

Schematic comparing a healthy airway (few immune cells, normal airway diameter) to an asthmatic airway (many immune cells, constricted airway). Credit: Harvard's Wyss Institute and Harvard SEAS [School of Engineering and Applied Sciences]

Schematic comparing a healthy airway (few immune cells, normal airway diameter) to an asthmatic airway (many immune cells, constricted airway). Credit: Harvard’s Wyss Institute and Harvard SEAS [School of Engineering and Applied Sciences]

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

Human airway musculature on a chip: an in vitro model of allergic asthmatic bronchoconstriction and bronchodilation by Alexander Peyton Nesmith, Ashutosh Agarwal, Megan Laura McCain and Kevin Kit Parker.Lab Chip, 2014,14, 3925-3936 DOI: 10.1039/C4LC00688G First published online 05 Aug 2014

This paper is open access provided you have registered yourself for free at the site.

* EurekAlert link added Sept. 24, 2014.

Cyborgs (a presentation) at the American Chemical Society’s 248th meeting

There will be a plethora of chemistry news online over the next few days as the American Society’s (ACS) 248th meeting in San Francisco, CA from Aug. 10 -14, 2014 takes place. Unexpectedly, an Aug. 11, 2014 news item on Azonano highlights a meeting presentation focused on cyborgs,

No longer just fantastical fodder for sci-fi buffs, cyborg technology is bringing us tangible progress toward real-life electronic skin, prosthetics and ultraflexible circuits. Now taking this human-machine concept to an unprecedented level, pioneering scientists are working on the seamless marriage between electronics and brain signaling with the potential to transform our understanding of how the brain works — and how to treat its most devastating diseases.

An Aug. 10, 2014 ACS news release on EurekAlert provides more detail about the presentation (Note: Links have been removed),

“By focusing on the nanoelectronic connections between cells, we can do things no one has done before,” says Charles M. Lieber, Ph.D. “We’re really going into a new size regime for not only the device that records or stimulates cellular activity, but also for the whole circuit. We can make it really look and behave like smart, soft biological material, and integrate it with cells and cellular networks at the whole-tissue level. This could get around a lot of serious health problems in neurodegenerative diseases in the future.”

These disorders, such as Parkinson’s, that involve malfunctioning nerve cells can lead to difficulty with the most mundane and essential movements that most of us take for granted: walking, talking, eating and swallowing.

Scientists are working furiously to get to the bottom of neurological disorders. But they involve the body’s most complex organ — the brain — which is largely inaccessible to detailed, real-time scrutiny. This inability to see what’s happening in the body’s command center hinders the development of effective treatments for diseases that stem from it.

By using nanoelectronics, it could become possible for scientists to peer for the first time inside cells, see what’s going wrong in real time and ideally set them on a functional path again.

For the past several years, Lieber has been working to dramatically shrink cyborg science to a level that’s thousands of times smaller and more flexible than other bioelectronic research efforts. His team has made ultrathin nanowires that can monitor and influence what goes on inside cells. Using these wires, they have built ultraflexible, 3-D mesh scaffolding with hundreds of addressable electronic units, and they have grown living tissue on it. They have also developed the tiniest electronic probe ever that can record even the fastest signaling between cells.

Rapid-fire cell signaling controls all of the body’s movements, including breathing and swallowing, which are affected in some neurodegenerative diseases. And it’s at this level where the promise of Lieber’s most recent work enters the picture.

In one of the lab’s latest directions, Lieber’s team is figuring out how to inject their tiny, ultraflexible electronics into the brain and allow them to become fully integrated with the existing biological web of neurons. They’re currently in the early stages of the project and are working with rat models.

“It’s hard to say where this work will take us,” he says. “But in the end, I believe our unique approach will take us on a path to do something really revolutionary.”

Lieber acknowledges funding from the U.S. Department of Defense, the National Institutes of Health and the U.S. Air Force.

I first covered Lieber’s work in an Aug. 27, 2012 posting  highlighting some good descriptions from Lieber and his colleagues of their work. There’s also this Aug. 26, 2012 article by Peter Reuell in the Harvard Gazette (featuring a very good technical description for someone not terribly familiar with the field but able to grasp some technical information while managing their own [mine] ignorance). The posting and the article provide details about the foundational work for Lieber’s 2014 presentation at the ACS meeting.

Lieber will be speaking next at the IEEE (Institute for Electrical and Electronics Engineers) 14th International Conference on Nanotechnology sometime between August 18 – 21, 2014 in Toronto, Ontario, Canada.

As for some of Lieber’s latest published work, there’s more information in my Feb. 20, 2014 posting which features a link to a citation for the paper (behind a paywall) in question.

Let’s make our turbine blades really big (greater than 75 metres) with new nanocomposite

The is a story about balsa wood, wind farms, turbine blades, and nanocomposites according to a June 25, 2014 news item on ScienceDaily,

In wind farms across North America and Europe, sleek turbines equipped with state-of-the-art technology convert wind energy into electric power. But tucked inside the blades of these feats of modern engineering is a decidedly low-tech core material: balsa wood.

Like other manufactured products that use sandwich panel construction to achieve a combination of light weight and strength, turbine blades contain carefully arrayed strips of balsa wood from Ecuador, which provides 95 percent of the world’s supply.

For centuries, the fast-growing balsa tree has been prized for its light weight and stiffness relative to density. But balsa wood is expensive and natural variations in the grain can be an impediment to achieving the increasingly precise performance requirements of turbine blades and other sophisticated applications.

As turbine makers produce ever-larger blades — the longest now measure 75 meters, almost matching the wingspan of an Airbus A380 jetliner — they must be engineered to operate virtually maintenance-free for decades. In order to meet more demanding specifications for precision, weight, and quality consistency, manufacturers are searching for new sandwich construction material options.

Now, using a cocktail of fiber-reinforced epoxy-based thermosetting resins and 3D extrusion printing techniques, materials scientists at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have developed cellular composite materials of unprecedented light weight and stiffness.

A June 25, 2014 Harvard University news release (also on EurekAlert), which originated the news item, goes on to describe the new technology in more detail while throwing 3D printing into the mix,

Until now, 3D printing has been developed for thermo plastics and UV-curable resins—materials that are not typically considered as engineering solutions for structural applications. “By moving into new classes of materials like epoxies, we open up new avenues for using 3D printing to construct lightweight architectures,” says principal investigator Jennifer A. Lewis, the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS. “Essentially, we are broadening the materials palate for 3D printing.”

“Balsa wood has a cellular architecture that minimizes its weight since most of the space is empty and only the cell walls carry the load. It therefore has a high specific stiffness and strength,” explains Lewis, who in addition to her role at Harvard SEAS is also a Core Faculty Member at the Wyss Institute. “We’ve borrowed this design concept and mimicked it in an engineered composite.”

Lewis and Brett G. Compton, a former postdoctoral fellow in her group, developed inks of epoxy resins, spiked with viscosity-enhancing nanoclay platelets and a compound called dimethyl methylphosphonate, and then added two types of fillers: tiny silicon carbide “whiskers” and discrete carbon fibers. Key to the versatility of the resulting fiber-filled inks is the ability to control the orientation of the fillers.

The direction that the fillers are deposited controls the strength of the materials (think of the ease of splitting a piece of firewood lengthwise versus the relative difficulty of chopping on the perpendicular against the grain).

Lewis and Compton have shown that their technique yields cellular composites that are as stiff as wood, 10 to 20 times stiffer than commercial 3D-printed polymers, and twice as strong as the best printed polymer composites. The ability to control the alignment of the fillers means that fabricators can digitally integrate the composition, stiffness, and toughness of an object with its design.

“This paper demonstrates, for the first time, 3D printing of honeycombs with fiber-reinforced cell walls,” said Lorna Gibson, a professor of materials science and mechanical engineering at the Massachusetts Institute of Technology and one of world’s leading experts in cellular composites, who was not involved in this research. “Of particular significance is the way that the fibers can be aligned, through control of the fiber aspect ratio—the length relative to the diameter—and the nozzle diameter. This marks an important step forward in designing engineering materials that mimic wood, long known for its remarkable mechanical properties for its weight.”

“As we gain additional levels of control in filler alignment and learn how to better integrate that orientation into component design, we can further optimize component design and improve materials efficiency,” adds Compton, who is now a staff scientist in additive manufacturing at Oak Ridge National Laboratory. “Eventually, we will be able to use 3D printing technology to change the degree of fiber filler alignment and local composition on the fly.”

The work could have applications in many fields, including the automotive industry where lighter materials hold the key to achieving aggressive government-mandated fuel economy standards. According to one estimate, shedding 110 pounds from each of the 1 billion cars on the road worldwide could produce $40 billion in annual fuel savings.

3D printing has the potential to radically change manufacturing in other ways too. Lewis says the next step will be to test the use of thermosetting resins to create different kinds of architectures, especially by exploiting the technique of blending fillers and precisely aligning them. This could lead to advances not only in structural materials, but also in conductive composites.

Previously, Lewis has conducted groundbreaking research in the 3D printing of tissue constructs with vasculature and lithium-ion microbatteries.

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

3D-Printing of Lightweight Cellular Composites by Brett G. Compton and Jennifer A. Lewis. Advanced Materials DOI: 10.1002/adma.201401804 Article first published online: 18 JUN 2014

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

This paper is behind a paywall.