Tag Archives: US

What colour is your diagnosis?

Mark Lorch has written an April 16, 2015 piece for The Conversation (h/t the Guardian’s April 17, 2015 posting) about a very appealing approach to diagnostics (Note: A link has been removed),

If you’ve ever sat opposite a doctor and wondered what she was scribbling on her notepad, the answer may soon not only be medical notes on your condition, but real-time chemical preparations for an instant diagnostic test.

Thanks to the work of a team of researchers from California Polytechnic State University, recently published in the journal Lab on a Chip, chemicals formed into pencils can be made to react with one another by simply drawing with them on paper. The team may have taken inspiration from colouring books for their take on a chemical toolkit, but their approach could make carrying out simple but common diagnostic tests based on chemical reactions – for example diabetes, HIV, or tests for environmental pollutants – much easier.

Here’s a picture of the pens,

ReagentPencilsDiagnostics

Courtesy: Lab on a Chip

Lorch provides a good description of the technology giving descriptions of reagents and paper-based microfluidics, as well as, describing how the researchers turned the concept of colouring pencils into a diagnostic tool.

Lorch also provides a description of a specific test (Note: Links have been removed),

The team demonstrated a potential use of the reagent pencil technique by using it in place of a common test used by diabetics to check their blood glucose levels, which involves reacting a pinprick blood sample with a chemical solution and examining the result.

One pencil was constructed with a mixture of enzymes, one called horseradish peroxidase (HRP) and the other glucose oxidase (GOx). A second pencil contained a reagent called ABTS. When combined in the presence of glucose these react together to give a blue-coloured product. Comparing the results from their pencils on the pad with the more traditional dropper method used by diabetics the team found the results were identical.

This new ‘pencil kit’ diagnostic technology is easy to use and features a big improvement over the current diagnostic tests,

This is of course extremely easy to set up. Traditional diagnostic tests require training, while this pad and pencil system requires no more than skill than required to colour within the lines. The reagents are extremely stable once made into pencils – usually they would degrade in a matter of days as liquids, limiting how and where the tests can be made. However the reagent pencils showed no sign of degrading after two months.

Being able to use the pencils for two months as opposed to liquids that remain viable for a few days? That’s a huge jump and it makes me wonder about using these kits in harsh conditions such as desert climates and/or emergency situations. Materials that don’t need to be refrigerated and could be used for up to two months and don’t require intensive training could be very helpful. Lorch suggests some other possibilities as well,

… There’s scope to monitor environmental pollutants, carry out diagnostic tests in remote locations – not to mention teach chemistry in primary schools.

Here’s a link to and a citation for the study on the ‘colouring pencil kit’,

Reagent pencils: a new technique for solvent-free deposition of reagents onto paper-based microfluidic devices by Haydn T. Mitchell, Isabelle C. Noxon, Cory A. Chaplan, Samantha J. Carlton, Cheyenne H. Liu, Kirsten A. Ganaja, Nathaniel W. Martinez, Chad E. Immoos, Philip J. Costanzo, and Andres W. Martinez. Lab Chip, 2015, Advance Article DOI: 10.1039/C5LC00297D First published online 08 Apr 2015

This paper is open access but you do have to register on the site unless you have another means of access.

Reversing Parkinson’s type symptoms in rats

Indian scientists have developed a technique for delivering drugs that could reverse Parkinson-like symptoms according to an April 22, 2015 news item on Nanowerk (Note: A link has been removed),

As baby boomers age, the number of people diagnosed with Parkinson’s disease is expected to increase. Patients who develop this disease usually start experiencing symptoms around age 60 or older. Currently, there’s no cure, but scientists are reporting a novel approach that reversed Parkinson’s-like symptoms in rats.

Their results, published in the journal ACS Nano (“Trans-Blood Brain Barrier Delivery of Dopamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Rats”), could one day lead to a new therapy for human patients.

An April 22, 2015 American Chemical Society press pac news release (also on EurekAlert), which originated the news item, describes the problem the researchers were solving (Note: Links have been removed),

Rajnish Kumar Chaturvedi, Kavita Seth, Kailash Chand Gupta and colleagues from the CSIR-Indian Institute of Toxicology Research note that among other issues, people with Parkinson’s lack dopamine in the brain. Dopamine is a chemical messenger that helps nerve cells communicate with each other and is involved in normal body movements. Reduced levels cause the shaking and mobility problems associated with Parkinson’s. Symptoms can be relieved in animal models of the disease by infusing the compound into their brains. But researchers haven’t yet figured out how to safely deliver dopamine directly to the human brain, which is protected by something called the blood-brain barrier that keeps out pathogens, as well as many medicines. Chaturvedi and Gupta’s team wanted to find a way to overcome this challenge.

The researchers packaged dopamine in biodegradable nanoparticles that have been used to deliver other therapeutic drugs to the brain. The resulting nanoparticles successfully crossed the blood-brain barrier in rats, released its dopamine payload over several days and reversed the rodents’ movement problems without causing side effects.

The authors acknowledge funding from the Indian Department of Science and Technology as Woman Scientist and Ramanna Fellow Grant, and the Council of Scientific and Industrial Research (India).

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

Trans-Blood Brain Barrier Delivery of Dopamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Rats by Richa Pahuja, Kavita Seth, Anshi Shukla, Rajendra Kumar Shukla, Priyanka Bhatnagar, Lalit Kumar Singh Chauhan, Prem Narain Saxena, Jharna Arun, Bhushan Pradosh Chaudhari, Devendra Kumar Patel, Sheelendra Pratap Singh, Rakesh Shukla, Vinay Kumar Khanna, Pradeep Kumar, Rajnish Kumar Chaturvedi, and Kailash Chand Gupta. ACS Nano, Article ASAP DOI: 10.1021/nn506408v Publication Date (Web): March 31, 2015
Copyright © 2015 American Chemical Society

This paper is open access.

Another recent example of breaching the blood-brain barrier, coincidentally, in rats, can be found in my Dec. 24, 2014 titled: Gelatin nanoparticles for drug delivery after a stroke. Scientists are also trying to figure out the the blood-brain barrier operates in the first place as per this April 22, 2015 University of Pennsylvania news release on EurekAlert titled, Penn Vet, Montreal and McGill researchers show how blood-brain barrier is maintained (University of Pennsylvania School of Veterinary Medicine, University of Montreal or Université de Montréal, and McGill University). You can find out more about CSIR-Indian Institute of Toxicology Research here.

Outcomes for US-European Union bridging Nano environment, health, and safety (EHS) research workshop

According to Lynn Bergeson in an April 14, 2015 news item on Nanotechnology Now, a US-European Union (EU) workshop on nanosafety has published a document,

The National Nanotechnology Initiative (NNI) published on March 23, 2015, the outcomes of the March 12-13, 2015, joint workshop held by the U.S. and the European Union (EU), “Bridging NanoEHS Research Efforts.” …

A US National Nanotechnology Initiative (NNI) ??, ??, 2015 notice on the nano.gov site provides more details,

Workshop participants reviewed progress toward COR [communities of research] goals and objectives, shared best practices, and identified areas for cross-COR collaboration.  To address new challenges the CORs were realigned and expanded with the addition of a COR on nanotechnology characterization. The seven CORs now address:

Characterization
Databases and Computational Modeling
Exposure through Product Life
EcoToxicity
Human Toxicity
Risk Assessment
Risk Management and Control

The CORs support the shared goal of responsible nanotechnology development as outlined in the U.S. National Nanotechnology Initiative EHS Research Strategy, and the research strategy of the EU NanoSafety Cluster. The CORs directly address several priorities described in the documents above, including the creation of a comprehensive nanoEHS knowledge base and international cooperation on the development of best practices and consensus standards.

The CORs are self-run, with technical support provided by the European Commission and the U.S. National Nanotechnology Coordination Office. Each Community has European and American co-chairs who convene meetings and teleconferences, guide the discussions, and set the group’s agenda. Participation in the CORs is free and open to any interested individuals. More information is available at www.us-eu.org.

The workshop was organized by the European Commission and the U.S. National Nanotechnology Initiative under the auspices of the agreement for scientific and technological cooperation between the European Union and the United States.

Coincidentally, I received an April 13, 2015 notice about the European Commission’s NanoSafety Cluster’s Spring 2015 newsletter concerning their efforts but found no mention of the ‘bridging workshop’. Presumably, information was not available prior to the newsletter’s deadline.

In my April 8, 2014 posting about a US proposed rule for reporting nanomaterials, I included information about the US and its efforts to promote or participate in harmonizing the nano situation internationally. Scroll down about 35% of the way to find information about the Canada-U.S. Regulatory Cooperation Council (RCC) Nanotechnology Initiative, the Organisation for Economic Cooperation and Development (OECD) effort, and the International Organization for Standardization (ISO) effort.

3D printing soft robots and flexible electronics with metal alloys

This research comes from Purdue University (Indiana, US) which seems to be on a publishing binge these days. From an April 7, 2015 news item on Nanowerk,

New research shows how inkjet-printing technology can be used to mass-produce electronic circuits made of liquid-metal alloys for “soft robots” and flexible electronics.

Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. However, new manufacturing techniques must be developed before soft machines become commercially feasible, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University.

“We want to create stretchable electronics that might be compatible with soft machines, such as robots that need to squeeze through small spaces, or wearable technologies that aren’t restrictive of motion,” she said. “Conductors made from liquid metal can stretch and deform without breaking.”

A new potential manufacturing approach focuses on harnessing inkjet printing to create devices made of liquid alloys.

“This process now allows us to print flexible and stretchable conductors onto anything, including elastic materials and fabrics,” Kramer said.

An April 7, 2015 Purdue University news release (also on EurekAlert) by Emil Venere, which originated the news item, expands on the theme,

A research paper about the method will appear on April 18 [2015] in the journal Advanced Materials. The paper generally introduces the method, called mechanically sintered gallium-indium nanoparticles, and describes research leading up to the project. It was authored by postdoctoral researcher John William Boley, graduate student Edward L. White and Kramer.

A printable ink is made by dispersing the liquid metal in a non-metallic solvent using ultrasound, which breaks up the bulk liquid metal into nanoparticles. This nanoparticle-filled ink is compatible with inkjet printing.

“Liquid metal in its native form is not inkjet-able,” Kramer said. “So what we do is create liquid metal nanoparticles that are small enough to pass through an inkjet nozzle. Sonicating liquid metal in a carrier solvent, such as ethanol, both creates the nanoparticles and disperses them in the solvent. Then we can print the ink onto any substrate. The ethanol evaporates away so we are just left with liquid metal nanoparticles on a surface.”

After printing, the nanoparticles must be rejoined by applying light pressure, which renders the material conductive. This step is necessary because the liquid-metal nanoparticles are initially coated with oxidized gallium, which acts as a skin that prevents electrical conductivity.

“But it’s a fragile skin, so when you apply pressure it breaks the skin and everything coalesces into one uniform film,” Kramer said. “We can do this either by stamping or by dragging something across the surface, such as the sharp edge of a silicon tip.”

The approach makes it possible to select which portions to activate depending on particular designs, suggesting that a blank film might be manufactured for a multitude of potential applications.

“We selectively activate what electronics we want to turn on by applying pressure to just those areas,” said Kramer, who this year was awarded an Early Career Development award from the National Science Foundation, which supports research to determine how to best develop the liquid-metal ink.

The process could make it possible to rapidly mass-produce large quantities of the film.

Future research will explore how the interaction between the ink and the surface being printed on might be conducive to the production of specific types of devices.

“For example, how do the nanoparticles orient themselves on hydrophobic versus hydrophilic surfaces? How can we formulate the ink and exploit its interaction with a surface to enable self-assembly of the particles?” she said.

The researchers also will study and model how individual particles rupture when pressure is applied, providing information that could allow the manufacture of ultrathin traces and new types of sensors.

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

Nanoparticles: Mechanically Sintered Gallium–Indium Nanoparticles by John William Boley, Edward L. White and Rebecca K. Kramer. Advanced Materials Volume 27, Issue 14, page 2270, April 8, 2015 DOI: 10.1002/adma.201570094 Article first published online: 7 APR 2015

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

This article is behind a paywall.

Nature’s patterns reflected in gold nanoparticles

A 133 atom gold nanoparticle bears a resemblance to the Milky Way and to DNA’s (deoxyribonucleic acid) double helix according to an April 9, 2015 news item on ScienceDaily,

Our world is full of patterns, from the twist of a DNA molecule to the spiral of the Milky Way. New research from Carnegie Mellon chemists has revealed that tiny, synthetic gold nanoparticles exhibit some of nature’s most intricate patterns.

Unveiling the kaleidoscope of these patterns was a Herculean task, and it marks the first time that a nanoparticle of this size has been crystallized and its structure mapped out atom by atom. The researchers report their work in the March 20  [2015] issue of Science Advances.

“As you broadly think about different research areas or even our everyday lives, these kinds of patterns, these hierarchical patterns, are universal,” said Rongchao Jin, associate professor of chemistry. “Our universe is really beautiful and when you see this kind of information in something as small as a 133-atom nanoparticle and as big as the Milky Way, it’s really amazing.”

An April 8, 2015 Carnegie Mellon University news release (also on EurekAlert but dated April 9) by Jocelyn Duffy, which originated the news release, offers a description of gold nanoparticles along with details about the research,

Gold nanoparticles, which can vary in size from 1 to 100 nanometers, are a promising technology that has applications in a wide range of fields including catalysis, electronics, materials science and health care. But, in order to use gold nanoparticles in practical applications, scientists must first understand the tiny particles’ structure.

“Structure essentially determines the particle’s properties, so without knowing the structure, you wouldn’t be able to understand the properties and you wouldn’t be able to functionalize them for specific applications,” said Jin, an expert in creating atomically precise gold nanoparticles.

With this latest research, Jin and his colleagues, including graduate student Chenjie Zeng, have solved the structure of a nanoparticle, Au133, made up of 133 gold atoms and 52 surface-protecting molecules—the biggest nanoparticle structure ever resolved with X-ray crystallography. While microscopy can reveal the size, shape and the atomic lattice of nanoparticles, it can’t discern the surface structure. X-ray crystallography can, by mapping out the position of every atom on the nanoparticles’ surface and showing how they bond with the gold core. Knowing the surface structure is key to using the nanoparticles for practical applications, such as catalysis, and for uncovering fundamental science, such as the basis of the particle’s stability.

The crystal structure of the Au133 nanoparticle divulged many secrets.

“With X-ray crystallography, we were able to see very beautiful patterns, which was a very exciting discovery. These patterns only show up when the nanoparticle size becomes big enough,” Jin said.

During production, the Au133 particles self-assemble into three layers within each particle: the gold core, the surface molecules that protect it and the interface between the two. In the crystal structure, Zeng discovered that the gold core is in the shape of an icosahedron. At the interface between the core and the surface-protecting molecules is a layer of sulfur atoms that bind with the gold atoms. The sulfur-gold-sulfur combinations stack into ladder-like helical structures. Finally, attached to the sulfur molecules is an outer layer of surface-protecting molecules whose carbon tails self-assemble into fourfold swirls.

“The helical features remind us of a DNA double helix and the rotating arrangement of the carbon tails is reminiscent of the way our galaxy is arranged. It’s really amazing,” Jin said.

These particular patterns are responsible for the high stability of Au133 compared to other sizes of gold nanoparticles. The researchers also tested the optical and electronic properties of Au133 and found that these gold nanoparticles are not metallic. [emphasis mine] Normally, gold is one of the best conductors of electrical current, but the size of Au133 is so small that the particle hasn’t yet become metallic. Jin’s group is currently testing the nanoparticles for use as catalysts, substances that can increase the rate of a chemical reaction.

*ETA April 14, 2015 at 9015 PDT: Coincidentally, researchers in Finland have been examining gold nanoparticles and the size at which they are considered metals and at which they are considered molecules (mentioned in my April 14, 2015 posting [Gold atoms: sometimes they’re a metal and sometimes they’re a molecule]).*

Getting back to patterns, the researchers have provided an A-ray image of Au133,

 Caption: The X-ray crystallographic structure of the gold nanoparticle is shown. Gold atoms = magenta; sulfur atoms = yellow; carbon atoms = gray; hydrogen atoms = white. Credit: Carnegie Mellon


Caption: The X-ray crystallographic structure of the gold nanoparticle is shown. Gold atoms = magenta; sulfur atoms = yellow; carbon atoms = gray; hydrogen atoms = white.
Credit: Carnegie Mellon

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

Structural patterns at all scales in a nonmetallic chiral Au133(SR)52 nanoparticle by Chenjie Zeng, Yuxiang Chen, Kristin Kirschbaum, Kannatassen Appavoo, Matthew Y. Sfeir, Rongchao Jin. Science Advances 20 Mar 2015: Vol. 1 no. 2 e1500045 DOI: 10.1126/sciadv.1500045

This paper appears to be open access.

Rubbery lettuce is a good thing

The lettuce we eat was cultivated from prickly lettuce, which is now considered a weed. That status may change if scientists at Washington State University (WSU) are successful with their research into the plant’s ability to produce rubber. From an April 6, 2014 WSU news release by Sylvia Kantor (also on EurekAlert),

Prickly lettuce, a common weed that has long vexed farmers, has potential as a new cash crop providing raw material for rubber production, according to Washington State University scientists.

Writing in the Journal of Agricultural and Food Chemistry, they describe regions in the plant’s genetic code linked to rubber production. The findings open the way for breeding for desired traits and developing a new crop source for rubber in the Pacific Northwest.

“I think there’s interest in developing a temperate-climate source of natural rubber,” said Ian Burke, a weed scientist at WSU and a study author. “It would be really great if prickly lettuce could become one of those crops.”

Here’s what prickly lettuce looks like,

Prickly lettuce, the wild relative of cultivated lettuce, is a potential source for the production of natural rubber. (Photo by Flickr user Jim Kennedy)

Prickly lettuce, the wild relative of cultivated lettuce, is a potential source for the production of natural rubber. (Photo by Flickr user Jim Kennedy)

Here’s a close-up of a prickly lettuce stem with sap,

The milky sap, or latex, of the plant could be used to produce rubber. (Photo by Jared Bell, WSU)

The milky sap, or latex, of the plant could be used to produce rubber. (Photo by Jared Bell, WSU)

Getting back to the prickly lettuce news release,

When the lettuce we eat and grow in our gardens bolts, a milky white sap bleeds from the stem. In prickly lettuce, the wild relative and ancestor of cultivated lettuce, this same substance could prove to be an economically viable source of natural rubber and help alleviate a worldwide threat to rubber production.

Natural rubber is the main ingredient for many everyday products, from boots to condoms to surgical gloves. Roughly 70 percent of the global supply of rubber is used in tires.

But more than half of rubber products are made from synthetic rubber derived from petrochemical sources. And the largest source of natural rubber, the Brazilian rubber tree, is threatened by disease.

Burke has reviewed many studies of prickly lettuce and its cultivated cousins, but one in particular gave him an idea. A study published in 2006 found that the latex in prickly lettuce was very similar to the polymers found in natural rubber.

“It occurred to me that we could grow the heck out of prickly lettuce in eastern Washington,” he said.

Genetic markers for desired traits

He knew that to develop a viable new crop for rubber production, he had to start by understanding the genetics of rubber production in the plant.

Burke, doctoral student Jared Bell and molecular plant scientist Michael Neff began their studies with two distinct samples of prickly lettuce collected from eastern Washington. These differed in their rubber content, leaf shape and tendency to bolt. The scientists were able to identify genetic markers not only for rubber content but for the way the plants grow, including the number of stems produced and bolting.

Sought-after traits in cultivated lettuce – like abundant leaves, a single stem and delayed bolting – are the exact opposite of traits desired for rubber production. Early bolting plants with multiple stems would allow for multiple harvests over the season and potentially maximize rubber yields.

Burke said that selecting for other traits, like water use efficiency, could allow prickly lettuce to be grown with minimal rainfall, meaning it could be grown in rotation with other crops.

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

Genetic and Biochemical Evaluation of Natural Rubber from Eastern Washington Prickly Lettuce (Lactuca serriola L.) by Jared L. Bell, Ian C. Burke, and Michael M. Neff. J. Agric. Food Chem., 2015, 63 (2), pp 593–602 DOI: 10.1021/jf503934v Publication Date (Web): December 16, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

Since graduating, Bell has become  associated with Dow Agrosciences.

FibeRio and VF Corporation want their nanofiber technology to lead in apparel and footwear markets

An April 8, 2015 news item on Azonano describes a new business partnership,

FibeRio Technology Corporation, the total nanofiber solutions company, today announced a strategic partnership with VF Corporation, a global leader in branded lifestyle apparel, footwear and accessories, to develop and commercialize next-generation, performance apparel fabrics leveraging FibeRio’s proprietary nanotechnology.

The partnership centers on FibeRio’s Forcespinning® technology platform and its ability to produce unique nanofiber material in high volumes. VF intends to incorporate FibeRio’s capabilities and expertise across its three Global Innovation Centers which focus on advancements in performance apparel, footwear and jeanswear.

An April 8, 2015 FibeRio news release provides more details, including these about the respective companies which help to contextualize the deal,

About FibeRio Technology Corporation
FibeRio is the efficiency and performance layer expert offering composite media improvement services including nanofiber membrane development, pilot production for limited launches and performance layer supply. The Fiber Engine series delivers on the industry’s need for high output, versatile, yet economic nanofiber production solutions. For more information visit www.fiberiotech.com

About VF Corporation
VF Corporation (NYSE: VFC) is a global leader in the design, manufacture, marketing and distribution of branded lifestyle apparel, footwear and accessories. The company’s highly diversified portfolio of 30 powerful brands spans numerous geographies, product categories, consumer demographics and sales channels, giving VF a unique industry position and the ability to create sustainable, long-term growth for our customers and shareholders. The company’s largest brands are The North Face®, Vans®, Timberland®, Wrangler®, Lee® and Nautica®. For more information, visit www.vfc.com.

There are the usual “we’re thrilled and about to do exciting things” quotes along with a dearth of details explaining how nanofibers are going to lead to higher performance,

“VF’s Global Innovation Center strategy is centered on the pursuit of disruptive design and materials that will meaningfully redefine the future of apparel and footwear for our consumers,” said Dan Cherian, Vice President, VF Global Innovation Centers. “Our partnership with FibeRio is a great step toward the co-development of proprietary, high-performance nanofiber materials that will help push the boundaries of performance and explore the creation of new apparel and footwear market categories.”

FibeRio CEO Ellery Buchanan stated, “We are excited to partner with VF Corporation on our Forcespinning-based advanced nanofiber textiles. VF’s long history of brand strength and operational excellence along with our leading commercial scale nanofiber production expertise creates an excellent opportunity to proactively shape the competitive landscape.”

Nanofibers’ higher surface area and smaller pore size improves the characteristics of fibrous material. This enables performance levels in any given application to be materially improved using significantly less material in the end product, which also allows for lighter weight and lower cost. [emphasis mine] FibeRio’s Forcespinning technology is the only technology platform capable of both commercial scale melt and solution spinning nanofibers. This provides a more sustainable method of production because melt spinning does not require solvents. [emphasis mine] Additionally, Forcespinning can be used to solution spin with vastly smaller amounts of solvents than traditional nanofiber production processes such as electrospinning.

Using less material could be considered a good thing, assuming it doesn’t mean that consumers need to purchase the item more frequently. The sustainability aspects such as no solvents or lesser amounts of solvent sound good unless increased demand means that a lesser amount becomes a greater amount.

I look forward to learning more as this partnership develops. One final note, I wonder if these folks are competitive with Teijin-Aramid (a Japanese-Dutch company in the Teijin Group), a company which does a lot of work with nanofibers last mentioned here in a Sept. 24, 2014 posting (scroll down about 60% of the way),

Still talking about textile fibres but on a completely different track, I received a news release this morning (Sept. 25, 2014) from Teijin Aramid about carbon nanotubes and fibres,

Researchers of Teijin Aramid, based in the Netherlands, and Rice University in the USA are awarded with the honorary ‘Paul Schlack Man-Made Fibers Prize’ for corporate-academic partnerships in fiber research. Their new super fibers are now driving innovation in aerospace, healthcare, automotive, and (smart) clothing.

I also found an April 12, 2012 post about Teijin Fibers (another Teijin Group company) and their work with nanofibers and golf gloves and athletic socks.

A more complex memristor: from two terminals to three for brain-like computing

Researchers have developed a more complex memristor device than has been the case according to an April 6, 2015 Northwestern University news release (also on EurekAlert),

Researchers are always searching for improved technologies, but the most efficient computer possible already exists. It can learn and adapt without needing to be programmed or updated. It has nearly limitless memory, is difficult to crash, and works at extremely fast speeds. It’s not a Mac or a PC; it’s the human brain. And scientists around the world want to mimic its abilities.

Both academic and industrial laboratories are working to develop computers that operate more like the human brain. Instead of operating like a conventional, digital system, these new devices could potentially function more like a network of neurons.

“Computers are very impressive in many ways, but they’re not equal to the mind,” said Mark Hersam, the Bette and Neison Harris Chair in Teaching Excellence in Northwestern University’s McCormick School of Engineering. “Neurons can achieve very complicated computation with very low power consumption compared to a digital computer.”

A team of Northwestern researchers, including Hersam, has accomplished a new step forward in electronics that could bring brain-like computing closer to reality. The team’s work advances memory resistors, or “memristors,” which are resistors in a circuit that “remember” how much current has flowed through them.

“Memristors could be used as a memory element in an integrated circuit or computer,” Hersam said. “Unlike other memories that exist today in modern electronics, memristors are stable and remember their state even if you lose power.”

Current computers use random access memory (RAM), which moves very quickly as a user works but does not retain unsaved data if power is lost. Flash drives, on the other hand, store information when they are not powered but work much slower. Memristors could provide a memory that is the best of both worlds: fast and reliable. But there’s a problem: memristors are two-terminal electronic devices, which can only control one voltage channel. Hersam wanted to transform it into a three-terminal device, allowing it to be used in more complex electronic circuits and systems.

The memristor is of some interest to a number of other parties prominent amongst them, the University of Michigan’s Professor Wei Lu and HP (Hewlett Packard) Labs, both of whom are mentioned in one of my more recent memristor pieces, a June 26, 2014 post.

Getting back to Northwestern,

Hersam and his team met this challenge by using single-layer molybdenum disulfide (MoS2), an atomically thin, two-dimensional nanomaterial semiconductor. Much like the way fibers are arranged in wood, atoms are arranged in a certain direction–called “grains”–within a material. The sheet of MoS2 that Hersam used has a well-defined grain boundary, which is the interface where two different grains come together.

“Because the atoms are not in the same orientation, there are unsatisfied chemical bonds at that interface,” Hersam explained. “These grain boundaries influence the flow of current, so they can serve as a means of tuning resistance.”

When a large electric field is applied, the grain boundary literally moves, causing a change in resistance. By using MoS2 with this grain boundary defect instead of the typical metal-oxide-metal memristor structure, the team presented a novel three-terminal memristive device that is widely tunable with a gate electrode.

“With a memristor that can be tuned with a third electrode, we have the possibility to realize a function you could not previously achieve,” Hersam said. “A three-terminal memristor has been proposed as a means of realizing brain-like computing. We are now actively exploring this possibility in the laboratory.”

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

Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2 by Vinod K. Sangwan, Deep Jariwala, In Soo Kim, Kan-Sheng Chen, Tobin J. Marks, Lincoln J. Lauhon, & Mark C. Hersam. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.56 Published online 06 April 2015

This paper is behind a paywall but there is a few preview available through ReadCube Access.

Dexter Johnson has written about this latest memristor development in an April 9, 2015 posting on his Nanoclast blog (on the IEEE [Institute for Electrical and Electronics Engineers] website) where he notes this (Note: A link has been removed),

The memristor seems to generate fairly polarized debate, especially here on this website in the comments on stories covering the technology. The controversy seems to fall along the lines that the device that HP Labs’ Stan Williams and Greg Snider developed back in 2008 doesn’t exactly line up with the original theory of the memristor proposed by Leon Chua back in 1971.

It seems the ‘debate’ has evolved from issues about how the memristor is categorized. I wonder if there’s still discussion about whether or not HP Labs is attempting to develop a patent thicket of sorts.

‘Soft’ nanoparticles, 2D liquid, and fluid interfaces

There’s a story about University of Pennsylvania research on 2D liquids and ‘soft’ particles in an April 6, 2015 news item on Azonano,

Researchers at the University of Pennsylvania have used ‘soft’ nanoparticles to create a system that behaves as a 2D liquid. A 2D world exists at the place where oil and water meet. This interface has properties that could be useful for engineers and chemists.

Researchers have been able to make a soap molecule stay at the interface and make it behave in a predictable manner. However, they have not been able to make more complex molecules behave in the same manner.

An April 3, 2015 University of Pennsylvania news release (also on EurekAlert), which appears to have originated the news item, describes the research in detail,

Where water and oil meet, a two-dimensional world exists. This interface presents a potentially useful set of properties for chemists and engineers, but getting anything more complex than a soap molecule to stay there and behave predictably remains a challenge.

A University of Pennsylvania team has now shown how to make nanoparticles that are attracted to this interface but not to each other, creating a system that acts as a two-dimensional liquid. By measuring this liquid’s pressure and density, they have shown a way forward in using it for a variety of applications, such as in nanomanufacturing, catalysis and photonic devices.

By creating a system where these particles do not clump into clusters or skins, they have enabled a way of investigating the physical fundamentals of how nanoscale objects interact with one another in two dimensions.

“Things get stuck at the interface between oil and water,” Stebe said. “That’s of tremendous fundamental and technological interest, because we can think of that interface as a two-dimensional world. If we can start to understand the interactions of the things that accumulate there and learn how they are arranged, we can exploit them in a number of different applications.”

Getting nanoparticles to go to and stay at this interface is tricky, however. Their surface chemistry can easily be adapted to either water or oil, but balancing the two to get the particles to stay in this 2-D regime is more difficult.

“We understand how particles work in 3-D,” Crocker said. “If you put polymer chains on the surface that are attracted to the solvent, the particles will bounce off each other and make a nice suspension, meaning you can do work with them. However, people haven’t really done that in 2-D before.”

Even when particles are able to stay at the interface, they tend to clump together and form a skin that can’t be pulled apart into its constituent particles.

“All particles love themselves,” Stebe said. “Just due to Van der Waals interactions, if they can get close enough, they aggregate. But because our nanoparticles have protective ligand arms, they don’t clump together and form a liquid state. They’re in two-dimensional equilibrium.”

The team’s technique for surmounting this problem hinged on decorating their gold nanoparticles with surfactant, or soap-like, ligands. These ligands have a water-loving head and an oil-loving tail, and the way they are attached to the central particle allows them to contort themselves so both sides are happy when the particle is at an interface. This arrangement produces a “flying saucer” shape, with the ligands stretching out more at the interface than above or below. These ligand bumpers keeps the particles from clumping together.

“This is a very beautiful system,” Stebe said. “The ability to tune their packing means that we can now take everything we know about the equilibrium thermodynamics in two dimensions and start to pose questions about particle layers. Do these particles behave like we think they should? How can we manipulate them in the future?”

To get at the fundamentals of this system, the researchers needed to deduce the relationships of certain properties, such as how the pressure of their 2-D liquid changes as a function of the packing of the particles. They used a variation of the pendant drop method, in which an oil droplet formed in a suspension of particles in water.  Over time, particles attached to the oil-water interface, producing the 2-D liquid in a form where they could measure those traits.

“We can infer the pressure of this 2-D fluid by the shape of the drop,” Stebe said. “Once we compress the drop by pulling some of the oil back into the syringe, we can determine how the shape changes and relate it to the pressure in the layer.”

The researchers also needed to determine how densely the particles were packed. To do so, they wanted to take advantage of the fact that the drop became more opaque as the density of the particle increased when the drop was compressed. However, it was not possible to simply measure the amount of light that shone through the drop, as plasmonic behavior meant that the properties of the gold nanoparticles changed as they got closer together.

“Fortunately, we discovered another interesting feature of this nanoparticle system,” Garbin said. “If the drop was compressed too much, some particles would fall out of the interface because they didn’t fit anymore. This enabled us to measure the amount of particles that were in that falling plume, since the particles are farther apart from each other there. From that measurement, we could work backwards to the number of particles on the interface”

The smooth relationship between the particles’ packing and the pressure of the 2-D liquid they form provides the basis of universal rules that govern the physics of such systems.

”From this data,” Crocker said, “we can figure out the force versus distance of two nanoparticles. That means we can now make a model of how these particles behave in the 2-D liquid.”

Having these rules will allow researchers to develop functional nanoparticles with different traits, such as longer and more complex ligands that perform some chemical task.

“One application is interface catalysis,” Stebe said. “For example, if you have a reagent that’s in the oil phase, but its product is in the water phase, having a particle on the interface that can help move it from one to the other would be perfect.”

A better understanding of when and why particles get trapped in liquid-liquid interfaces could also underpin future work.

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

Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces by Valeria Garbin, Ian Jenkins, Talid Sinno, John C. Crocker, and Kathleen J. Stebe. Phys. Rev. Lett. 114, 108301 (Vol. 114, Iss. 10 — 13 March 2015) Published 9 March 2015 DOI: http://dx.doi.org/10.1103/PhysRevLett.114.108301

This paper is behind a paywall.

A Venus flower basket sea sponge has strength

Despite being made essentially of glass, the skeleton of the sea sponge known as Venus' flower basket is remarkably strong -- right down to the tiny, hair-like fibers that hold the creatures to the sea floor. Researchers from Brown University have shown that those fibers, called spicules, have an intricate internal structure that is fine-tuned to boost strength. The findings could inform the engineering of human-made materials. Credit: Kesari Lab / Brown University

Despite being made essentially of glass, the skeleton of the sea sponge known as Venus’ flower basket is remarkably strong — right down to the tiny, hair-like fibers that hold the creatures to the sea floor. Researchers from Brown University have shown that those fibers, called spicules, have an intricate internal structure that is fine-tuned to boost strength. The findings could inform the engineering of human-made materials.
Credit: Kesari Lab / Brown University

I’m not sure how anyone saw a flower basket in that sponge but I bow to a more poetic soul. In any event, scientists at Brown University (US) have shown that this sponge has unexpected strength according to an April 6, 2015 news item on ScienceDaily,

Life may seem precarious for the sea sponge known as Venus’ flower basket. Tiny, hair-like appendages made essentially of glass are all that hold the creatures to their seafloor homes. But fear not for these creatures of the deep. Those tiny lifelines, called basalia spicules, are fine-tuned for strength, according to new research led by Brown University engineers.

In a paper published in the Proceedings of the National Academy of Sciences, the researchers show that the secret to spicules’ strength lies in their remarkable internal structure. The spicules, each only 50 microns in diameter, are made of a silica (glass) core surrounded by 10 to 50 concentric cylinders of glass, each separated by an ultra-thin layer of an organic material. The walls of each cylinder gradually decrease in thickness moving from the core toward the outside edge of the spicule.

An April 6, 2015 Brown University news release (also on EurekAlert), which originated the news item, describes the research in more detail,

When Haneesh Kesari, assistant professor of engineering at Brown, first saw this structure, he wasn’t sure what to make of it. But the pattern of decreasing thickness caught his eye.

“It was not at all clear to me what this pattern was for, but it looked like a figure from a math book,” Kesari said. “It had such mathematical regularity to it that I thought it had to be for something useful and important to the animal.”

The lives of these sponges depend on their ability to stay fixed to the sea floor. They sustain themselves by filtering nutrients out of the water, which they cannot do if they’re being cast about with the flow. So it would make sense, Kesari thought, that natural selection may have molded the creatures’ spicule anchors into models of strength — and the thickness pattern could be a contributing factor.

“If it can’t anchor, it can’t survive,” Kesari said. “So we thought this internal structure must be contributing to these spicules being a better anchor.”

To find out, Kesari worked with graduate student Michael Monn to build a mathematical model of the spicules’ structure. Among the model’s assumptions was that the organic layers between the glass cylinders allowed the cylinders to slide against each other.

“We prepared a mechanical model of this system and asked the question: Of all possible ways the thicknesses of the layers can vary, how should they vary so that the spicule’s anchoring ability is maximized?” Kesari said.

The model predicted that the structure’s load capacity would be greatest when the layers decrease in thickness toward the outside, just as was initially observed in actual spicules. Kesari and Monn then worked with James Weaver and Joanna Aizenberg of Harvard’s Wyss Institute for Biologically Inspired Engineering, who have worked with this sponge species for years. The team carefully compared the layer thicknesses predicted by the mechanics model to the actual layer thicknesses in more than a hundred spicule samples from sponges.

The work showed that the predictions made by the model matched very closely with the observed layer thicknesses in the samples. “It appears that the arrangement and thicknesses of these layers does indeed contribute to the spicules’ strength, which helps make them better anchors,” Kesari said.

The researchers say this is the first time to their knowledge that anyone has evaluated the mechanical advantage of this particular arrangement of layers. It could add to the list of useful engineered structures inspired by nature.

“In the engineered world, you see all kinds of instances where the external geometry of a structure is modified to enhance its specific strength — I-beams are one example,” Monn said. “But you don’t see a huge effort focused toward the internal mechanical design of these structures.”

This study, however, suggests that sponge spicules could provide a blueprint for load-bearing beams made stronger from the inside out.

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

New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum by Michael A. Monn, James C. Weaver, Tianyang Zhang, Joanna Aizenberg, and Haneesh Kesari. Published online before print April 6, 2015, doi: 10.1073/pnas.1415502112 PNAS April 6, 2015

This paper is behind a paywall.