Tag Archives: Australia

Memristor, memristor, you are popular

Regular readers know I have a long-standing interest in memristor and artificial brains. I have three memristor-related pieces of research,  published in the last month or so, for this post.

First, there’s some research into nano memory at RMIT University, Australia, and the University of California at Santa Barbara (UC Santa Barbara). From a May 12, 2015 news item on ScienceDaily,

RMIT University researchers have mimicked the way the human brain processes information with the development of an electronic long-term memory cell.

Researchers at the MicroNano Research Facility (MNRF) have built the one of the world’s first electronic multi-state memory cell which mirrors the brain’s ability to simultaneously process and store multiple strands of information.

The development brings them closer to imitating key electronic aspects of the human brain — a vital step towards creating a bionic brain — which could help unlock successful treatments for common neurological conditions such as Alzheimer’s and Parkinson’s diseases.

A May 11, 2015 RMIT University news release, which originated the news item, reveals more about the researchers’ excitement and about the research,

“This is the closest we have come to creating a brain-like system with memory that learns and stores analog information and is quick at retrieving this stored information,” Dr Sharath said.

“The human brain is an extremely complex analog computer… its evolution is based on its previous experiences, and up until now this functionality has not been able to be adequately reproduced with digital technology.”

The ability to create highly dense and ultra-fast analog memory cells paves the way for imitating highly sophisticated biological neural networks, he said.

The research builds on RMIT’s previous discovery where ultra-fast nano-scale memories were developed using a functional oxide material in the form of an ultra-thin film – 10,000 times thinner than a human hair.

Dr Hussein Nili, lead author of the study, said: “This new discovery is significant as it allows the multi-state cell to store and process information in the very same way that the brain does.

“Think of an old camera which could only take pictures in black and white. The same analogy applies here, rather than just black and white memories we now have memories in full color with shade, light and texture, it is a major step.”

While these new devices are able to store much more information than conventional digital memories (which store just 0s and 1s), it is their brain-like ability to remember and retain previous information that is exciting.

“We have now introduced controlled faults or defects in the oxide material along with the addition of metallic atoms, which unleashes the full potential of the ‘memristive’ effect – where the memory element’s behaviour is dependent on its past experiences,” Dr Nili said.

Nano-scale memories are precursors to the storage components of the complex artificial intelligence network needed to develop a bionic brain.

Dr Nili said the research had myriad practical applications including the potential for scientists to replicate the human brain outside of the body.

“If you could replicate a brain outside the body, it would minimise ethical issues involved in treating and experimenting on the brain which can lead to better understanding of neurological conditions,” Dr Nili said.

The research, supported by the Australian Research Council, was conducted in collaboration with the University of California Santa Barbara.

Here’s a link to and a citation for this memristive nano device,

Donor-Induced Performance Tuning of Amorphous SrTiO3 Memristive Nanodevices: Multistate Resistive Switching and Mechanical Tunability by  Hussein Nili, Sumeet Walia, Ahmad Esmaielzadeh Kandjani, Rajesh Ramanathan, Philipp Gutruf, Taimur Ahmed, Sivacarendran Balendhran, Vipul Bansal, Dmitri B. Strukov, Omid Kavehei, Madhu Bhaskaran, and Sharath Sriram. Advanced Functional Materials DOI: 10.1002/adfm.201501019 Article first published online: 14 APR 2015

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

This paper is behind a paywall.

The second published piece of memristor-related research comes from a UC Santa Barbara and  Stony Brook University (New York state) team but is being publicized by UC Santa Barbara. From a May 11, 2015 news item on Nanowerk (Note: A link has been removed),

In what marks a significant step forward for artificial intelligence, researchers at UC Santa Barbara have demonstrated the functionality of a simple artificial neural circuit (Nature, “Training and operation of an integrated neuromorphic network based on metal-oxide memristors”). For the first time, a circuit of about 100 artificial synapses was proved to perform a simple version of a typical human task: image classification.

A May 11, 2015 UC Santa Barbara news release (also on EurekAlert)by Sonia Fernandez, which originated the news item, situates this development within the ‘artificial brain’ effort while describing it in more detail (Note: A link has been removed),

“It’s a small, but important step,” said Dmitri Strukov, a professor of electrical and computer engineering. With time and further progress, the circuitry may eventually be expanded and scaled to approach something like the human brain’s, which has 1015 (one quadrillion) synaptic connections.

For all its errors and potential for faultiness, the human brain remains a model of computational power and efficiency for engineers like Strukov and his colleagues, Mirko Prezioso, Farnood Merrikh-Bayat, Brian Hoskins and Gina Adam. That’s because the brain can accomplish certain functions in a fraction of a second what computers would require far more time and energy to perform.

… As you read this, your brain is making countless split-second decisions about the letters and symbols you see, classifying their shapes and relative positions to each other and deriving different levels of meaning through many channels of context, in as little time as it takes you to scan over this print. Change the font, or even the orientation of the letters, and it’s likely you would still be able to read this and derive the same meaning.

In the researchers’ demonstration, the circuit implementing the rudimentary artificial neural network was able to successfully classify three letters (“z”, “v” and “n”) by their images, each letter stylized in different ways or saturated with “noise”. In a process similar to how we humans pick our friends out from a crowd, or find the right key from a ring of similar keys, the simple neural circuitry was able to correctly classify the simple images.

“While the circuit was very small compared to practical networks, it is big enough to prove the concept of practicality,” said Merrikh-Bayat. According to Gina Adam, as interest grows in the technology, so will research momentum.

“And, as more solutions to the technological challenges are proposed the technology will be able to make it to the market sooner,” she said.

Key to this technology is the memristor (a combination of “memory” and “resistor”), an electronic component whose resistance changes depending on the direction of the flow of the electrical charge. Unlike conventional transistors, which rely on the drift and diffusion of electrons and their holes through semiconducting material, memristor operation is based on ionic movement, similar to the way human neural cells generate neural electrical signals.

“The memory state is stored as a specific concentration profile of defects that can be moved back and forth within the memristor,” said Strukov. The ionic memory mechanism brings several advantages over purely electron-based memories, which makes it very attractive for artificial neural network implementation, he added.

“For example, many different configurations of ionic profiles result in a continuum of memory states and hence analog memory functionality,” he said. “Ions are also much heavier than electrons and do not tunnel easily, which permits aggressive scaling of memristors without sacrificing analog properties.”

This is where analog memory trumps digital memory: In order to create the same human brain-type functionality with conventional technology, the resulting device would have to be enormous — loaded with multitudes of transistors that would require far more energy.

“Classical computers will always find an ineluctable limit to efficient brain-like computation in their very architecture,” said lead researcher Prezioso. “This memristor-based technology relies on a completely different way inspired by biological brain to carry on computation.”

To be able to approach functionality of the human brain, however, many more memristors would be required to build more complex neural networks to do the same kinds of things we can do with barely any effort and energy, such as identify different versions of the same thing or infer the presence or identity of an object not based on the object itself but on other things in a scene.

Potential applications already exist for this emerging technology, such as medical imaging, the improvement of navigation systems or even for searches based on images rather than on text. The energy-efficient compact circuitry the researchers are striving to create would also go a long way toward creating the kind of high-performance computers and memory storage devices users will continue to seek long after the proliferation of digital transistors predicted by Moore’s Law becomes too unwieldy for conventional electronics.

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

Training and operation of an integrated neuromorphic network based on metal-oxide memristors by M. Prezioso, F. Merrikh-Bayat, B. D. Hoskins, G. C. Adam, K. K. Likharev,    & D. B. Strukov. Nature 521, 61–64 (07 May 2015) doi:10.1038/nature14441

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

The third and last piece of research, which is from Rice University, hasn’t received any publicity yet, unusual given Rice’s very active communications/media department. Here’s a link to and a citation for their memristor paper,

2D materials: Memristor goes two-dimensional by Jiangtan Yuan & Jun Lou. Nature Nanotechnology 10, 389–390 (2015) doi:10.1038/nnano.2015.94 Published online 07 May 2015

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

Dexter Johnson has written up the RMIT research (his May 14, 2015 post on the Nanoclast blog on the IEEE [Institute of Electrical and Electronics Engineers] website). He linked it to research from Mark Hersam’s team at Northwestern University (my April 10, 2015 posting) on creating a three-terminal memristor enabling its use in complex electronics systems. Dexter strongly hints in his headline that these developments could lead to bionic brains.

For those who’d like more memristor information, this June 26, 2014 posting which brings together some developments at the University of Michigan and information about developments in the industrial sector is my suggestion for a starting point. Also, you may want to check out my material on HP Labs, especially prominent in the story due to the company’s 2008 ‘discovery’ of the memristor, described on a page in my Nanotech Mysteries wiki, and the controversy triggered by the company’s terminology (there’s more about the controversy in my April 7, 2010 interview with Forrest H Bennett III).

Changing the vibration of gold nanodisks (acoustic tuning) with light

A May 7, 2015 news item on phys.org describes research that could have a major impact on photonics applications,

In a study that could open doors for new applications of photonics from molecular sensing to wireless communications, Rice University [Texas, US] scientists have discovered a new method to tune the light-induced vibrations of nanoparticles through slight alterations to the surface to which the particles are attached.

n a study published online this week in Nature Communications, researchers at Rice’s Laboratory for Nanophotonics (LANP) used ultrafast laser pulses to induce the atoms in gold nanodisks to vibrate. These vibrational patterns, known as acoustic phonons, have a characteristic frequency that relates directly to the size of the nanoparticle. The researchers found they could fine-tune the acoustic response of the particle by varying the thickness of the material to which the nanodisks were attached.

A May 7, 2015 Rice University news release (also on EurekAlert), which originated the news item, expands on the theme (Note: A link has been removed),

Our results point toward a straightforward method for tuning the acoustic phonon frequency of a nanostructure in the gigahertz range by controlling the thickness of its adhesion layer,” said lead researcher Stephan Link, associate professor of chemistry and in electrical and computer engineering.

Light has no mass, but each photon that strikes an object imparts a miniscule amount of mechanical motion, thanks to a phenomenon known as radiation pressure. A branch of physics known as optomechanics has developed over the past decade to study and exploit radiation pressure for applications like gravity wave detection and low-temperature generation.

Link and colleagues at LANP specialize in another branch of science called plasmonics that is devoted to the study of light-activated nanostructures. Plasmons are waves of electrons that flow like a fluid across a metallic surface.

When a light pulse of a specific wavelength strikes a metal particle like the puck-shaped gold nanodisks in the LANP experiments, the light energy is converted into plasmons. These plasmons slosh across the surface of the particle with a characteristic frequency, in much the same way that each phonon has a characteristic vibrational frequency.

The study’s first author, Wei-Shun Chang, a postdoctoral researcher in Link’s lab, and graduate students Fangfang Wen and Man-Nung Su conducted a series of experiments that revealed a direct connection between the resonant frequencies of the plasmons and phonons in nanodisks that had been exposed to laser pulses.

“Heating nanostructures with a short light pulse launches acoustic phonons that depend sensitively on the structure’s dimensions,” Link said. “Thanks to advanced lithographic techniques, experimentalists can engineer plasmonic nanostructures with great precision. Based on our results, it appears that plasmonic nanostructures may present an interesting alternative to conventional optomechanical oscillators.”

Chang said plasmonics experts often rely on substrates when using electron-beam lithography to pattern plasmonic structures. For example, gold nanodisks like those used in the experiments will not stick to glass slides. But if a thin substrate of titanium or chromium is added to the glass, the disks will adhere and stay where they are placed.

“The substrate layer affects the mechanical properties of the nanostructure, but many questions remain as to how it does this,” Chang said. “Our experiments explored how the thickness of the substrate impacted properties like adhesion and phononic frequency.”

Link said the research was a collaborative effort involving research groups at Rice and the University of Melbourne in Victoria, Australia.

“Wei-Shun and Man-Nung from my lab did the ultrafast spectroscopy,” Link said. “Fangfang, who is in Naomi Halas’ group here at Rice, made the nanodisks. John Sader at the University of Melbourne, and his postdoc Debadi Chakraborty calculated the acoustic modes, and Yue Zhang, a Rice graduate student from Peter Nordlander’s group at Rice simulated the optical/plasmonic properties. Bo Shuang of the Landes’ research group at Rice contributed to the analysis of the experimental data.”

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

Tuning the acoustic frequency of a gold nanodisk through its adhesion layer by Wei-Shun Chang, Fangfang Wen, Debadi Chakraborty, Man-Nung Su, Yue Zhang, Bo Shuang, Peter Nordlander, John E. Sader, Naomi J. Halas, & Stephan Link. Nature Communications 6, Article number: 7022 doi:10.1038/ncomms8022 Published 05 May 2015

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

Nanotechnology risk perceptions in 2015 from Australia

I haven’t stumbled across a study on the perceptions of risk and nanotechnology in quite a while.  Before commenting on this latest research from the University of Sydney, here’s a link to and a citation for this new Australian study, which is an open access paper,

Perceptions of risk from nanotechnologies and trust in stakeholders: a cross sectional study of public, academic, government and business attitudes by Adam Capon, James Gillespie, Margaret Rolfe, and Wayne Smith. BMC Public Health 2015, 15:424 Published April 26, 2015  DOI: 10.1186/s12889-015-1795-1

According to the authors, this is the first study that surveyed the general public, academics, government officials, and business people with an eye to distinguishing any differences that might exist in their attitudes,

Our study proposes to extend and develop the knowledge base regarding perceptions of risk from nanotechnology and trust by stakeholders. To do this we use a standardised questionnaire across all the stakeholders surveyed. Secondly we examine stakeholder groups beyond highly published scientists and people attending nano conferences/working in nano laboratories that had previously been surveyed to include academic, government and business stakeholders. These three groups were chosen not just for their expertise, but because they represent the interplay of stakeholders most likely to shape policy in this field. Thirdly we seek and report on views of general risk perception (to health) and for specific products (food, cosmetics and sunscreens, medicines, pesticides, tennis racquets and computers) which broadly represent Australian regulatory arms [22]. Finally we explore several trust actors (health department, scientists, journalists and politicians), all of who have the ability to shape policy.

Our study aims to test six hypotheses. First, very little targeted research has been undertaken on differing stakeholder views of risks from nanotechnology. To explore this we hypothesise that public perceptions of risks from nanotechnology will be greater than those held by ‘experts’. Second, existing studies suggest that food and health applications of nanotechnology are likely to arouse more controversy [23]. We will test the hypothesis that the public, academics, government and business respondents will all perceive a higher level of risk in nanotechnologies that penetrate or have close and prolonged contact with the body. Three, there is inconsistent evidence that increased familiarity with nanotechnology is associated with differing perceptions of nanotechnologies [24]. Our third hypothesis proposes that public self-reported familiarity with nanotechnology will be associated with a reduction in risk perception. This relationship will be found with each of the nano products in the study. Four, the public holds less trust in the government agencies with responsibility for regulating nanotechnology than that expressed by people working in nanotechnology based industries/researching nanotechnology [23]. Our fourth hypothesis tests the evidence for this proposition. We hypothesise that the trust the public vests in scientists, the health department, journalists and politicians will be less than those held by business, academic, and government respondents who have an interest in nanotechnology.

The last two hypotheses expand on hypothesis four, examining the trust of the public in greater detail. Studies have shown that the Australian public are more likely to trust scientists and scientific institutions, followed by government agencies with industry and mass media holding the least amount of trust [25],[26]. In our fifth hypothesis we test the proposition that the public will have greatest trust in scientists, followed by the health department with trust in journalists and politicians below these two. Finally, public trust in business leaders [27], science and consumer protection agencies [28] and government agencies [29] have all been associated with decreased nano risk perception. Examining other stakeholders, the greater trust that people working in nanotechnology based industries or researching nanotechnology had with scientists and government agencies, the less they perceived risk from nanotechnology [23],[30]. Our sixth hypothesis is that significant negative associations exist between the trust the public vest in scientists, health department, journalists and politicians and perceived risk of nanotechnology, both when this risk is considered to health and across all risk applications. Understanding this relationship between trust and risk perception is an important avenue for risk communication and education.

As interesting as I find methodology I’m going to skip most of it and focus on the sample size and demographics,

The surveys consisted of 1355 public, 301 academic, 19 government and 21 business responses. Gender representation of the weighted public survey population was comparable to the June 2012 Australian population estimates of approximately 50% male and female. Gender representationa for academic and business responses was more likely to be male (≈70%) while the gender of government respondents was almost evenly balanced.

Three hundred and ninety eight public respondents (30%) were categorised as having no familiarity with nanotechnology, while 528 (39%) were categorised as having some familiarity and 422 (31%) as having moderate familiarity with nanotechnology.

Amongst the academic responses, the best represented area of research (38%) was in the field of nanomaterials. Nanocharacterisation, nanofabrication, nanobiotechnology/nanomedicine, nanoscale theory/computation, nanophotonics, and nanoelectronics/nanomagnetics represented between 15% to 4% per discipline in descending order. The least represented discipline was translational nanoresearch (2%), of which half were involved in nanotoxicology and the other either in ethical or social research on risk/public attitudes/public impact or did not provide a sub specialisation. Of the business responses the greatest percentage of business involvement was in nanomaterial manufacture, importation or research (33% – 23%). Importation of products containing nanomaterials, waste collection/processing and legal issues had little representation. The highest representation of government respondents was health and safety (37%) followed by communication/social impact (26%), business development (16%) and environment (11%).

The analysis of the results is well worth reading,

The Australian public perceives greater risks from manufactured nanomaterials and shows less trust in scientists and the health department to provide protection from possible health effects than academic, business and government stakeholders in the nanotechnology sector. Food applications and cosmetics/sunscreens loom high on the list of public concerns, although medicines and pesticides are also causes of public concern. Policy makers should be aware of these risk and trust disparities and address public sentiment by treating nanotechnology applications in the higher risk areas with greater caution. Risk communication is best placed in the hands of trusted scientists.

I am a little surprised that no mention was made of the nanosunscreen situation of 2012 where a research study found that 13% (originally reported as 17%) of Australians surveyed said they didn’t use any sunscreens due to fear of nanoparticles. I have the story in my Feb. 9, 2012 posting. Be sure to read through to the end as there were a couple of updates.

Gold detection down to the nanoparticle?

It appears that detecting gold, presumably for mining purposes, isn’t as easy as one might think especially at the nanoscale. Researchers at Australia’s University of Adelaide have devised a new method according to an April 29, 2015 news item on Nanowerk (Note: A link has been removed),

University of Adelaide researchers are developing a portable, highly sensitive method for gold detection that would allow mineral exploration companies to test for gold on-site at the drilling rig.

Using light in two different processes (fluorescence and absorption), the researchers from the University’s Institute for Photonics and Advanced Sensing (IPAS), have been able to detect gold nanoparticles at detection limits 100 times lower than achievable under current methods.

An April 29, 2015 University of Adelaide news release details Australia’s interest in gold and offers a high level explanation of the need for better gold detection (Note: Links have been removed),

Australia is the world’s second largest gold producer, worth $13 billion in export earnings.

“Gold is not just used for jewellery, it is in high demand for electronics and medical applications around the world, but exploration for gold is extremely challenging with a desire to detect very low concentrations of gold in host rocks,” says postdoctoral researcher Dr Agnieszka Zuber, working on the project with Associate Professor Heike Ebendorff-Heidepriem.

“The presence of gold deep underground is estimated by analysis of rock particles coming out of the drilling holes. But current portable methods for detection are not sensitive enough, and the more sensitive methods require some weeks before results are available.

“This easy-to-use sensor will allow fast detection right at the drill rig with the amount of gold determined within an hour, at much lower cost.”

The researchers have been able to detect less than 100 parts per billion of gold in water. They are now testing using samples of real rock with initial promising results. The work is funded by the Deep Exploration Technologies Cooperative Research Centre.

The gold detection project is one of a series of projects which will be presented at the IPAS Minerals and Energy Sector Workshop today [April 29, 2015], aimed at linking resources specific research to local companies.

You can find out more about the University of Adelaide’s Institute of Photonics and Advanced Sensing here.

Building architecture inspires new light-bending material

Usually, it’s nature which inspires scientists but not this time. Instead, a building in Canberra, Australia has provided the inspiration according to a March 24, 2015 news item on Nanowerk,

Physicists inspired by the radical shape of a Canberra building have created a new type of material which enables scientists to put a perfect bend in light.

The creation of a so-called topological insulator could transform the telecommunications industry’s drive to build an improved computer chip using light.

Leader of the team, Professor Yuri Kivshar from The Australian National University (ANU) said the revolutionary material might also be useful in microscopes, antenna design, and even quantum computers.

“There has been a hunt for similar materials in photonics based on large complicated structures,” said Professor Kivshar, who is the head of the Nonlinear Physics Centre in ANU Research School of Physics and Engineering.

“Instead we used a simple, small-scale zigzag structure to create a prototype of these novel materials with amazing properties.”

The structure was inspired by the Nishi building near ANU, which consists of rows of offset zigzag walls.

Here’s what the building looks like,

Caption: Alex Slobozhanyuk (L) and Andrey Miroshnichenko with models of their material structures in front of the Nishi building that inspired them. Credit: Stuart Hay, ANU

Caption: Alex Slobozhanyuk (L) and Andrey Miroshnichenko with models of their material structures in front of the Nishi building that inspired them.
Credit: Stuart Hay, ANU

A March 24, 2015 Australian National University press release, which originated the news item, goes on to describe topological insulators and what makes this ‘zigzag’ approach so exciting,

Topological insulators have been initially developed for electronics, and the possibility of building an optical counterpart is attracting a lot of attention.

The original zigzag structure of the material was suggested in the team’s earlier collaboration with Dr Alexander Poddubny, from Ioffe Institute in Russia, said PhD student Alexey Slobozhanyuk.

“The zigzag structure creates a coupling throughout the material that prevents light from travelling through its centre,” Mr Slobozhanyuk said.

“Instead light is channelled to the edges of the material, where it becomes completely localised by means of a kind of quantum entanglement known as topological order.”

Fellow researcher Dr Andrew Miroshnichenko said the building inspired the researchers to think of multiple zigzags.

“We had been searching for a new topology and one day I looked at the building and a bell went off in my brain,” said fellow researcher Dr Andrey Miroshnichenko.

“On the edges of such a material the light should travel completely unhindered, surfing around irregularities that would normally scatter the light.

“These materials will allow light to be bent around corners with no loss of signal,” he said.

The team showed that the exceptional attributes of the material are related to its structure, or topology, and not to the molecules it is made from.

“In our experiment we used an array of ceramic spheres, although the initial theoretical model used metallic subwavelength particles,” said Dr Miroshnichenko.

“Even though they are very different materials they gave the same result.”

In contrast with other international groups attempting to create topological insulators with large scale structures, the team used spheres that were smaller than the wavelength of the microwaves in their successful experiments.

Dr Poddubny devised the theory when he realised there was a direct analogy between quantum Kitaev’s model of Majorana fermions and optically coupled subwavelength scatterers.

Mr Slobozhanyuk said the team could control which parts of the material surface the light is channelled to by changing the polarisation of the light.

“This opens possibilities ranging from nanoscale light sources for enhancing microscopes, highly efficient antennas or even quantum computing,” he said.

“The structure couples the two sides of the material, so they could be used as entangled qubits for quantum computing.”

It would be nice to offer a link to a published paper but I cannot find one.

Looking for nano silicon at 10 nm (nanometres)

I received this request from Greg Packer on March 17, 2015,

Dear Sir we are looking for suppliers of a small qty say 5 kilo of nano silicon 10nm for hydrogen production with water for testing of a new producť designed fòr Ìndia.If you can help please ĺet us know plus the cost we are on the Gold Coast Qld
Thanks Greg Packer. 0403159635

As the request was in a comment to a post from 2010 I’m not sure how many people would see it and so have placed it here. The Gold Coast he is referring to is in Queensland, Australia.

To be clear, I do not know Mr. Packer and am not familiar with the product or his company but if you’re selling, it never hurts to check these things out.

How geckos self-clean, even in dusty environments

An Australian research team claims a world first with regard to ‘gecko research’ according to a March 16, 2014 news item on ScienceDaily,

In a world first, a research team including James Cook University [JCU] scientists has discovered how geckos manage to stay clean, even in dusty deserts.

The process, described in Interface, a journal of the Royal Society, may also turn out to have important human applications.

JCU’s Professor Lin Schwarzkopf said the group found that tiny droplets of water on geckos, for instance from condensing dew, come into contact with hundreds of thousands of extremely small hair-like spines that cover the animals’ bodies.

A March 16, 2015 JCU press release (also on EurekAlert), which originated the news item, provides more detail,

“If you have seen how drops of water roll off a car after it is waxed, or off a couch that’s had protective spray used on it, you’ve seen the process happening,” she said. “The wax and spray make the surface very bumpy at micro and nano levels, and the water droplets remain as little balls, which roll easily and come off with gravity or even a slight wind.”

The geckos’ hair-like spines trap pockets of air and work on the same principle, but have an even more dramatic effect. Through a scanning electron microscope, tiny water droplets can be seen rolling into each other and jumping like popcorn off the skin of the animal as they merge and release energy.

Scientists were aware that hydrophobic surfaces repelled water, and that the rolling droplets helped clean the surfaces of leaves and insects, but this is the first time it has been documented in a vertebrate animal. Box-patterned geckos live in semi-arid habitats, with little rain but may have dew forming on them when the temperature drops overnight.

Professor Schwarzkopf said the process may help geckos keep clean, as the water can carry small particles of dust and dirt away from their body. “They tend to live in dry environments where they can’t depend on it raining, and this keeps process them clean,” she said.

She said there were possible applications for marine-based electronics that have to shed water quickly in use and for possible “superhydrophobic” clothing that would not get wet or dirty and would never need washing.

I’ve been reading about self-cleaning products for years now. (sigh) Where are they? Despite this momentary lapse into sighing and wailing, I am much encouraged that scientists are still trying to figure out how to create self-cleaning products.

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

Removal mechanisms of dew via self-propulsion off the gecko skin by Gregory S. Watson, Lin Schwarzkopf, Bronwen W. Cribb, Sverre Myhra, Marty Gellender, and Jolanta A. Watson.
Interface, April 2015, Volume: 12 Issue: 105 DOI: 10.1098/rsif.2014.1396 Published 11 March 2015

This paper is open access.

Optical nanoantennas open up lab-on-a-chip possibilities

A Feb. 24, 2015 news item on Nanowerk describes nanoantenna research coming out of Australia (Note: A link has been removed),

Newly developed tiny antennas, likened to spotlights on the nanoscale, offer the potential to measure food safety, identify pollutants in the air and even quickly diagnose and treat cancer, according to the Australian scientists who created them. The new antennas are cubic in shape. They do a better job than previous spherical ones at directing an ultra-narrow beam of light where it is needed, with little or no loss due to heating and scattering, they say.

In a paper published in the Journal of Applied Physics (“Optically resonant magneto-electric cubic nanoantennas for ultra-directional light scattering”), Debabrata Sikdar of Monash University in Victoria, Australia, and colleagues describe these and other envisioned applications for their nanocubes in “laboratories-on-a-chip.” …

A Feb. 24, 2015 American Institute of Physics news release on EurekAlert, which originated the news item, describes the work in detail,

… The cubes, composed of insulating, rather than conducting or semiconducting materials as were the spherical versions, are easier to fabricate as well as more effective, he [Sikdar] says.

Sikdar’s paper presents analysis and simulation of 200-nanometer dielectric (nonconductive) nanoncubes placed in the path of visible and near-infrared light sources. The nanocubes are arranged in a chain, and the space between them can be adjusted to fine-tune the light beam as needed for various applications. As the separation between cubes increases, the angular width of the beam narrows and directionality improves, the researchers say.

“Unidirectional nanoantennas induce directionality to any omnidirectional light emitters like microlasers, nanolasers or spasers, and even quantum dots,” Sikdar said in an interview. Spasers are similar to lasers, but employ minute oscillations of electrons rather than light. Quantum dots are tiny crystals that produce specific colors, based on their size, and are widely used in color televisions. “Analogous to nanoscale spotlights, the cubic antennas focus light with precise control over direction and beam width,” he said. [emphasis mine]

The new cubic nanoantennas have the potential to revolutionize the infant field of nano-electromechanical systems (NEMS). “These unidirectional nanoantennas are most suitable for integrated optics-based biosensors to detect proteins, DNA, antibodies, enzymes, etc., in truly portable lab-on-a-chip platforms of the future,” Sikdar said. “They can also potentially replace the lossy on-chip IC (integrated circuit) interconnects, via transmitting optical signals within and among ICs, to ensure ultrafast data processing while minimizing device heating,” he added. [emphasis mine]

Sikdar and his colleagues plan to begin constructing unidirectional cubic NEMS antennas in the near future at the Melbourne Center for Nanofabrication. “We would like to collaborate with other research groups across the world, making all these wonders possible,” he said.

I’m glad the writer included Sikdar’s explanation of spasers and quantum dots and thank them both for a new word, “lossy.” Here’s a link to and a citation for the paper,

Optically resonant magneto-electric cubic nanoantennas for ultra-directional light scattering by Debabrata Sikdar, Wenlong Cheng, and Malin Premaratne. J. Appl. Phys. 117, 083101 (2015); http://dx.doi.org/10.1063/1.4907536

This article is open access.

Microplasm-generated gold nanoparticles and the heart

Scientists are hoping they’ve found a better way to detect early signs of a heart attack according to a Jan. 15, 2015 news item on Nanotechnology Now,

NYU [New York University] Polytechnic School of Engineering professors have been collaborating with researchers from Peking University on a new test strip that is demonstrating great potential for the early detection of certain heart attacks.

Kurt H. Becker, a professor in the Department of Applied Physics and the Department of Mechanical and Aerospace Engineering, and WeiDong Zhu, a research associate professor in the Department of Mechanical and Aerospace Engineering, are helping develop a new colloidal gold test strip for cardiac troponin I (cTn-I) detection. The new strip uses microplasma-generated gold nanoparticles (AuNPs) and shows much higher detection sensitivity than conventional test strips. The new cTn-I test is based on the specific immune-chemical reactions between antigen and antibody on immunochromatographic test strips using AuNPs.

A Jan. 14, 2015 NYU Polytechnic School of Engineering news release (also on EurekAlert but dated Jan. 15, 2015), which originated the news item, explains what makes these new test strips more sensitive (hint: microplasma-generated gold nanoparticles),

Compared to AuNPs produced by traditional chemical methods, the surfaces of the gold nanoparticles generated by the microplasma-induced liquid chemical process attract more antibodies, which results in significantly higher detection sensitivity.

cTn-I is a specific marker for myocardial infarction. The cTn-I level in patients experiencing cardiac infarction is several thousand times higher than in healthy people. The early detection of cTn-I is therefore a key factor of heart attack diagnosis and therapy.

The use of microplasmas to generate AuNP is yet another application of the microplasma technology developed by Becker and Zhu.  Microplasmas have been used successfully in dental applications (improved bonding, tooth whitening, root canal disinfection), biological decontamination (inactivation of microorganisms and biofilms), and disinfection and preservation of fresh fruits and vegetables.

The microplasma-assisted synthesis of AuNPs has great potential for other biomedical and therapeutic applications such as tumor detection, cancer imaging, drug delivery, and treatment of degenerative diseases such as Alzheimer’s.

The routine use of gold nanoparticles in therapy and disease detection in patients is still years away: longer for therapeutic applications and shorter for biosensors. The biggest hurdle to overcome is the fact that the synthesis of monodisperse, size-controlled gold nanoparticles, even using microplasmas, is still a costly, time-consuming, and labor-intensive process, which limits their use currently to small-scale clinical studies, Becker explained.

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

Microplasma-Assisted Synthesis of Colloidal Gold Nanoparticles and Their Use in the Detection of Cardiac Troponin I (cTn-I) by Ruixue Wang, Shasha Zuo, Dong Wu, Jue Zhang, Weidong Zhu, Kurt H. Becker, and Jing Fang. Plasma Processes and Polymers DOI: 10.1002/ppap.201400127 Article first published online: 11 DEC 2014

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

This article is behind a paywall.

For anyone curious about the more common chemical methods of producing gold nanoparticles, there’s this video produced in Australia by TechNyou Education. There’s a specific technique described which I believe is one of the most commonly used and I think this can be generalized to other gold nanoparticle chemical production processes,

One more thing, this video runs over my 5 min. policy limit for videos. To do this, I battled my inclination to include something that I think is useful for understanding more about nanoparticles and my desire to make sure that my blog doesn’t get too bloated.

Gold nanorod instabilities

A Dec. 8, 2014 news item on Nanowerk focuses on research from Australia,

Researchers at Swinburne University of Technology [Melbourne, Australia]  have discovered an instability in gold nanoparticles that is critical for their application in future technology.

Gold nanorods are important building blocks for future applications in solar cells, cancer therapy and optical circuitry.

However their stability is under question due to their peculiar reshaping behaviour below melting points.

A Dec. 8, 2014 Swinburne University of Technology press release, which originated the news item, discusses melting points and shape instabilities in the context of this research,

A solid normally does not change its shape unless it reaches its melting point, or surface melting points. It is also known that the melting point for nanoparticles is suppressed due to their size.

PhD student Adam Taylor (now a postdoctoral researcher at Swinburne) said it came as a surprise that reshaping is observed well below these melting points. Until now, no one could explain this peculiar behaviour.

“In our work, we have discovered both theoretically and experimentally that the reshaping mechanism for nanoparticles below melting point is surface atom diffusion, rather than melting,” Mr Taylor said.

Surface atom diffusion is a process involving the motion of molecules at solid material surfaces that can generally be thought of in terms of particles jumping between adjacent adsorption sites on a surface.

“Surface atom diffusion always existed in bulk solids, but this is the first evidence that its effect is enhanced at the nano-size, dominating over the traditional theory of melting,” Associate Professor James Chon, who is supervising Mr Taylor’s research, said.

Mr Taylor said the more finely nanoparticles are shaped, the less stable they become.

“This is important, for example, for solar panel manufacturers as the more needle-like these nanoparticles are shaped the less stable they become. If you put these particles into a solar panel to concentrate light they may not last long in the sun before they degrade,” Mr Taylor said.

“This discovery will be crucial for future applications of gold nanorods, as people will need to reconsider their stability when applying them to solar cells, cancer therapeutic agents and optical circuitry.”

The researchers have provided an illustration of their work,

Courtesy Swinburne University of Technology

Courtesy Swinburne University of Technology

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

Below Melting Point Photothermal Reshaping of Single Gold Nanorods Driven by Surface Diffusion by Adam B. Taylor, Arif M. Siddiquee, and James W. M. Chon. ACS Nano, Article ASAP DOI: 10.1021/nn5055283 Publication Date (Web): November 18, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall but should you be in Australia and eligible to attend, there’s another opportunity to learn more; Taylor will be presenting his work at the Australian Institute of Physics conference on December 10, 2014 in Canberra.