Category Archives: nanotechnology

Acoustics and carbon nanotubes

Mikhail Koslov from the University of Texas at Dallas has written a Dec. 18, 2014 Nanowerk Spotlight article about his research into carbon nanotubes and their acoustic properties,

Carbon nanotube assemblies enabled design of a hybrid thermo-electromagnetic sound transducer with unique sound generation features that are not available from conventional diaphragm and thermo-acoustic speakers.

EM image of multi-walled carbon nanotube sheet used for thermo-electromagnetic sound transducer. (Image: Mikhail Kozlov, University of Texas at Dallas)

EM image of multi-walled carbon nanotube sheet used for thermo-electromagnetic sound transducer. (Image: Mikhail Kozlov, University of Texas at Dallas)

Kozlov goes on to explain his work in more detail,

… a hybrid thermo-electromagnetic sound transducer (TEMST) [was] fabricated using highly porous multi-walled carbon nanotube sheet that was placed in the proximity of a permanent magnet. Upon electrical AC excitation, thermal response of the material is combined with diaphragm-like sheet oscillations induced by the electromagnetic action of the Lorentz force.

Unlike conventional diaphragm loudspeaker, acoustic spectrum of the TEMST device consists of a superposition of TA and EM responses that can be altered by applied bias voltage. Variation of bias voltage changes spectral intensity and spatial distribution of generated sound.

In particular, propagation direction of the sound can be reversed by switching bias polarity that somewhat resembles voltage-controlled acoustic reflection. Such uncommon behavior was explained by interference of the two contributions being beneficial for diverse sound management applications.

It was found also that amplitude of first TEMST harmonic changes a lot with applied magnetic field, while the second one remains almost field independent. This unusual feature is convenient for magnetic sensing similar to that enabled by Lorentz force magnetometers. The magnetic field detection in the TEMST device is facilitated by the audio sensing system.

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

Thermo-electromagnetic sound transducer based on carbon nanotube sheet by Mikhail Kozlov and Jiyoung Oh. J. Appl. Phys. 116, 094301 (2014); http://dx.doi.org/10.1063/1.4894143 Published online Sept. 2, 2014

This paper is behind a paywall.

Quantum dots cycling through the food chain

Rice University (Texas, US) researchers have published a study which follows quantum dot nanoparticles as they enter the water supply and are taken up by plant roots and leaves and eaten by caterpillars. From a Dec. 16, 2014 news item on ScienceDaily,

In one of the most comprehensive laboratory studies of its kind, Rice University scientists traced the uptake and accumulation of quantum dot nanoparticles from water to plant roots, plant leaves and leaf-eating caterpillars.

The study, one of the first to examine how nanoparticles move through human-relevant food chains, found that nanoparticle accumulation in both plants and animals varied significantly depending upon the type of surface coating applied to the particles. The research is available online in the American Chemical Society’s journal Environmental Science & Technology.

A Dec. 16, 2014 Rice University news release (also on EurekAlert), which originated the news item, provides insight into some of the issues being addressed with this research (Note: Links have been removed),

“With industrial use of nanoparticles on the rise, there are increasing questions about how they move through the environment and whether they may accumulate in high levels in plants and animals that people eat,” said study co-author Janet Braam, professor and chair of the Department of BioSciences at Rice.

Braam and colleagues studied the uptake of fluorescent quantum dots by Arabidopsis thaliana, an oft-studied plant species that is a relative of mustard, broccoli and kale. In particular, the team looked at how various surface coatings affected how quantum dots moved from roots to leaves as well as how the particles accumulated in leaves. The team also studied how quantum dots behaved when caterpillars called cabbage loopers (Trichoplusia ni) fed upon plant leaves containing quantum dots.

“The impact of nanoparticle uptake on plants themselves and on the herbivores that feed upon them is an open question,” said study first author Yeonjong Koo, a postdoctoral research associate in Braam’s lab. “Very little work has been done in this area, especially in terrestrial plants, which are the cornerstone of human food webs.”

Some toxins, like mercury and DDT, tend to accumulate in higher concentrations as they move up the food chain from plants to animals. It is unknown whether nanoparticles may also be subject to this process, known as biomagnification.

While there are hundreds of types of nanoparticles in use, Koo chose to study quantum dots, submicroscopic bits of semiconductors that glow brightly under ultraviolet light. The fluorescent particles — which contained cadmium, selenium, zinc and sulfur — could easily be measured and imaged in the tests. In addition, the team treated the surface of the quantum dots with three different polymer coatings — one positively charged, one negatively charged and one neutral.

“In industrial applications, nanoparticles are often coated with a polymer to increase solubility, improve stability, enhance properties and for other reasons,” said study co-author Pedro Alvarez, professor and chair of Rice’s Department of Civil and Environmental Engineering. “We expect surface coatings to play a significant role in whether and how nanomaterials may accumulate in food webs.”

Previous lab studies had suggested that the neutral coatings might cause the nanoparticles to aggregate and form clumps that were so large that they would not readily move from a plant’s roots to its leaves. The experiments bore this out. Of the three particle types, only those with charged coatings moved readily through the plants, and only the negatively charged particles avoided clumping altogether. The study also found that the type of coating impacted the plants’ ability to biodegrade, or break down, the quantum dots.

Koo and colleagues found caterpillars that fed on plants containing quantum dots gained less weight and grew more slowly than caterpillars that fed on untainted leaves. By examining the caterpillar’s excrement, the scientists were also able to estimate whether cadmium, selenium and intact quantum dots might be accumulating in the animals. Again, the coating played an important role.

“Our tests were not specifically designed to measure bioaccumulation in caterpillars, but the data we collected suggest that particles with positively charged coatings may accumulate in cells and pose a risk of bioaccumulation,” Koo said. “Based on our findings, more tests should be conducted to determine the extent of this risk under a broader set of ecological conditions.”

The researchers have a couple of images illustrating their work,

The buildup of fluorescent quantum dots in the leaves of Arabidopsis plants is apparent in this photograph of the plants under ultraviolet light. Credit: Y. Koo/Rice University

The buildup of fluorescent quantum dots in the leaves of Arabidopsis plants is apparent in this photograph of the plants under ultraviolet light. Credit: Y. Koo/Rice University

And, there’s a caterpillar,

Cabbage looper

Cabbage looper

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

Fluorescence Reports Intact Quantum Dot Uptake into Roots and Translocation to Leaves of Arabidopsis thaliana and Subsequent Ingestion by Insect Herbivores by Yeonjong Koo, Jing Wang, Qingbo Zhang, Huiguang Zhu, E. Wassim Chehab, Vicki L. Colvin, Pedro J. J. Alvarez, and Janet Braam. Environ. Sci. Technol., Just Accepted Manuscript DOI: 10.1021/es5050562 Publication Date (Web): December 1, 2014

Copyright © 2014 American Chemical Society

This paper is open access but you must be registered on the website.

One final thought about the research, it did take place in a laboratory environment and there doesn’t seem to have been any soil involved so the uptake can not be directly compared (as I understand matters) to the uptake characteristics where plant cultivation requires soil. This seems to have been a study involving hydroponic framing practices.

Gold nanoparticles as catalysts for clear water and hydrogen production

The research was published online May 2014 and in a July 2014 print version,  which seems a long time ago now but there’s a renewed interest in attracting attention for this work. A Dec. 17, 2014 news item on phys.org describes this proposed water purification technology from Singapore’s A*STAR (Agency for Science Technology and Research), Note: Links have been removed,

A new catalyst could have dramatic environmental benefits if it can live up to its potential, suggests research from Singapore. A*STAR researchers have produced a catalyst with gold-nanoparticle antennas that can improve water quality in daylight and also generate hydrogen as a green energy source.

This water purification technology was developed by He-Kuan Luo, Andy Hor and colleagues from the A*STAR Institute of Materials Research and Engineering (IMRE). “Any innovative and benign technology that can remove or destroy organic pollutants from water under ambient conditions is highly welcome,” explains Hor, who is executive director of the IMRE and also affiliated with the National University of Singapore.

A Dec. 17, 2014 A*STAR research highlight, which originated the news item, describes the photocatalytic process the research team developed and tested,

Photocatalytic materials harness sunlight to create electrical charges, which provide the energy needed to drive chemical reactions in molecules attached to the catalyst’s surface. In addition to decomposing harmful molecules in water, photocatalysts are used to split water into its components of oxygen and hydrogen; hydrogen can then be employed as a green energy source.

Hor and his team set out to improve an existing catalyst. Oxygen-based compounds such as strontium titanate (SrTiO3) look promising, as they are robust and stable materials and are suitable for use in water. One of the team’s innovations was to enhance its catalytic activity by adding small quantities of the metal lanthanum, which provides additional usable electrical charges.

Catalysts also need to capture a sufficient amount of sunlight to catalyze chemical reactions. So to enable the photocatalyst to harvest more light, the scientists attached gold nanoparticles to the lanthanum-doped SrTiO3 microspheres (see image). These gold nanoparticles are enriched with electrons and hence act as antennas, concentrating light to accelerate the catalytic reaction.

The porous structure of the microspheres results in a large surface area, as it provides more binding space for organic molecules to dock to. A single gram of the material has a surface area of about 100 square meters. “The large surface area plays a critical role in achieving a good photocatalytic activity,” comments Luo.

To demonstrate the efficiency of these catalysts, the researchers studied how they decomposed the dye rhodamine B in water. Within four hours of exposure to visible light 92 per cent of the dye was gone, which is much faster than conventional catalysts that lack gold nanoparticles.

These microparticles can also be used for water splitting, says Luo. The team showed that the microparticles with gold nanoparticles performed better in water-splitting experiments than those without, further highlighting the versatility and effectiveness of these microspheres.

The researchers have provided an illustration of the process,

Improved photocatalyst microparticles containing gold nanoparticles can be used to purify water. © 2014 A*STAR Institute of Materials Research and Engineering

Improved photocatalyst microparticles containing gold nanoparticles can be used to purify water.
© 2014 A*STAR Institute of Materials Research and Engineering

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

Novel Au/La-SrTiO3 microspheres: Superimposed Effect of Gold Nanoparticles and Lanthanum Doping in Photocatalysis by Guannan Wang, Pei Wang, Dr. He-Kuan Luo, and Prof. T. S. Andy Hor. Chemistry – An Asian Journal Volume 9, Issue 7, pages 1854–1859, July 2014. Article first published online: 9 MAY 2014 DOI: 10.1002/asia.201402007

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

This article is behind a paywall.

Self-healing (high voltage installations) in the subsea and a search for funding

More concept than reality, nonetheless, the possibilities offered by this Scandinavian research are appealing. From a Dec. 16, 2014 news item on ScienceDaily,

Embryonic faults in subsea high voltage installations are difficult to detect and very expensive to repair. Researchers believe that self-repairing materials could be the answer.

The vital insulating material which encloses sensitive high voltage equipment may now be getting some ‘first aid’.

“We have preliminary results indicating that this is a promising concept, but we need to do more research to check out other solutions and try the technique out under different conditions.” So says SINTEF [largest independent research organisation in Scandinavial researcher Cédric Lesaint, who is hoping that the industry will soon wake up to the idea.

A Nov. 26, 2014 SINTEF press release, which originated the news item, describes the concept in more detail,

The technology used involves so-called ‘microcapsules’, which are added to traditional insulation materials and have the ability to ‘sniff out’ material fatigue and then release repairing molecules. The team working on this project is made up of chemists, physicists and electrical engineers. If they succeed, they may have discovered the next generation of insulating materials which can be applied in costly electrical installations.

The press release then describes a phenomenon named ‘electrical trees’,

So-called electrical trees develop in electrical insulation materials that are approaching the end of their useful lives. Electrical stress fields exploit small weaknesses in the insulation material and generate hair-thin channels that spread through the material like the branches of a tree. When the channels finally reach the surface of the insulation material, the damage is done and short-circuiting will occur.

“Short-circuiting is almost always linked to an electrical tree”, explains Lesaint’s colleague, Øystein Hestad.

Faults of this kind are extremely expensive to repair, especially if they occur in a device installed on an offshore wind farm or a subsea oil production installation – perhaps even under inhospitable Arctic conditions.

Under such conditions, say researchers, self-repairing insulation materials represent a cost-effective alternative to traditional repair methods.

The specific solution the researchers propose (from the press release),

SINTEF researchers have based their work on an established idea developed to repair mechanical damage and cracks in composite materials. The composites are mixed with microcapsules filled with a liquid monomer – single molecules which have the property to join with each other (polymerise) to form long-chain molecules. If cracks or other forms of damage encroach on the capsules, the monomer is released and fills the cracks.

“As far as we know, we’re the first to have tested this technique on damage resulting from electrical stress fields”, says Lesaint.

The microcapsules they incorporated into the insulation materials burst when they encounter one of the branches of an electrical tree. The liquid monomer then invades the thin channels forming the ‘tree’ and polymerises. The channels are filled in and the electrical degradation of the insulation material is halted.

In this way the ‘immune defences’ of the insulation material are strengthened, and the lifetime of the installation extended.

As promising as the research is, the scientists are looking for funds (from the press release),

This summer [2014], the SINTEF research team presented the concept at a conference in Philadelphia, USA.

“Many people were surprised, especially when they realised that we had chosen to share the concept with others”, says Lesaint. “Taking the chance that other researchers might steal such a good idea is a risk we have to take”, he says.

The industry has also expressed some interest, but so far not enough to consider funding further research.

“We’re being met with curious interest, but have been told to come back when we have more test results”, says Lesaint. “The problem is that at present we have insufficient funds to conduct the research needed to carry the project forward”, he says.

Next year [2015?] will thus decide as to whether this self-repairing project will take the step from being a promising concept to becoming the next generation of insulation materials.

You can also find the press release/article by Lars Martin Hjortho here in  a Gemini.no newsletter.

Here’s an illustration the researchers have made available,

Subsea installations can get longer life-time with self-repairing materials. Illustration: SINTEF Energy  [downloaded from http://gemini.no/en/2014/11/self-repairing-subsea-material/]

Subsea installations can get longer life-time with self-repairing materials. Illustration: SINTEF Energy [downloaded from http://gemini.no/en/2014/11/self-repairing-subsea-material/]

Insurance companies, the future, and perceptions about nanotechnology risks

Michael Berger has written a Dec. 15, 2014 Nanowerk Spotlight about a study examining perceptions of nanotechnology risks amongst members of the insurance industry,

Insurance companies are major stakeholders capable of contributing to the safer and more sustainable development of nanotechnologies and nanomaterials. This is owed to the fact that the insurance industry is one of the bearers of potential losses that can arise from the production and use of nanomaterials and nanotechnology applications.

Researchers at the University of Limerick in Ireland have examined how the insurance market perception of nanotechnology can influence the sustainability of technological advances and insurers’ concern for nanotechnology risks. They claim that, despite its role in sustaining technology development in modern society, insurers’ perception on nanomaterials has been largely overlooked by researchers and regulators alike.

I encourage you to read Berger’s piece in its entirety as it includes nuggets such as this,

… Over 64 per cent of surveyed insurers said they were vaguely familiar with nanotechnology and nanomaterial terms, and over 25 per cent said they had a moderate working knowledge and were able to define the terms. The interview data, however, suggests that this knowledge is at a basic level and there is a need for more information in order to allow this group to differentiate between distinct nanomaterial risks.

For those of you who would like to read the researchers’ paper in its entirety, you can find it in the Geneva Association Newsletter: Risk Management, No. 54, June 2014 where you will find a very interesting set of prognostications in Walter R. Stahel’s editorial,

In the editorial of the Risk Management newsletter of May 2013, I was looking back at 25 years of Risk Management Research of The Geneva Association. Today, this editorial and newsletter will look at some specific risks of the next 25 years.

If we first look back 25 years, to 1988, the PC had just been invented, Internet was still an internal network at the site of its invention the CERN [European Particle Physics Laboratory] in Geneva, cars were driven by people and mobile phones weighed five kilos and cost $5000, to give but a few technical examples. Dying forests, air pollution and retreating glaciers were the main environmental topics in the news, unemployment and sovereign debt were high on the agenda of politicians—some topics change, others remain.

Looking forward to 2039, the impacts of climate change will have amplified: invasive species—both plants such as ambrosia and animals such as the tiger mosquito—will have advanced further northward in Europe, while intensive agriculture in Scotland and Scandinavia will have become the norm—the European Union (EU) expects a 75 per cent increase in agricultural yields in these regions.

Other topics, such as bacteria which are resistant to antibiotics, represent a formidable challenge both as an opportunity for science and a risk to society. The European Commission estimates that today, 25,000 people die annually as a result of an infection with multi-drug-resistant bacteria.

The ageing population is another major opportunity and risk in the hands of policymakers, a topic which The Geneva Association started analysing more than 25 years ago. Yet the multiple benefits of continued activity by the elderly—such as lower health costs—are only starting to be recognised by politicians. And most companies, organisations and administrations are still extremely hesitant to keep able employees beyond the legal age of retirement.

No easy predictions can be made on the outcome of societal changes. Trends such as a shift from science-based policymaking to policy-based science, from evidence-based advocacy to advocacy-based evidence and from fault-based liability to need-based compensation could lead society onto down the wrong path, which may be irreversible.

The last paragraph from the excerpt is the most interesting to me as its puts some of the current machinations within Canadian public life into context within the European (and I suspect the international) political scene.

I do have a comment or two about the research but first here’s a citation for it,

Insurance Market Perception of Nanotechnology and Nanomaterials Risks By Lijana Baublyte, Martin Mullins, Finbarr Murphy and Syed A.M. Tofai. Geneva Association Newsletter: Risk Management, No. 54, June 2014.

No date is offered for when the research was conducted and there is no indication in the newsletter that it was published prior to its June 2014 publication.

As for the research itself, first, the respondents are self-assessing their knowledge about nanotechnology. That presents an interesting problem for researchers since self-assessment in any area is highly dependent on various attributes such as confidence, perceived intelligence, etc. For example, someone who’s more knowledgeable might self-assess as being less so than someone who has more confidence in themselves. As for this statistic from the report,

… Over 40 per cent of surveyed laypeople heard nothing at all about nanotechnologies and nanomaterials, 47.5 per cent said they were vaguely familiar with the technology and the remaining 11.7 per cent of respondents reported having moderate working knowledge.

Generally, people won’t tell you that they know about nanotechnologies and nanomaterials from a video game (Deux Ex) or a comic book (Iron Man’s Extremis story line) as they may not consider that to be knowledge or are embarrassed. In the case of the video game, the information about nanotechnology is based on reputable scientific research although it is somewhat massaged to fit into the game ethos. Nonetheless, information about emerging technologies is often conveyed through pop culture properties and/or advertising and most researchers don’t take that into account.

One more thing about layperson awareness, the researchers cite a meta-analysis conducted by Terre Satterfield, et. al. (full citation: Satterfield, T., Kandlikar, M., Beaudrie, C.E.H., Conti,J., and Herr Harthorn, B. [2009]. Anticipating the perceived risk of nanotechnologies. Nature Nanotechnology, 4[11]: 752–758),  which was published in 2009 (mentioned in my Sept. 22, 2009 post; scroll down about 35% of the way). As I recall, the meta-analysis fell a bit short as the researchers didn’t provide in-depth analysis of the research instruments (questionnaires) instead analysing only the results. That said, one can’t ‘reinvent the wheel’ every time one writes a paper or analyses data although I do wish just once I’d stumble across a study where researchers analysed the assumptions posed by the wording of the questions.

Singaporeans’ perceptions of nanotechnology and consumer attitudes towards nanotechnologies in food production

This is the first time I’ve seen a study about nanotechnology perception and awareness from Asia. (As I’m sure this is not the first or the only such study, I lament my language skills once more. Since my primary search is for English language materials with my second language, French, as a very distant second, I am limited to translated materials.)

This piece of research comes from Singapore. From a Dec. 11, 2014 news item on the Asian Scientist magazine website,

A survey published in the Journal of Nanoparticle Research shows that while the Singaporean population is more familiar with nanotechnology than their Western counterparts in the US and Europe, they are also more wary of the risks involved.

Asia is expected to dominate the use and release of nanomaterials into the environment, largely due to the size of the population. Furthermore, the region in general—and Singapore in particular—has invested heavily in nanotechnology research, rapidly translating their findings into industrial and consumer products. However, there has been a lack of studies documenting public attitudes and acceptance of new technologies such as nanotechnology.

To address this gap of information, a team of researchers led by first author Dr. Saji George from the Nanyang Polytechnic (NYP) Center for Sustainable Nanotechnology conducted a survey of 1,080 Singaporeans above the age of 15. Their results revealed that approximately 80 percent had some understanding of nanotechnology.

A June 20, 2014 Nanyang Polytechnic media release provides additional details about the research,

In a recent public perception study conducted in Singapore with 1,000 respondents, researchers from Nanyang Polytechnic’s (NYP) Centre for Sustainable Nanotechnology (CSN) found that 80% of respondents were aware of nanotechnology, while only 40% of them were positive about its benefits. This was shared at the official launch of the CSN today. The event was graced by Mr Derek Ho, Director-General, Environmental Public Health Division, National Environment Agency (NEA).

The Centre is the first-of-its-kind among institutes of higher learning (IHLs) in Singapore. It is dedicated to studying the potential impact of novel engineered nanomaterials, and developing ways to ensure that nanotechnology applications are adopted in a sustainable manner for individuals and the environment. This makes the $1 million facility a key training facility for NYP’s students from the Schools of Chemical & Life Sciences, Engineering, and Health Sciences.

Perceptions influenced by exposure to prior information

The perception study conducted in collaboration with the United Kingdom’s Newcastle University, is part of a worldwide study. [emphasis mine] About 1,000 respondents were surveyed in Singapore. Among them, 80% had some level of familiarity with nanotechnology,  while only 40% of them were positive about its benefits. One of the strong determinants that influenced the perception of the public was their prior exposure to news on adverse effects of nanotechnology. This could be due to negative information on nanotechnology carried in the media. Often these are over interpretations of laboratory studies that tend to dampen public confidence in nanotechnology.

“Nanotechnology may be a double-edged sword in some applications. A large proportion of the population is already aware of it, and interestingly, 60% have actually come across negative information on nanotechnology. This points to the need for the Centre for Sustainable Nanotechnology to conduct its work robustly and effectively, to sharpen the benefits, and blunt the risks associated with nanotechnology. This will enable industries to better apply the relevant solutions, and for people to use products containing nanotechnology more confidently. Another impetus for the Centre is that through such studies, companies will learn what consumers are concerned about in specific types of products and how these concerns can be addressed during product design and manufacturing stages,” said Dr Joel Lee, Director of NYP’s School of Chemical & Life Sciences where the Centre is located.

The study also found variations in perception among different socio-demographic groups, and among applications of nanotechnology across different product ranges, for example food, baby products, medicine, clothing, cosmetics, water filters and electronics.

While this is a segue, there’s a very interesting tidbit about silver nanoparticles in this media release,

Smarter Antibacterial Nanotechnology

Since the CSN started operations in 2013, senior lecturers, Dr Saji George and Dr Hannah Gardner, from NYP’s Schools of Chemical & Life Sciences and Engineering, respectively, have studied the effectiveness of nano-silver in eliminating bacteria – which accounts for 30% of commercial nanotechnology – in applications currently available in the market. Nano-silver is largely used as an alternate anti-microbial solution in a range of industries, including clothing, baby products, personal care products and medicine.

Their research findings, now filed as a patent, uncovered that some drug resistant bacterial strains could also develop resistance to silver, contrary to the general notion that all bacterial strains will succumb to it. The duo then designed and developed a cost-effective method to generate cationic polymer coated silver nanoparticles. They observed that these nanoparticles could eliminate pathogenic bacteria regardless of their ability to resist antibiotics and silver.

Dr Lee added, “Nano-silver has captured the attention of industry and researchers. What we hope to achieve with the CSN is two-fold. We aim to be a resource for industries and even government regulatory agencies to tap on to better understand nanotechnology, its effects, and improve on its applications. These would also translate into real-world industry projects for our students and equip them to better serve the industry when they embark on their careers.”

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

Awareness on adverse effects of nanotechnology increases negative perception among public: survey study from Singapore by Saji George, Gulbanu Kaptan, Joel Lee, Lynn Frewer. Journal of Nanoparticle Research November 2014, 16:2751 Date: 22 Nov 2014

This paper is behind a paywall.

I did search for the “… worldwide study” regarding nanotechnology awareness and perceptions but found instead a recently published study on the topic of consumer attitudes towards nanotechnologies used in food production practices which features George and Frewer,

Consumer attitudes towards nanotechnologies applied to food production by L.J. Frewer, N. Gupta, S. George, A.R.H. Fischer, E.L. Giles, and D. Coles. Trends in Food Science & Technology, Volume 40, Issue 2, December 2014, Pages 211–225 (Special Issue: Nanotechnology in Foods: Science behind and future perspectives)

This article is behind a paywall.

Molecular robots (nanobots/nanorobots): a promising start at Oxford University

‘Baby steps’ is how they are describing the motion and the breakthrough in functional molecular robots at the University of Oxford. From a Dec. 11, 2014 news item on phys.org,

A walking molecule, so small that it cannot be observed directly with a microscope, has been recorded taking its first nanometre-sized steps.

It’s the first time that anyone has shown in real time that such a tiny object – termed a ‘small molecule walker’ – has taken a series of steps. The breakthrough, made by Oxford University chemists, is a significant milestone on the long road towards developing ‘nanorobots’.

‘In the future we can imagine tiny machines that could fetch and carry cargo the size of individual molecules, which can be used as building blocks of more complicated molecular machines; imagine tiny tweezers operating inside cells,’ said Dr Gokce Su Pulcu of Oxford University’s Department of Chemistry. ‘The ultimate goal is to use molecular walkers to form nanotransport networks,’ she says.

A Dec. 10, 2014 University of Oxford science blog post by Pete Wilton, which originated the news item, describes one of the problem with nanorobots,

However, before nanorobots can run they first have to walk. As Su explains, proving this is no easy task.

For years now researchers have shown that moving machines and walkers can be built out of DNA. But, relatively speaking, DNA is much larger than small molecule walkers and DNA machines only work in water.

The big problem is that microscopes can only detect moving objects down to the level of 10–20 nanometres. This means that small molecule walkers, whose strides are 1 nanometre long, can only be detected after taking around 10 or 15 steps. It would therefore be impossible to tell with a microscope whether a walker had ‘jumped’ or ‘floated’ to a new location rather than taken all the intermediate steps.

The post then describes how the researchers solved the problem,

… Su and her colleagues at Oxford’s Bayley Group took a new approach to detecting a walker’s every step in real time. Their solution? To build a walker from an arsenic-containing molecule and detect its motion on a track built inside a nanopore.

Nanopores are already the foundation of pioneering DNA sequencing technology developed by the Bayley Group and spinout company Oxford Nanopore Technologies. Here, tiny protein pores detect molecules passing through them. Each base disrupts an electric current passed through the nanopore by a different amount so that the DNA base ‘letters’ (A, C, G or T) can be read.

In this new research, they used a nanopore containing a track formed of five ‘footholds’ to detect how a walker was moving across it.

‘We can’t ‘see’ the walker moving, but by mapping changes in the ionic current flowing through the pore as the molecule moves from foothold to foothold we are able to chart how it is stepping from one to the other and back again,’ Su explains.

To ensure that the walker doesn’t float away, they designed it to have ‘feet’ that stick to the track by making and breaking chemical bonds. Su says: ‘It’s a bit like stepping on a carpet with glue under your shoes: with each step the walker’s foot sticks and then unsticks so that it can move to the next foothold.’ This approach could make it possible to design a machine that can walk on a variety of surfaces.

There is a video illustrating the molecular walker’s motion, (courtesy University of Oxford),

There is as noted in Wilton’s post, more work to do,

It’s quite an achievement for such a tiny machine but, as Su is the first to admit, there are many more challenges to be overcome before programmable nanorobots are a reality.

‘At the moment we don’t have much control over which direction the walker moves in; it moves pretty randomly,’ Su tells me. ‘The protein track is a bit like a mountain slope; there’s a direction that’s easier to walk in so walkers will tend to go this way. We hope to be able to harness this preference to build tracks that direct a walker where we want it to go.’

The next challenge after that will be for a walker to make itself useful by, for instance, carrying a cargo: there’s already space for it to carry a molecule on its ‘head’ that it could then take to a desired location to accomplish a task.

Su comments: ‘We should be able to engineer a surface where we can control the movement of these walkers and observe them under a microscope through the way they interact with a very thin fluorescent layer. This would make it possible to design chips with different stations with walkers ferrying cargo between these stations; so the beginnings of a nanotransport system.’

These are the first tentative baby steps of a new technology, but they promise that there could be much bigger strides to come.

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

Continuous observation of the stochastic motion of an individual small-molecule walker by Gökçe Su Pulcu, Ellina Mikhailova, Lai-Sheung Choi, & Hagan Bayley. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.264 Published online 08 December 2014

This paper is behind a paywall.

Projecting beams of light from contact lenses courtesy of Princeton University (US)

Princeton University’s 3D printed contact lenses with LED (light-emitting diodes) included are not meant for use by humans or other living beings but they are a flashy demonstration. From a Dec. 10, 2014 news item on phys.org,

As part of a project demonstrating new 3-D printing techniques, Princeton researchers have embedded tiny light-emitting diodes into a standard contact lens, allowing the device to project beams of colored light.

Michael McAlpine, the lead researcher, cautioned that the lens is not designed for actual use—for one, it requires an external power supply. Instead, he said the team created the device to demonstrate the ability to “3-D print” electronics into complex shapes and materials.

“This shows that we can use 3-D printing to create complex electronics including semiconductors,” said McAlpine, an assistant professor of mechanical and aerospace engineering. “We were able to 3-D print an entire device, in this case an LED.”

A Dec. 9, 2014 Princeton University news release by John Sullivan, which originated the news item, describes the 3D lens, the objectives for this project, and an earlier project involving a ‘bionic ear’ in more detail (Note: Links have been removed),

The hard contact lens is made of plastic. The researchers used tiny crystals, called quantum dots, to create the LEDs that generated the colored light. Different size dots can be used to generate various colors.

“We used the quantum dots [also known as nanoparticles] as an ink,” McAlpine said. “We were able to generate two different colors, orange and green.”

The contact lens is also part of an ongoing effort to use 3-D printing to assemble diverse, and often hard-to-combine, materials into functioning devices. In the recent past, a team of Princeton professors including McAlpine created a bionic ear out of living cells with an embedded antenna that could receive radio signals.

Yong Lin Kong, a researcher on both projects, said the bionic ear presented a different type of challenge.

“The main focus of the bionic ear project was to demonstrate the merger of electronics and biological materials,” said Kong, a graduate student in mechanical and aerospace engineering.

Kong, the lead author of the Oct. 31 [2014] article describing the current work in the journal Nano Letters, said that the contact lens project, on the other hand, involved the printing of active electronics using diverse materials. The materials were often mechanically, chemically or thermally incompatible — for example, using heat to shape one material could inadvertently destroy another material in close proximity. The team had to find ways to handle these incompatibilities and also had to develop new methods to print electronics, rather than use the techniques commonly used in the electronics industry.

“For example, it is not trivial to pattern a thin and uniform coating of nanoparticles and polymers without the involvement of conventional microfabrication techniques, yet the thickness and uniformity of the printed films are two of the critical parameters that determine the performance and yield of the printed active device,” Kong said.

To solve these interdisciplinary challenges, the researchers collaborated with Ian Tamargo, who graduated this year with a bachelor’s degree in chemistry; Hyoungsoo Kim, a postdoctoral research associate and fluid dynamics expert in the mechanical and aerospace engineering department; and Barry Rand, an assistant professor of electrical engineering and the Andlinger Center for Energy and the Environment.

McAlpine said that one of 3-D printing’s greatest strengths is its ability to create electronics in complex forms. Unlike traditional electronics manufacturing, which builds circuits in flat assemblies and then stacks them into three dimensions, 3-D printers can create vertical structures as easily as horizontal ones.

“In this case, we had a cube of LEDs,” he said. “Some of the wiring was vertical and some was horizontal.”

To conduct the research, the team built a new type of 3-D printer that McAlpine described as “somewhere between off-the-shelf and really fancy.” Dan Steingart, an assistant professor of mechanical and aerospace engineering and the Andlinger Center, helped design and build the new printer, which McAlpine estimated cost in the neighborhood of $20,000.

McAlpine said that he does not envision 3-D printing replacing traditional manufacturing in electronics any time soon; instead, they are complementary technologies with very different strengths. Traditional manufacturing, which uses lithography to create electronic components, is a fast and efficient way to make multiple copies with a very high reliability. Manufacturers are using 3-D printing, which is slow but easy to change and customize, to create molds and patterns for rapid prototyping.

Prime uses for 3-D printing are situations that demand flexibility and that need to be tailored to a specific use. For example, conventional manufacturing techniques are not practical for medical devices that need to be fit to a patient’s particular shape or devices that require the blending of unusual materials in customized ways.

“Trying to print a cellphone is probably not the way to go,” McAlpine said. “It is customization that gives the power to 3-D printing.”

In this case, the researchers were able to custom 3-D print electronics on a contact lens by first scanning the lens, and feeding the geometric information back into the printer. This allowed for conformal 3-D printing of an LED on the contact lens.

Here’s what the contact lens looks like,

Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton, is leading a research team that uses 3-D printing to create complex electronics devices such as this light-emitting diode printed in a plastic contact lens. (Photos by Frank Wojciechowski)

Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton, is leading a research team that uses 3-D printing to create complex electronics devices such as this light-emitting diode printed in a plastic contact lens. (Photos by Frank Wojciechowski)

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

3D Printed Quantum Dot Light-Emitting Diodes by Yong Lin Kong, Ian A. Tamargo, Hyoungsoo Kim, Blake N. Johnson, Maneesh K. Gupta, Tae-Wook Koh, Huai-An Chin, Daniel A. Steingart, Barry P. Rand, and Michael C. McAlpine. Nano Lett., 2014, 14 (12), pp 7017–7023 DOI: 10.1021/nl5033292 Publication Date (Web): October 31, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

I’m always a day behind for Dexter Johnson’s postings on the Nanoclast blog (located on the IEEE [institute of Electrical and Electronics Engineers]) so I didn’t see his Dec. 11, 2014 post about these 3Dprinted LED[embedded contact lenses until this morning (Dec. 12, 2014). In any event, I’m excerpting his very nice description of quantum dots,

The LED was made out of the somewhat exotic nanoparticles known as quantum dots. Quantum dots are a nanocrystal that have been fashioned out of semiconductor materials and possess distinct optoelectronic properties, most notably fluorescence, which makes them applicable in this case for the LEDs of the contact lens.

“We used the quantum dots [also known as nanoparticles] as an ink,” McAlpine said. “We were able to generate two different colors, orange and green.”

I encourage you to read Dexter’s post as he provides additional insights based on his long-standing membership within the nanotechnology community.

Do Tenebrionind beetles collect dew or condensation—a water issue at the nanoscale

Up until now, the research I’ve stumbled across about Tenebrionind beetles and their water-collecting ways has been from the US but this latest work comes from a France/Spain,/UK collaboration which focused on a specific question, exactly where do these beetles harvest their water from? A Dec. 8, 2014 news item on Nanotechnology Now describes this latest research,

Understanding how a desert beetle harvests water from dew could improve drinking water collection in dew condensers

Insects are full of marvels – and this is certainly the case with a beetle from the Tenebrionind family, found in the extreme conditions of the Namib desert. Now, a team of scientists has demonstrated that such insects can collect dew on their backs – and not just fog as previously thought. This is made possible by the wax nanostructure on the surface of the beetle’s elytra. … They bring us a step closer to harvesting dew to make drinking water from the humidity in the air. This, the team hopes, can be done by improving the water yield of man-made dew condensers that mimick the nanostructure on the beetle’s back.

A Dec. 8, 2014  Springer press release (also on EurekAlert), which originated the news item, describes how this research adds to the body of knowledge about the ability to harvest water from the air,

It was not clear from previous studies whether water harvested by such beetles came from dew droplets, in addition to fog. Whereas fog is made of ready-made microdroplets floating in the air, dew appears following the cooling of a substrate below air temperature. This then turns the humidity of air into tiny droplets of water because more energy – as can be measured through infrared emissions – is sent to the atmosphere than received by it. The cooling capability is ideal, they demonstrated, because the insect’s back demonstrates near-perfect infrared emissivity.

Guadarrama-Cetina [José Guadarrama-Cetina] and colleagues also performed an image analysis of dew drops forming on the insect’s back on the surface of the elytra, which appears as a series of bumps and valleys. Dew primarily forms in the valleys endowed with a hexagonal microstructure, they found, unlike the smooth surface of the bumps. This explains how drops can slide to the insect’s mouth when they reach a critical size.

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

Dew condensation on desert beetle skin by J.M. Guadarrama-Cetina, A. Mongruel, M.-G. Medici, E. Baquero, A.R. Parker, I. Milimouk-Melnytchuk, W. González-Viñas, and D. Beysens. Eur. Phys. J. E (European Physics Journal E 2014) 37: 109, DOI 10.1140/epje/i2014-14109-y

This paper is currently (Dec. 8, 2014) open access. I do not know if this will be permanent or if access rights will change over time.

My previous postings on the topic of water and beetles have focused on US research of the Stenocara beetle (aka Namib desert beetle) which appears to be a member of the Tenebrionind family of beetles mentioned in this latest research.

The European researchers have provided an image of the beetle they were examining,

A preserved specimen of the Tenebrionind beetle (Physasterna cribripes) was used for this study, displaying the insect’s mechanisms of dew harvesting. © J.M. Guadarrama-Cetina et al.

A preserved specimen of the Tenebrionind beetle (Physasterna cribripes) was used for this study, displaying the insect’s mechanisms of dew harvesting. © J.M. Guadarrama-Cetina et al.

As for my other pieces on this topic, there’s a July 29, 2014 post, a June 18, 2014 post, and a Nov. 26, 2012 post.

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.