Tag Archives: Rice University

De-icing film for radar domes adapted for use on glass

Interesting to see that graphene is in use for de-icing. From a Sept. 16, 2014 news item  on ScienceDaily,

Rice University scientists who created a deicing film for radar domes have now refined the technology to work as a transparent coating for glass.

The new work by Rice chemist James Tour and his colleagues could keep glass surfaces from windshields to skyscrapers free of ice and fog while retaining their transparency to radio frequencies (RF).

A Sept. 16, 2014 Rice University news release on EurekAlert, which originated the news item, describes the technology and its new application in more detail,

The material is made of graphene nanoribbons, atom-thick strips of carbon created by splitting nanotubes, a process also invented by the Tour lab. Whether sprayed, painted or spin-coated, the ribbons are transparent and conduct both heat and electricity.

Last year the Rice group created films of overlapping nanoribbons and polyurethane paint to melt ice on sensitive military radar domes, which need to be kept clear of ice to keep them at peak performance. The material would replace a bulky and energy-hungry metal oxide framework.

The graphene-infused paint worked well, Tour said, but where it was thickest, it would break down when exposed to high-powered radio signals. “At extremely high RF, the thicker portions were absorbing the signal,” he said. “That caused degradation of the film. Those spots got so hot that they burned up.”

The answer was to make the films more consistent. The new films are between 50 and 200 nanometers thick – a human hair is about 50,000 nanometers thick – and retain their ability to heat when a voltage is applied. The researchers were also able to preserve their transparency. The films are still useful for deicing applications but can be used to coat glass and plastic as well as radar domes and antennas.

In the previous process, the nanoribbons were mixed with polyurethane, but testing showed the graphene nanoribbons themselves formed an active network when applied directly to a surface. They were subsequently coated with a thin layer of polyurethane for protection. Samples were spread onto glass slides that were then iced. When voltage was applied to either side of the slide, the ice melted within minutes even when kept in a minus-20-degree Celsius environment, the researchers reported.

“One can now think of using these films in automobile glass as an invisible deicer, and even in skyscrapers,” Tour said. “Glass skyscrapers could be kept free of fog and ice, but also be transparent to radio frequencies. It’s really frustrating these days to find yourself in a building where your cellphone doesn’t work. This could help alleviate that problem.”

Tour noted future generations of long-range Wi-Fi may also benefit. “It’s going to be important, as Wi-Fi becomes more ubiquitous, especially in cities. Signals can’t get through anything that’s metallic in nature, but these layers are so thin they won’t have any trouble penetrating.”

He said nanoribbon films also open a path toward embedding electronic circuits in glass that are both optically and RF transparent.

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

Functionalized Graphene Nanoribbon Films as a Radiofrequency and Optically Transparent Material by Abdul-Rahman O. Raji, Sydney Salters, Errol L. G. Samuel, Yu Zhu, Vladimir Volman, and James M. Tour. ACS Appl. Mater. Interfaces, Article ASAP DOI: 10.1021/am503478w Publication Date (Web): September 4, 2014
Copyright © 2014 American Chemical Society

This paper is behind a paywall.

De-icing is a matter of some interest in the airlines industry as I noted in my Nov. 19, 2012 posting about de-icing airplane wings.

Following the sound of a nanoparticle through the body

I was hoping for some actual sound files of nanoparticles in the body but for some rason the researchers don’t seem to have made them freely available. However, there is this textual description in a Sept. 5, 2014 news item on Nanowerk,

Nanoparticles have become interesting means for biomedical applications. Thanks to their minute dimensions and large surface areas, they can often penetrate cellular membranes and deliver high payloads of targeting agents and drugs to achieve better specificity and therapeutic effects than non-targeted treatments. Yet, quantitative in vivo measurements of nanoparticle concentrations are essential for nanotechnology-based preclinical research.

To date, tedious ex vivo analysis of nanoparticle concentrations in organs of test animals remains a standard approach in such biodistribution studies. Most current imaging methods remain limited due to several disadvantages and/or high costs. Optoacoustic tomography (OAT), a method that utilizes ultrasound generated by absorption of nanosecond-scale laser pulses to recreate an image of the absorbing volume based on the spatial variation of optical absorption coefficients, is a potential alternative.

Usually, due to the unknown light distribution in a complex optical scattering environment, tomographic images of live animals contain only qualitative information and are not suitable for quantitative biodistribution analysis. …

A Sept. 3, 2014 Wiley-VCH publishers press release by K. Maedefessel-Herrmann, which originated the news item, provides more details about the work,

… A team of researchers from TomoWave Laboratories, Inc., Rice University, and the University of Houston now developed a methodology to correlate changes in optoacoustic signal intensity from organs of live animals detected with OAT in relation to changes of optical absorption coefficient in those organs caused by nanoparticle accumulation.

The researchers quantified localized OAT brightness changes induced by accumulation of single-walled carbon nanotubes (SWCNTs) in liver, kidney and spleen of nude mice. Using the intrinsic fluorescence properties of disaggregated nanotubes, they measured SWCNT concentrations in the parts-per-million range in the harvested organs and defined the corresponding changes in optical absorption coefficient. The observed increases in optoacoustic signal brightness in tissues were compared with the increases in optical absorption coefficients caused by SWCNT accumulation.
The combination of these methods allows one to perform sensitivity calibration of an OAT system for a selected type of animal and for a range of optical absorption coefficient values of their organs to enable non-invasive concentration measurements of optically absorbing nanoparticles and dyes in vivo.

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

Enabling in vivo measurements of nanoparticle concentrations with three-dimensional optoacoustic tomography by Dmitri A. Tsyboulski, Anton V. Liopo, Richard Su, Sergey A. Ermilov, Sergei M. Bachilo, R. Bruce Weisman, and Alexander A. Oraevsky. Journal of Biophotonics, Volume 7, Issue 8, pages 581–588, August 2014. DOI: 10.1002/jbio.201200233  Article first published online: 2 APR 2013

This is an open access article.

Alberta’s summer of 2014 nano funding and the US nano community’s talks with the House of Representatives

I have two items concerning nanotechnology and funding. The first item features Michelle Rempel, Canada’s Minister of State for Western Economic Diversification (WD) who made two funding announcements this summer (2014) affecting the Canadian nanotechnology sector and, more specifically, the province of Alberta.

A June 20, 2014 WD Canada news release announced a $1.1M award to the University of Alberta,

Today, the Honourable Michelle Rempel, Minister of State for Western Economic Diversification, announced $1.1 million to help advance leading-edge atomic computing technologies.

Federal funds will support the University of Alberta with the purchase of an ultra-high resolution scanning tunneling microscope, which will enable researchers and scientists in western Canada and abroad to analyze electron dynamics and nanostructures at an atomic level. The first of its kind in North America, the microscope has the potential to significantly transform the semiconductor industry, as research findings aid in the prototype development and technology commercialization of new ultra low-power and low-temperature computing devices and industrial applications.

This initiative is expected to further strengthen Canada’s competitive position throughout the electronics value chain, such as microelectronics, information and communications technology, and the aerospace and defence sectors. The project will also equip graduate students with a solid foundation of knowledge and hands-on experience to become highly qualified, skilled individuals in today’s workforce.

One month later, a July 21, 2014 WD news release (hosted on the Alberta Centre for Advanced Micro and Nano Products [ACAMP]) announces this award,

Today, the Honourable Michelle Rempel, Minister of State for Western Economic Diversification, announced an investment of $3.3 million toward the purchase and installation of specialized advanced manufacturing and product development equipment at the Alberta Centre for Advanced Micro Nano Technology Products (ACAMP), as well as training on the use of this new equipment for small- and medium-sized enterprises (SMEs).

This support, combined with an investment of $800,000 from Alberta Innovates Technology Futures, will enable ACAMP to expand their services and provide businesses with affordable access to prototype manufacturing that is currently unavailable in western Canada. By helping SMEs accelerate the development and commercialization of innovative products, this project will help strengthen the global competitiveness of western Canadian technology companies.

Approximately 80 Alberta SMEs will benefit from this initiative, which is expected to result in the development of new product prototypes, the creation of new jobs in the field, as well as connections between SMEs and multi-national companies. This equipment will also assist ACAMP’s outreach activities across the western Canadian provinces.

I’m not entirely clear as to whether or not the June 2014 $1.1M award is considered part of the $3.3M award or if these are two different announcements. I am still waiting for answers to a June 20, 2014 query sent to Emily Goucher, Director of Communications to the Hon. Michelle Rempel,

Hi Emily!

Thank you for both the news release and the information about the embargo … happily not an issue at this point …

I noticed Robert Wolkow’s name in the release (I last posted about his work in a March 3, 2011 piece about his and his team’s entry into the Guinness Book of Records for the world’s smallest electron microscope tip (http://www.frogheart.ca/?tag=robert-wolkow) [Note: Wolkow was included in a list of quotees not included here in this July 29, 2014 posting]

I am assuming that the new microscope at the University of Alberta is specific to a different type of work than the one at UVic, which has a subatomic microscope (http://www.frogheart.ca/?p=10426)

Do I understand correctly that an STM is being purchased or is this an announcement of the funds and their intended use with no details about the STM available yet? After reading the news release closely, it looks to me like they do have a specific STM in mind but perhaps they don’t feel ready to make a purchase announcement yet?

If there is information about the STM that will be purchased I would deeply appreciate receiving it.

Thank you for your time.

As I wait, there’s more news from  the US as members of that country’s nanotechnology community testify at a second hearing before the House of Representatives. The first (a May 20, 2014 ‘National Nanotechnology Initiative’ hearing held before the Science, Space, and Technology
Subcommittee on Research and Technology) was mentioned in an May 23, 2014 posting  where I speculated about the community’s response to a smaller budget allocation (down to $1.5B in 2015 from $1.7B in 2014).

This second hearing is being held before the Energy and Commerce Subcommittee on Commerce, Manufacturing and Trade and features an appearance by James Tour from Rice University according to a July 28, 2014 news item on Azonano,

At the hearing, titled “Nanotechnology: Understanding How Small Solutions Drive Big Innovation,” Tour will discuss and provide written testimony on the future of nanotechnology and its impact on U.S. manufacturing and jobs. Tour is one of the most cited chemists in the country, and his Tour Group is a leader in patenting and bringing to market nanotechnology-based methods and materials.

Who: James Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry and professor of materials science and nanoengineering and of computer science.

What: Exploring breakthrough nanotechnology opportunities.

When: 10:15 a.m. EDT Tuesday, July 29.

Where: Room 2322, Rayburn House Office Building, Washington, D.C.

The hearing will explore the current state of nanotechnology and the direction it is headed so that members can gain a better understanding of the policy changes that may be necessary to keep up with advancements. Ultimately, the subcommittee hopes to better understand what issues will confront regulators and how to assess the challenges and opportunities of nanotechnology.

You can find a notice for this July 2014 hearing and a list of witnesses along with their statements here. As for what a second hearing might mean within the context of the US National Nanotechnology Initiative, I cannot say with any certainty. But, this is the first time in six years of writing this blog where there have been two hearings post-budget but as a passive collector of this kind of information this may be a reflection of my information collection strategies rather than a response to a smaller budget allocation. Still, it’s interesting.

Carbyne stretches from theory to reality and reveals its conundrum-type self

Rice University (Texas, US) scientists have taken a rather difficult material, carbyne, and twisted it to reveal new properties according to a July 21, 2014 news item on ScienceDaily,

Applying just the right amount of tension to a chain of carbon atoms can turn it from a metallic conductor to an insulator, according to Rice University scientists.

Stretching the material known as carbyne — a hard-to-make, one-dimensional chain of carbon atoms — by just 3 percent can begin to change its properties in ways that engineers might find useful for mechanically activated nanoscale electronics and optics.

A July 21, 2014 Rice University news release (also on EurekAlert), which originated the news item, describes carbyne and some of the difficulties the scientists addressed in their research on the material,

Until recently, carbyne has existed mostly in theory, though experimentalists have made some headway in creating small samples of the finicky material. The carbon chain would theoretically be the strongest material ever, if only someone could make it reliably.

The first-principle calculations by Yakobson and his co-authors, Rice postdoctoral researcher Vasilii Artyukhov and graduate student Mingjie Liu, show that stretching carbon chains activates the transition from conductor to insulator by widening the material’s band gap. Band gaps, which free electrons must overcome to complete a circuit, give materials the semiconducting properties that make modern electronics possible.

In their previous work on carbyne, the researchers believed they saw hints of the transition, but they had to dig deeper to find that stretching would effectively turn the material into a switch.

Each carbon atom has four electrons available to form covalent bonds. In their relaxed state, the atoms in a carbyne chain would be more or less evenly spaced, with two bonds between them. But the atoms are never static, due to natural quantum uncertainty, which Yakobson said keeps them from slipping into a less-stable Peierls distortion.

“Peierls said one-dimensional metals are unstable and must become semiconductors or insulators,” Yakobson said. “But it’s not that simple, because there are two driving factors.”

One, the Peierls distortion, “wants to open the gap that makes it a semiconductor.” The other, called zero-point vibration (ZPV), “wants to maintain uniformity and the metal state.”

Yakobson explained that ZPV is a manifestation of quantum uncertainty, which says atoms are always in motion. “It’s more a blur than a vibration,” he said. “We can say carbyne represents the uncertainty principle in action, because when it’s relaxed, the bonds are constantly confused between 2-2 and 1-3, to the point where they average out and the chain remains metallic.”

But stretching the chain shifts the balance toward alternating long and short (1-3) bonds. That progressively opens a band gap beginning at about 3 percent tension, according to the computations. The Rice team created a phase diagram to illustrate the relationship of the band gap to strain and temperature.

How carbyne is attached to electrodes also matters, Artyukhov said. “Different bond connectivity patterns can affect the metallic/dielectric state balance and shift the transition point, potentially to where it may not be accessible anymore,” he said. “So one has to be extremely careful about making the contacts.”

“Carbyne’s structure is a conundrum,” he said. “Until this paper, everybody was convinced it was single-triple, with a long bond then a short bond, caused by Peierls instability.” He said the realization that quantum vibrations may quench Peierls, together with the team’s earlier finding that tension can increase the band gap and make carbyne more insulating, prompted the new study.

“Other researchers considered the role of ZPV in Peierls-active systems, even carbyne itself, before we did,” Artyukhov said. “However, in all previous studies only two possible answers were being considered: either ‘carbyne is semiconducting’ or ‘carbyne is metallic,’ and the conclusion, whichever one, was viewed as sort of a timeless mathematical truth, a static ‘ultimate verdict.’ What we realized here is that you can use tension to dynamically go from one regime to the other, which makes it useful on a completely different level.”

Yakobson noted the findings should encourage more research into the formation of stable carbyne chains and may apply equally to other one-dimensional chains subject to Peierls distortions, including conducting polymers and charge/spin density-wave materials.

According to the news release the research was funded by the U.S. Air Force Office of Scientific Research, the Office of Naval Research Multidisciplinary University Research Initiative, and the Robert Welch Foundation. (I can’t recall another instance of the air force and the navy funding the same research.) In any event, here’s a link to and a citation for the paper,

Mechanically Induced Metal–Insulator Transition in Carbyne by Vasilii I. Artyukhov, Mingjie Liu, and Boris I. Yakobson. Nano Lett., Article ASAP DOI: 10.1021/nl5017317 Publication Date (Web): July 3, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

The researchers have provided an image to illustrate their work,

[downloaded from http://pubs.acs.org/doi/abs/10.1021/nl5017317]

[downloaded from http://pubs.acs.org/doi/abs/10.1021/nl5017317]

I’m not sure what the bird is doing in the image but it caught my fancy. There is another less whimsical illustration (you can see it in the  July 21, 2014 news item on ScienceDaily) and I believe the same caption can be used for the one I’ve chosen from the journal’s abstract page, “Carbyne chains of carbon atoms can be either metallic or semiconducting, according to first-principle calculations by scientists at Rice University. Stretching the chain dimerizes the atoms, opening a band gap between the pairs. Credit: Vasilii Artyukhov/Rice University.”

I last wrote about carbyne in an Oct. 9, 2013 posting where I noted that the material was unlikely to dethrone graphene as it didn’t appear to have properties useful in electronic applications. It seems the scientists have proved otherwise, at least in the laboratory.

Corporate influence, nanotechnology regulation, and Friends of the Earth (FoE) Australia

The latest issue of the newsletter, Chain Reaction # 121, July 2014, published by Friends of the Earth (FoE) Australia features an article by Louise Sales ‘Corporate influence over nanotechnology regulation‘ that has given me pause. From the Sales article,

I recently attended an Organisation for Economic Co-operation and Development (OECD) seminar on the risk assessment and risk management of nanomaterials. This was an eye-opening experience that graphically illustrated the extent of corporate influence over nanotechnology regulation globally. Representatives of the chemical companies DuPont and Evonik; the Nanotechnology Industries Association; and the Business and Industry Advisory Committee to the OECD (BIAC) sat alongside representatives of countries such as Australia, the US and Canada and were given equal speaking time.

BIAC gave a presentation on their work with the Canadian and United States Governments to harmonise nanotechnology regulation between the two countries. [US-Canada Regulatory Cooperative Council] [emphasis mine] Repeated reference to the involvement of ‘stakeholders’ prompted me to ask if any NGOs [nongovernmental organizations] were involved in the process. Only in the earlier stages apparently − ‘stakeholders’ basically meant industry.

A representative of the Nanotechnology Industries Association told us about the European NANoREG project they are leading in collaboration with regulators, industry and scientists. This is intended to ‘develop … new testing strategies adapted to innovation requirements’ and to ‘establish a close collaboration among authorities, industry and science leading to efficient and practically applicable risk management approaches’. In other words industry will be helping write the rules.

Interestingly, when I raised concerns about this profound intertwining of government and industry with one of the other NGO representatives they seemed almost dismissive of my concerns. I got the impression that most of the parties concerned thought that this was just the ‘way things were’. As under-resourced regulators struggle with the regulatory challenges posed by nanotechnology − the offer of industry assistance is probably very appealing. And from the rhetoric at the meeting one could be forgiven for thinking that their objectives are very similar − to ensure that their products are safe. Right? Wrong.

I just published an update about the US-Canada Regulatory Cooperation Council (RCC; in  my July 14, 2014 posting) where I noted the RCC has completed its work and final reports are due later this summer. Nowhere in any of the notices is there mention of BIAC’s contribution (whatever it might have been) to this endeavour.

Interestingly. BIAC is not an OECD committee but a separate organization as per its About us page,

BIAC is an independent international business association devoted to advising government policymakers at OECD and related fora on the many diversified issues of globalisation and the world economy.

Officially recognised since its founding in 1962 as being representative of the OECD business community, BIAC promotes the interests of business by engaging, understanding and advising policy makers on a broad range of issues with the overarching objectives of:

  • Positively influencing the direction of OECD policy initiatives;

  • Ensuring business and industry needs are adequately addressed in OECD policy decision instruments (policy advocacy), which influence national legislation;

  • Providing members with timely information on OECD policies and their implications for business and industry.

Through its 38 policy groups, which cover the major aspects of OECD work most relevant to business, BIAC members participate in meetings, global forums and consultations with OECD leadership, government delegates, committees and working groups.

I don’t see any mention of safety either in the excerpt or elsewhere on their About us page.

As Sales notes in her article,

Ultimately corporations have one primary driver and that’s increasing their bottom line.

I do wonder why there doesn’t seem to have been any transparency regarding BIAC’s involvement with the RCC and why no NGOs (according to Sales) were included as stakeholders.

While I sometimes find FoE and its fellow civil society groups a bit shrill and over-vehement at times, It never does to get too complacent. For example, who would have thought that General Motors would ignore safety issues (there were car crashes and fatalities as a consequence) over the apparently miniscule cost of changing an ignition switch. From What is the timeline of the GM recall scandal? on Vox.com,

March 2005: A GM project engineering manager closed the investigation into the faulty switches, noting that they were too costly to fix. In his words: “lead time for all solutions is too long” and “the tooling cost and piece price are too high.” Later emails unearthed by Reuters suggested that the fix would have cost GM 90 cents per car. [emphasis mine]

March 2007: Safety regulators inform GM of the death of Amber Rose, who crashed her Chevrolet Cobalt in 2005 after the ignition switch shut down the car’s electrical system and air bags failed to deploy. Neither the company nor regulators open an investigation.

End of 2013: GM determines that the faulty ignition switch is to blame for at least 31 crashes and 13 deaths.

According to a July 17, 2014 news item on CBC (Canadian Broadcasting Corporation) news online, Mary Barra, CEO of General Motors, has testified on the mater before the US Senate for a 2nd time, this year,

A U.S. Senate panel posed questions to a new set of key players Thursday [July 17, 2014] as it delves deeper into General Motors’ delayed recall of millions of small cars.

An internal report found GM attorneys signed settlements with the families of crash victims but didn’t tell engineers or top executives about mounting problems with ignition switches. It also found that GM’s legal staff acted without urgency.

GM says faulty ignition switches were responsible for at least 13 deaths. It took the company 11 years to recall the cars.

Barra will certainly be asked about how she’s changing a corporate culture that allowed a defect with ignition switches to remain hidden from the car-buying public for 11 years. It will be Barra’s second time testifying before the panel.

H/T ICON (International Council on Nanotechnology) July 16, 2014 news item. Following on the topic of transparency, ICON based at Rice University in Texas (US) has a Sponsors webpage.

Nanophotonics transforms Raman spectroscopy at Rice University (US)

This new technique for sensing molecules is intriguing. From a July 15, 2014 news item on Azonano,

Nanophotonics experts at Rice University [Texas, US] have created a unique sensor that amplifies the optical signature of molecules by about 100 billion times. Newly published tests found the device could accurately identify the composition and structure of individual molecules containing fewer than 20 atoms.

The new imaging method, which is described this week in the journal Nature Communications, uses a form of Raman spectroscopy in combination with an intricate but mass reproducible optical amplifier. Researchers at Rice’s Laboratory for Nanophotonics (LANP) said the single-molecule sensor is about 10 times more powerful that previously reported devices.

A July 15, 2014 Rice University news release (also on EurekAlert), which originated the news item, provides more detail about the research,

“Ours and other research groups have been designing single-molecule sensors for several years, but this new approach offers advantages over any previously reported method,” said LANP Director Naomi Halas, the lead scientist on the study. “The ideal single-molecule sensor would be able to identify an unknown molecule — even a very small one — without any prior information about that molecule’s structure or composition. That’s not possible with current technology, but this new technique has that potential.”

The optical sensor uses Raman spectroscopy, a technique pioneered in the 1930s that blossomed after the advent of lasers in the 1960s. When light strikes a molecule, most of its photons bounce off or pass directly through, but a tiny fraction — fewer than one in a trillion — are absorbed and re-emitted into another energy level that differs from their initial level. By measuring and analyzing these re-emitted photons through Raman spectroscopy, scientists can decipher the types of atoms in a molecule as well as their structural arrangement.

Scientists have created a number of techniques to boost Raman signals. In the new study, LANP graduate student Yu Zhang used one of these, a two-coherent-laser technique called “coherent anti-Stokes Raman spectroscopy,” or CARS. By using CARS in conjunction with a light amplifier made of four tiny gold nanodiscs, Halas and Zhang were able to measure single molecules in a powerful new way. LANP has dubbed the new technique “surface-enhanced CARS,” or SECARS.

“The two-coherent-laser setup in SECARS is important because the second laser provides further amplification,” Zhang said. “In a conventional single-laser setup, photons go through two steps of absorption and re-emission, and the optical signatures are usually amplified around 100 million to 10 billion times. By adding a second laser that is coherent with the first one, the SECARS technique employs a more complex multiphoton process.”

Zhang said the additional amplification gives SECARS the potential to address most unknown samples. That’s an added advantage over current techniques for single-molecule sensing, which generally require a prior knowledge about a molecule’s resonant frequency before it can be accurately measured.

Another key component of the SECARS process is the device’s optical amplifier, which contains four tiny gold discs in a precise diamond-shaped arrangement. The gap in the center of the four discs is about 15 nanometers wide. Owing to an optical effect called a “Fano resonance,” the optical signatures of molecules caught in that gap are dramatically amplified because of the efficient light harvesting and signal scattering properties of the four-disc structure.

Fano resonance requires a special geometric arrangement of the discs, and one of LANP’s specialties is the design, production and analysis of Fano-resonant plasmonic structures like the four-disc “quadrumer.” In previous LANP research, other geometric disc structures were used to create powerful optical processors.

Zhang said the quadrumer amplifiers are a key to SECARS, in part because they are created with standard e-beam lithographic techniques, which means they can be easily mass-produced.

“A 15-nanometer gap may sound small, but the gap in most competing devices is on the order of 1 nanometer,” Zhang said. “Our design is much more robust because even the smallest defect in a one-nanometer device can have significant effects. Moreover, the larger gap also results in a larger target area, the area where measurements take place. The target area in our device is hundreds of times larger than the target area in a one-nanometer device, and we can measure molecules anywhere in that target area, not just in the exact center.”

Halas, the Stanley C. Moore Professor in Electrical and Computer Engineering and a professor of biomedical engineering, chemistry, physics and astronomy at Rice, said the potential applications for SECARS include chemical and biological sensing as well as metamaterials research. She said scientific labs are likely be the first beneficiaries of the technology.

“Amplification is important for sensing small molecules because the smaller the molecule, the weaker the optical signature,” Halas said. “This amplification method is the most powerful yet demonstrated, and it could prove useful in experiments where existing techniques can’t provide reliable data.”

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

Coherent anti-Stokes Raman scattering with single-molecule sensitivity using a plasmonic Fano resonance by Yu Zhang, Yu-Rong Zhen, Oara Neumann, Jared K. Day, Peter Nordlander & Naomi J. Halas. Nature Communications 5, Article number: 4424 doi:10.1038/ncomms5424 Published 14 July 2014

This paper is behind a paywall.

Better RRAM memory devices in the short term

Given my recent spate of posts about computing and the future of the chip (list to follow at the end of this post), this Rice University [Texas, US] research suggests that some improvements to current memory devices might be coming to the market in the near future. From a July 12, 2014 news item on Azonano,

Rice University’s breakthrough silicon oxide technology for high-density, next-generation computer memory is one step closer to mass production, thanks to a refinement that will allow manufacturers to fabricate devices at room temperature with conventional production methods.

A July 10, 2014 Rice University news release, which originated the news item, provides more detail,

Tour and colleagues began work on their breakthrough RRAM technology more than five years ago. The basic concept behind resistive memory devices is the insertion of a dielectric material — one that won’t normally conduct electricity — between two wires. When a sufficiently high voltage is applied across the wires, a narrow conduction path can be formed through the dielectric material.

The presence or absence of these conduction pathways can be used to represent the binary 1s and 0s of digital data. Research with a number of dielectric materials over the past decade has shown that such conduction pathways can be formed, broken and reformed thousands of times, which means RRAM can be used as the basis of rewritable random-access memory.

RRAM is under development worldwide and expected to supplant flash memory technology in the marketplace within a few years because it is faster than flash and can pack far more information into less space. For example, manufacturers have announced plans for RRAM prototype chips that will be capable of storing about one terabyte of data on a device the size of a postage stamp — more than 50 times the data density of current flash memory technology.

The key ingredient of Rice’s RRAM is its dielectric component, silicon oxide. Silicon is the most abundant element on Earth and the basic ingredient in conventional microchips. Microelectronics fabrication technologies based on silicon are widespread and easily understood, but until the 2010 discovery of conductive filament pathways in silicon oxide in Tour’s lab, the material wasn’t considered an option for RRAM.

Since then, Tour’s team has raced to further develop its RRAM and even used it for exotic new devices like transparent flexible memory chips. At the same time, the researchers also conducted countless tests to compare the performance of silicon oxide memories with competing dielectric RRAM technologies.

“Our technology is the only one that satisfies every market requirement, both from a production and a performance standpoint, for nonvolatile memory,” Tour said. “It can be manufactured at room temperature, has an extremely low forming voltage, high on-off ratio, low power consumption, nine-bit capacity per cell, exceptional switching speeds and excellent cycling endurance.”

In the latest study, a team headed by lead author and Rice postdoctoral researcher Gunuk Wang showed that using a porous version of silicon oxide could dramatically improve Rice’s RRAM in several ways. First, the porous material reduced the forming voltage — the power needed to form conduction pathways — to less than two volts, a 13-fold improvement over the team’s previous best and a number that stacks up against competing RRAM technologies. In addition, the porous silicon oxide also allowed Tour’s team to eliminate the need for a “device edge structure.”

“That means we can take a sheet of porous silicon oxide and just drop down electrodes without having to fabricate edges,” Tour said. “When we made our initial announcement about silicon oxide in 2010, one of the first questions I got from industry was whether we could do this without fabricating edges. At the time we could not, but the change to porous silicon oxide finally allows us to do that.”

Wang said, “We also demonstrated that the porous silicon oxide material increased the endurance cycles more than 100 times as compared with previous nonporous silicon oxide memories. Finally, the porous silicon oxide material has a capacity of up to nine bits per cell that is highest number among oxide-based memories, and the multiple capacity is unaffected by high temperatures.”

Tour said the latest developments with porous silicon oxide — reduced forming voltage, elimination of need for edge fabrication, excellent endurance cycling and multi-bit capacity — are extremely appealing to memory companies.

“This is a major accomplishment, and we’ve already been approached by companies interested in licensing this new technology,” he said.

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

Nanoporous Silicon Oxide Memory by Gunuk Wang, Yang Yang, Jae-Hwang Lee, Vera Abramova, Huilong Fei, Gedeng Ruan, Edwin L. Thomas, and James M. Tour. Nano Lett., Article ASAP DOI: 10.1021/nl501803s Publication Date (Web): July 3, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

As for my recent spate of posts on computers and chips, there’s a July 11, 2014 posting about IBM, a 7nm chip, and much more; a July 9, 2014 posting about Intel and its 14nm low-power chip processing and plans for a 10nm chip; and, finally, a June 26, 2014 posting about HP Labs and its plans for memristive-based computing and their project dubbed ‘The Machine’.

‘Scotch-tape’ technique for isolating graphene

The ‘scotch-tape’ technique is mythologized in the graphene origins story which has scientists, Andre Geim and Konstantin Novoselov, first isolating the material by using adhesive (aka ‘sticky’ tape or ‘scotch’ tape) as per my Oct. 7, 2010 posting,

The technique that Geim and Novoselov used to create the first graphene sheets both amuses and fascinates me (from the article by Kit Eaton on the Fast Company website),

The two scientists came up with the technique that first resulted in samples of graphene–peeling individual atoms-deep sheets of the material from a bigger block of pure graphite. The science here seems almost foolishly simple, but it took a lot of lateral thinking to dream up, and then some serious science to investigate: Geim and Novoselo literally “ripped” single sheets off the graphite by using regular adhesive tape. Once they’d confirmed they had grabbed micro-flakes of the material, Geim and Novoselo were responsible for some of the very early experiments into the material’s properties. Novel stuff indeed, but perhaps not so unexpected from a scientist (Geim) who the Nobel Committe notes once managed to make a frog levitate in a magnetic field.

A May 21, 2014 article about Geim who has won both a Nobel and an Ig Nobel (the only scientist to do so) and graphene by Sarah Lewis for Fast Company offers more details about the discovery,

The graphene FNE [Friday Night Experiments] began when Geim asked Da Jiang, a doctoral student from China, to polish a piece of graphite an inch across and a few millimeters thick down to 10 microns using a specialized machine. Partly due to a language barrier, Jiang polished the graphite down to dust, but not the ultimate thinness Geim wanted.

Helpfully, the Geim lab was also observing graphite using scanning tunneling microscopy (STM). The experimenters would clean the samples beforehand using Scotch tape, which they would then discard. “We took it out of the trash and just used it,” Novoselov said. The flakes of graphite on the tape from the waste bin were finer and thinner than what Jiang had found using the fancy machine. They weren’t one layer thick—that achievement came by ripping them some more with Scotch tape.

They swapped the adhesive for Japanese Nitto tape, “probably because the whole process is so simple and cheap we wanted to fancy it up a little and use this blue tape,” Geim said. Yet “the method is called the ‘Scotch tape technique.’ I fought against this name, but lost.”

Scientists elsewhere have been inspired to investigate the process in minute detail as per a June 27, 2014 news item on Nanowerk,

The simplest mechanical cleavage technique using a primitive “Scotch” tape has resulted in the Nobel-awarded discovery of graphenes and is currently under worldwide use for assembling graphenes and other two-dimensional (2D) graphene-like structures toward their utilization in novel high-performance nanoelectronic devices.

The simplicity of this method has initiated a booming research on 2D materials. However, the atomistic processes behind the micromechanical cleavage have still been poorly understood.

A June 27, 2014 MANA (International Center for Materials Nanoarchitectoinics) news release, which originated the news item, provides more information,

A joined team of experimentalists and theorists from the International Center for Young Scientists, International Center for Materials Nanoarchitectonics and Surface Physics and Structure Unit of the National Institute for Materials Science, National University of Science and Technology “MISiS” (Moscow, Russia), Rice University (USA) and University of Jyväskylä (Finland) led by Daiming Tang and Dmitri Golberg for the first time succeeded in complete understanding of physics, kinetics and energetics behind the regarded “Scotch-tape” technique using molybdenum disulphide (MoS2) atomic layers as a model material.

The researchers developed a direct in situ probing technique in a high-resolution transmission electron microscope (HRTEM) to investigate the mechanical cleavage processes and associated mechanical behaviors. By precisely manipulating an ultra-sharp metal probe to contact the pre-existing crystalline steps of the MoS2 single crystals, atomically thin flakes were delicately peeled off, selectively ranging from a single, double to more than 20 atomic layers. The team found that the mechanical behaviors are strongly dependent on the number of layers. Combination of in situ HRTEM and molecular dynamics simulations reveal a transformation of bending behavior from spontaneous rippling (< 5 atomic layers) to homogeneous curving (~ 10 layers), and finally to kinking (20 or more layers).

By considering the force balance near the contact point, the specific surface energy of a MoS2 monoatomic layer was calculated to be ~0.11 N/m. This is the first time that this fundamentally important property has directly been measured.

After initial isolation from the mother crystal, the MoS2 monolayer could be readily restacked onto the surface of the crystal, demonstrating the possibility of van der Waals epitaxy. MoS2 atomic layers could be bent to ultimate small radii (1.3 ~ 3.0 nm) reversibly without fracture. Such ultra-reversibility and extreme flexibility proves that they could be mechanically robust candidates for the advanced flexible electronic devices even under extreme folding conditions.

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

Nanomechanical cleavage of molybdenum disulphide atomic layers by Dai-Ming Tang, Dmitry G. Kvashnin, Sina Najmaei, Yoshio Bando, Koji Kimoto, Pekka Koskinen, Pulickel M. Ajayan, Boris I. Yakobson, Pavel B. Sorokin, Jun Lou, & Dmitri Golberg. Nature Communications 5, Article number: 3631 doi:10.1038/ncomms4631 Published 03 April 2014

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

Harvest water from desert air with carbon nanotube cups (competition for NBD Nano?)

It’s been a while since I’ve seen Pulickel Ajayan’s name in a Rice University (Texas) news release and I wonder if this is the beginning of a series. I’ve noticed that researchers often publish a series of papers within a few months and then become quiet for two or more years as they work in their labs to gather more information.

This time the research from Pulickel’s lab has focused on the use of carbon nanotubes to harvest water from desert air. From a June 12, 2014 news item on Azonano,

If you don’t want to die of thirst in the desert, be like the beetle. Or have a nanotube cup handy.

New research by scientists at Rice University demonstrated that forests of carbon nanotubes can be made to harvest water molecules from arid desert air and store them for future use.

The invention they call a “hygroscopic scaffold” is detailed in a new paper in the American Chemical Society journal Applied Materials and Interfaces.

Researchers in the lab of Rice materials scientist Pulickel Ajayan found a way to mimic the Stenocara beetle, which survives in the desert by stretching its wings to capture and drink water molecules from the early morning fog.

Here’s more about the research from a June 11, 2014 Rice University news release (by Mike Williams?), which originated the news item,

They modified carbon nanotube forests grown through a process created at Rice, giving the nanotubes a superhydrophobic (water-repelling) bottom and a hydrophilic (water loving) top. The forest attracts water molecules from the air and, because the sides are naturally hydrophobic, traps them inside.

“It doesn’t require any external energy, and it keeps water inside the forest,” said graduate student and first author Sehmus Ozden. “You can squeeze the forest to take the water out and use the material again.”

The forests grown via water-assisted chemical vapor deposition consist of nanotubes that measure only a few nanometers (billionths of a meter) across and about a centimeter long.

The Rice team led by Ozden deposited a superhydrophobic layer to the top of the forest and then removed the forest from its silicon base, flipped it and added a layer of hydrophilic polymer to the other side.

In tests, water molecules bonded to the hydrophilic top and penetrated the forest through capillary action and gravity. (Air inside the forest is compressed rather then expelled, the researchers assumed.) Once a little water bonds to the forest canopy, the effect multiplies as the molecules are drawn inside, spreading out over the nanotubes through van der Waals forces, hydrogen bonding and dipole interactions. The molecules then draw more water in.

The researchers tested several variants of their cup. With only the top hydrophilic layer, the forests fell apart when exposed to humid air because the untreated bottom lacked the polymer links that held the top together. With a hydrophilic top and bottom, the forest held together but water ran right through.

But with a hydrophobic bottom and hydrophilic top, the forest remained intact even after collecting 80 percent of its weight in water.

The amount of water vapor captured depends on the air’s humidity. An 8 milligram sample (with a 0.25-square-centimeter surface) pulled in 27.4 percent of its weight over 11 hours in dry air, and 80 percent over 13 hours in humid air. Further tests showed the forests significantly slowed evaporation of the trapped water.

If it becomes possible to grow nanotube forests on a large scale, the invention could become an efficient, effective water-collection device because it does not require an external energy source, the researchers said.

Ozden said the production of carbon nanotube arrays at a scale necessary to put the invention to practical use remains a bottleneck. “If it becomes possible to make large-scale nanotube forests, it will be a very easy material to make,” he said.

This is not the first time researchers have used the Stenocara beetle (also known as the Namib desert beetle) as inspiration for a water-harvesting material. In a Nov. 26, 2012 posting I traced the inspiration  back to 2001 while featuring the announcement of a new startup company,

… US startup company, NBD Nano, which aims to bring a self-filling water bottle based on Namib desert beetle to market,

NBD Nano, which consists of four recent university graduates and was formed in May [2012], looked at the Namib Desert beetle that lives in a region that gets about half an inch of rainfall per year.

Using a similar approach, the firm wants to cover the surface of a bottle with hydrophilic (water-attracting) and hydrophobic (water-repellent) materials.

The work is still in its early stages, but it is the latest example of researchers looking at nature to find inspiration for sustainable technology.

“It was important to apply [biomimicry] to our design and we have developed a proof of concept and [are] currently creating our first fully-functional prototype,” Miguel Galvez, a co-founder, told the BBC.

“We think our initial prototype will collect anywhere from half a litre of water to three litres per hour, depending on local environments.”

You can find out more about NBD Nano here although they don’t give many details about the material they’ve developed. Given that MIT (Massachusetts Institute of Technology) researchers published a  paper about a polymer-based material laced with silicon nanoparticles inspired by the Namib beetle in 2006 and that NBD Nano is based Massachusetts, I believe NBD Nano is attempting to commercialize the material or some variant developed at MIT.

Getting back to Rice University and carbon nanotubes, this is a different material attempting to achieve the same goal, harvesting water from desert air. Here’s a link to and a citation for the latest paper inspired by the Stenocara beetle (Namib beetle),

Anisotropically Functionalized Carbon Nanotube Array Based Hygroscopic Scaffolds by Sehmus Ozden, Liehui Ge , Tharangattu N. Narayanan , Amelia H. C. Hart , Hyunseung Yang , Srividya Sridhar , Robert Vajtai , and Pulickel M Ajayan. ACS Appl. Mater. Interfaces, DOI: 10.1021/am5022717 Publication Date (Web): June 4, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

One final note, the research at MIT was funded by DARPA (US Defense Advanced Research Projects Agency). According to the news release the Rice University research held interest for similar agencies,

The U.S. Department of Defense and the U.S. Air Force Office of Scientific Research Multidisciplinary University Research Initiative supported the research.