Topological insulators (TIs) are an exciting new type of material that on their surface carry electric current, but within their bulk, act as insulators. Since the discovery of TIs about a decade ago, their unique characteristics (which point to potential applications in quantum computing) have been explored theoretically, and in the last five years, experimentally. But where in theory, the bulk of TIs carry no current, in the laboratory, impurities and disorder in real materials mean that the bulk is, in fact, conductive. This has proven an obstacle to experimentation with TIs: findings from prior experiments designed to test the surface conductivity of TIs unavoidably included contributions from the surplus of electrons in the bulk. Now an interdisciplinary research team at the University of Illinois at Urbana-Champaign, in collaboration with researchers at Brookhaven National Laboratory’s Condensed Matter Physics and Materials Science Department, has measured superconductive surface states in TIs where the bulk charge carriers were successfully depleted. To deplete the electrons in the bulk, the team used three strategies: the TI material was doped with antimony, then it was doped at the surface with a chemical with strong electron affinity, and finally an electrostatic gate was used to apply voltage that lowered the energy of the entire system.
The University of Dayton Research Institute will benefit from the first round of applied research and development project awards the National Additive Manufacturing Innovation Institute announced in a few weeks ago. Rapid Prototype + Manufacturing LLC of Avon Lake, Ohio, was awarded $1 million for “Maturation of Fused Deposition Modeling Component Manufacturing,” and will contract with UD’s Research Institute for $575,000 for technology support and education. Other partners in the program, designed to resolve issues that have inhibited the transition to manufacturing of Fused Deposition Modeling, a popular thermoplastic-based additive process, include Stratasys of Eden Prairie, Minn., as well as aerospace companies Boeing, GE Aviation, Lockheed Martin and Northrop Grumman. “This program allows us to pool resources and leverage highly developed composites industry design practices to mature FDM manufacturing for aerospace and defense applications,” says Brian Rice, head of the Research Institute’s Multi-Scale Composites and Polymers Division. “UDRI’s role will be to analyze material properties and define how to design and certify parts manufactured for aerospace applications.” In July 2012, UDRI received $3 million from the Ohio Third Frontier to work with Stratasys, RP+M and additional partners to develop aircraft-engine components through additive manufacturing —also known as 3D printing—for several aerospace manufacturers.
Eliminating the defects at the interface separating two crystals, or grains, has been shown by nanotechnology experts to be a powerful strategy for making materials stronger, more easily molded, and less electrically resistant-or a host of other qualities sought by designers and manufacturers. Since 2004, when a seminal paper came out in Science, materials scientists have been excited about one special of arrangement of atoms in metals and other materials called a “coherent twin boundary” or CTB. Based on theory and experiment, these coherent twin boundaries are often described as “perfect,” appearing like a perfectly flat, one-atom-thick plane in computer models and electron microscope images. But new research now shows that coherent twin boundaries are not so perfect after all. A team of scientists at the University of Vermont’s College of Engineering and Mathematical Sciences and the Lawrence Livermore National Laboratory and elsewhere report that coherent twin boundaries found in copper “are inherently defective.” With a high-resolution electron microscope, using a more powerful technique than has ever been used to examine these boundaries, they found tiny kink-like steps and curvatures in what had previously been observed as perfect. Even more surprising, these kinks and other defects appear to be the cause of the coherent twin boundary’s strength and other desirable qualities. “Everything we have learned on these materials in the past 10 years will have to be revisited with this new information,” says UVM engineer Frederic Sansoz.
The DOE’s Fuel Cell Technologies Office has issued a request for information seeking feedback from interested stakeholders regarding the use of rotating disk electrode (RDE) experiments and best practices for experimental conditions for characterization of the activity and durability of proton exchange membrane fuel cell oxygen reduction reaction (ORR) electrocatalysts. A review of recent literature shows that the determination of the ORR activity has numerous intricacies that have not been systemically cataloged, resulting in values for the activity of Pt/C that vary significantly. Next steps will be to establish standard procedures and measurement parameters for the RDE technique so that novel catalysts can be benchmarked for ORR activity versus an accepted Pt/C baseline for polymer electrolyte fuel cell applications. DOE is specifically interested in information on best practices/protocols to enable consistency in procedures and less variability in results from different laboratories.
In a process comparable to squeezing an elephant through a pinhole, researchers at Missouri University of Science and Technology have designed a way to engineer atoms capable of funneling light through ultra-small channels. Their research is the latest in a series of recent findings related to how light and matter interact at the atomic scale, and it is the first to demonstrate that the material—a specially designed “meta-atom” of gold and silicon oxide—can transmit light through a wide bandwidth and at a speed approaching infinity. The meta-atoms’ broadband capability could lead to advances in optical devices, which currently rely on a single frequency to transmit light, the researchers say. ”These meta-atoms can be integrated as building blocks for unconventional optical components with exotic electromagnetic properties over a wide frequency range,” write Jie Gao and Xiaodong Yang, assistant professors of mechanical engineering at Missouri S&T, and Lei Sun, a visiting scholar at the university. The researchers created mathematical models of the meta-atom, a material 100 nanometers wide and 25 nanometers tall that combined gold and silicon oxide in stairstep fashion. In their simulations, the researchers stacked 10 of the meta-atoms, then shot light through them at various frequencies. They found that when light encountered the material in a range between 540 terahertz and 590 terahertz, it “stretched” into a nearly straight line and achieved an “effective permittivity” known as epsilon-near-zero. Effective permittivity refers to the ratio of light’s speed through air to its speed as it passes through a material. As light passes through the engineered meta-atoms described by Gao and Yang, however, its effective permittivity reaches a near-zero ratio. In other words, through the medium of these specially designed materials, light actually travels faster than the speed of light. It travels “infinitely fast” through this medium, Yang says.
Acting Secretary of Energy Daniel Poneman announced that DOE is awarding 88 grants to small businesses in 28 states to develop clean energy technologies with a strong potential for commercialization and job creation. These awards, totaling over $16 million in investments, will help small businesses with promising ideas that could improve manufacturing processes, boost the efficiency of buildings, reduce reliance on foreign oil, and generate electricity from renewable sources. Companies competing for these grants were encouraged to propose outside-the-box innovations to meet ambitious cost and performance targets. The small businesses receiving the awards are located in 28 states: Alabama, Arizona, Arkansas, California, Colorado, Delaware, Florida, Georgia, Illinois, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Pennsylvania, Tennessee, Texas, Utah, Virginia, and Washington. Companies competing for these grants were encouraged to propose outside-the-box innovations to meet ambitious cost and performance targets. The selections are for Phase I and Fast Track (combined Phase I and II) work. That means that the new projects will go toward exploring the feasibility of innovative concepts that could be developed into prototype technologies. Seventy-nine awards will go to SBIR projects, and another nine will go to STTR projects.
Atomic force microscope image of 50-nm diameter silica nanoparticles on PTFE surface. Researchers at the University of Arkansas found that relatively low concentrations of the particles greatly improved PTFE wear resistance. Credit: M. Zou, University of Arkansas
Well known as a nonstick surface in applications from kitchen tools to aerospace and medical components, polytetrafluoroethylene (Teflon) is getting a boost in wear resistance thanks to silica nanoparticles.
According to this press release, researchers at the University of Arkansas (Fayetteville) treated PTFE films with silica nanoparticles to significantly reduce wear while maintaining low friction in tests.
In a comparison of PTFE surfaces impregnated with silica nanoparticles versus pure PTFE films and bare stainless steel, the researchers found the composite films had greatly improved wear characteristics. All PTFE coatings were produced by dip coating type 316 stainless steel substrates.
According to researcher Min Zou, associate professor, director of the university’s Nano Mechanics and Tribology Laboratory (NMTL), and holder of the 21st Century Professorship in Mechanical Engineering, workers tested PTFE surfaces with two concentrations of 50-nm diameter silica nanoparticles—1.7 and 3.3 wt.%—against a conventional PTFE surface and bare stainless steel.
“Linear reciprocating wear tests were performed by repetitively rubbing the test samples against a chrome steel ball under an applied pressure up to 0.5 GPa,” Zou explained in an e-mail message. “The pure PTFE film failed immediately under 0.5 GPa pressure, while the composite film with 3.3 wt.% silica lasted 300 cycles.”
Results of the initial study were published in Tribology Transactions, a journal of the Society of Tribologists and Lubrication Engineers (Park Ridge, Ill.). The paper received the Society’s Al Sonntag Award for the best paper published on solid lubricants.
Zou and her team have continued their research with further development of the silica–PTFE composite material as well as testing of other types of nanoparticles in thin PTFE coatings, she reports. “The durability of the film has been increased four times compared to what we reported in this paper. If adding an adhesive layer, durability is increased 70 times. “
NMTL has developed a variety of nanoengineered surfaces (NESs), which are engineered with nanoscale topographies and chemistries to reduce friction and wear in tribological applications, change wetting properties of surfaces for anti-fogging and self-cleaning properties, and facilitate cell adhesion and growth in biomedical applications. Zou welcomes collaborative opportunities on novel methods of fabrication, characterization, and applications of NESs.
Last July’s 4th International Congress on Ceramics was the setting for multiple presentations on the use of advanced ceramics in various industries. Among the application areas covered were biology and medicine. This post is a recap of a paper on the topic from the May/June issue of AcerS’ International Journal of Applied Ceramic Technology.
According to author Vivek Pawar, a materials researcher at Smith and Nephew Inc. (Memphis, Tenn.), seven presentations at the event focused on bioceramics for orthopedic, tissue engineering, and dentistry applications, as well as on innovative manufacturing techniques and novel ceramic materials for use as bearing surfaces.
Pawar writes that the bioceramics used in hard or soft tissue replacement can be classified as bioactive glasses made mainly from calcium oxide, sodium oxide, phosphorus pentoxide, and silica; apatite-based ceramics made from synthetic hydroxyapatite and calcium phosphates; and ceramics that are used as bearing surfaces for orthopedic applications.
Since development of the first bioactive glass by Larry Hench more than 40 years ago, few alterations have been made to the materials’ composition. Pawar reports current research in the area focuses on developing compositions that maintain or increase bioactivity after crystallization during sintering. The goal is to develop low-density, easily machinable materials with fracture toughness greater than 1 MPa m1/2.
A new material aimed at meeting those criteria is a product called ‘Biosilicate’ from Vitrovita (São Carlos, Brazil), which is reported to have antimicrobial properties. In one study assessing the effectiveness of Biosilicate against a variety of microorganisms, the material displayed activity against all the bacteria except one, drastically reducing the number of viable cells in the first 10 minutes of contact.
Hydroxyapatite (HA) coatings are commonly used in orthopedic devices to promote bone in-growth on metallic implants. Pawar writes that current research focuses on increasing the material’s bioactivity by incorporating bioactive ions in the HA crystal structure. Researchers have investigated magnesium, strontium, silver, zinc, titanium, iron, sodium, and potassium cationic substitutions. Anionic substitutions considered include fluorine, chlorine, hydroxide, phosphate, and silicate ions. These ions perturb the HA crystal structure and change solubility. Current work is aimed at understanding how each of these ions affects bioactivity. Substitutions with silver, for example, have increased HA solubility and shown bactericidal effects.
Hip arthroplasty remains the predominant use for ceramic bearing surfaces in orthopedic implants, and materials used in this application have included alumina, yttria-stabilized zirconia, and zirconia-toughened alumina. Newer ceramic materials with higher strength and toughness than alumina and reduced risk of fracture include ‘Biolox delta‘ from CeramTec (Plochingen, Germany). A zirconia-toughened alumina with small additions of chromium oxide and strontium aluminate, the material is “being considered for challenging applications such as hip resurfacing femoral heads and knee femoral components,” Pawar writes.
Another potential bearing material is silicon nitride, which offers high strength and toughness, excellent wear resistance, imaging compatibility, affinity to bone, and an antibacterial surface. Produced by Amedica (Salt Lake City, Utah), Si3N4 is already being used in spinal devices.
In the article Pawar notes, “Although no significant clinical problems have been reported with these two materials, a long-term clinical followup will be required to evaluate the performance of these materials.”
Innovations in ceramic processing techniques are being driven by specific biomedical applications. For example, camphene freeze casting processes are being used to create a 3-D interconnected porous bioceramic scaffold with the aim of producing a bioactive glass scaffold with high strength and bioactivity.
Also proposed is a 3-D printing process for apatite-based ceramics using stereolithography. The method is said to enable production of customized solutions based on clinical needs. A limited clinical study of the technology for repair of large craniofacial bone defects is under way at 3DCeram (Limoges, France).
Finally, nanoceramics with particle sizes of 1 to 100 nm are the focus of considerable research. The unique properties of materials produced using nanoparticles—higher surface-to-volume ratios, no light scattering, and unique mechanical properties in composite form—have led to use in dental fillings and crowns. Bone grafting, bone cement, and bioactive ceramic applications also offer research opportunities. Pawar expects future research in this area will focus on development of methods to produce customized nanoceramics based on patient needs.
Officials at the University of Dayton announced that the school has created a new research center focused on various thin-film investigations and applications. The initiative, dubbed the Center of Excellence in Thin-Film Research and Surface Engineering (CETRASE), hopes to deliver significant breakthroughs in everything from fuel and solar cell to optics, sensors, and electronics.
In a UD press release, Guru Subramanyam says, ”We want to find ways to make better, more efficient, cost-effective sensors, electronics, electro-optics, and energy systems and hopefully create new jobs in the region.”
Subramanyam, who is currently serving as leader of CETRASE, is chair of UD’s electrical and computer engineering department, and is one of several CETRASE faculty “team” members. The school says team members come also come for UD’s departments of materials engineering, biology, and physics as well as the electro-optics graduate program and the University of Dayton Research Institute.
Subramanyam says CETRASE provides the opportunity to move from ad hoc collaborations to strategic efforts and the pursuit of funding. “It makes sense for us to put our heads together for a center where we can coordinate activities, interact and share common equipment and costs. We also will have strength in numbers when submitting proposals as part of a center,” he says in the release.
In an interview, Subramanyam says before CETRASE was formed, “We had our own separate projects, funding applications and supporters. One or two of us would collaborate if we discovered an overlap, but as a group we didn’t come together until now. Now, for the first time, we will be developing joint priorities and funding proposals. Focusing on joint activities will be a change for us, but as a united group, I think we will be more attractive to funding agencies.”
“In addition,” Subramanyam continues, ”we will be holding regular CETRASE events, such as monthly seminars and bringing in invited guest speakers.”
Subramanyam notes that CETRASE has already hired its first dedicated staff member, a PhD who will serve as a coordinator of the center’s activities.
When I asked Subramanyam if CETRASE has any projects that might be of particular interest to the ceramics community, he says, “We have quite a bit of ceramic-related work going on, such as barium strontium titanate thin films for tunable dielectrics, yttrium barium copper oxide thin films and vanadium oxide research for the Air Force.”
He says that one immediate benefit is that CETRASE participants have access to team members’ advanced laser sources, pulse laser deposition systems, SEMs, TEMs, X-ray diffraction and Raman spectroscopy equipment, magnetron sputtering systems, and photolithography tools.
University spokesperson Shawn Robinson tells me UD’s materials engineering research currently ranks second in the nation based on research dollars.
In the last few weeks, GlaxoSmithKline finally (and relatively quietly) began the sale of its renowned Sensodyne Repair & Protect toothpaste in the United States, and if you think maybe I am going to write one of those good news/bad news stories, I am not. There is no good news here and I have scratched a bald spot in my wrinkled gray scalp over the past five days trying to make sense of GSK’s decision.
There are a lot of international readers of this blog, so some background is necessary to avoid confusion for those who live outside North America. For years, GSK has sold a unique and remarkable toothpaste outside North America called Sensodyne Repair & Protect. Materials scientists, particularly those that work with advanced glass materials, took interest in this Sensodyne product because it contained a form of the 45S5 Bioglass invented by Larry Hench. As far as I know, it was the first broad-based consumer product that contained a bioactive ingredient that was designed to stimulate the body to rebuild dental tissue that, heretofore, was not rebuildable.
Repair & Protect was reported to be a godsend to people (including most adults) whose teeth have become annoyingly sensitive to heat and cold. Typically, the sensitivity occurs as one ages because some of the tooth enamel gets worn off over the years, which exposes the dentinal tubules that connect with the tooth nerves.
The 45S5 glass particles in Repair & Protect solve this by triggering an ionic reaction. When the glass particles contact saliva and water, the glass releases calcium and phosphate ions that form a calcium phosphate layer. The body then converts this to hydroxyapatite, which creates a physical barrier over the tubules much like the original enamel. Brush twice a day with Repair & Protect and after two weeks the heat/cold sensitivity disappears.
Just for the record, it wasn’t a direct path from Hench’s lab to the innovative toothpaste. Hench licensed his 45S5 to a US startup company, NovaMin, created by a group of dentists who saw the enormous potential for the glass in dental applications. GSK also saw the enormous potential and bought NovaMin for $135 million three years ago.
Quickly, GSK started bringing Repair & Protect to markets in Europe, Asia, Australia, and South America, to name a few. Anecdotally, the product seems to have been well received by consumers (despite being priced at a premium) and dental professionals. I have not read any definitive reports on sales, but according to a December 2011 story on the Consumer Goods Technology website, “As of September 2011, GlaxoSmithKline had sold 20 million units of Sensodyne Repair & Protect in more than 30 international markets.” Not bad for a few months of sales.
And it got better. According to GSK’s 2011 Annual Report, its Sensodyne Sensitivity & Acid Erosion business “grew 16%, driven by the launch of Sensodyne Repair & Protect… . Since its launch in February 2011, Sensodyne Repair & Protect has been available in 30 markets across Europe, Asia and the Middle East, with 20 additional launches planned for 2012. The Sensodyne franchise has registered double-digit growth for 11 consecutive quarters.“
GSK’s 2012 Annual Report (pdf) makes it sound like the toothpaste quickly became one of its cash cows:
“The Oral care category led growth at 8% versus market growth of approximately 4%. Sensodyne became the business’s first ‘billion-dollar brand’ in 2012, boosted by the global roll-out of Sensodyne Repair & Protect and the launch of Sensodyne Repair & Protect Whitening and Extra Fresh.”
But, one of the obvious omissions, marketwise, was that GSK wouldn’t (or couldn’t) sell Repair & Protect in the US marketplace. The reason? Over the years I have spoken with several glass experts at various ACerS meetings and the story they gave was nearly always the same: GSK couldn’t get FDA approval. As recently as two months ago, I was told by someone involved with the product’s development—but not the FDA process—whose understanding was that US sales was delayed because the regulatory agency was fine with the toothpaste composition, but uneasy with the term “repair.” Regardless of the cause of the delay, you couldn’t buy similar Repair & Protect in the US. Even online outlets, such as Amazon, refused to ship the product to the US.
So far, I have been unable to confirm the story about the FDA delays, and I don’t know if there is any truth to it.
What I do know is true is that in the past three weeks, I suddenly starting hearing from friends and ACerS contacts that they either had seen Repair & Protect commercials on US networks or had seen an actual box of the product in US retail outlets. Great, I thought. No more having to sneak it into the US!
But, in fact, I still was a little skeptical because just a week or so ago, when he was receiving the Toledo Glass Award, Larry Hench stated something to the effect that Repair & Protect was unavailable in the US. Coincidentally, my colleague Eileen De Guire excitedly shot out an iPhone picture of a box of Repair & Protect that she just found in a drugstore in Michigan.
Weird, I thought. Then even my chiropractor on Monday mentioned to me that he had seen an ad for the toothpaste.
Curiosity fully piqued, I jumped online to look for GSK’s press release about the start of Repair and Protect sales in the US. There wasn’t one. I did look for the product on GSK’s website and was eventually directed to the US Sensodyne website. Indeed, the main story proclaimed, “Now a Sensodyne toothpaste that can actually repair sensitive teeth.” A-ha! It is true.
But… there was also button to click on to “Learn more about Repair & Protect.” I clicked hoping read carefully composed marketing copy about the benefits of the NovaMin/45S5 glass particles in Repair & Protect like that on the UK Sensodyne website.
Boy, was I disappointed. Instead of a discussion of NovaMin, the webpage discusses the benefits of stannous fluoride. Stannous fluoride! The webpage also has video from a dentist whose chopped up testimonial has him saying, “I’m always open to new advances…” Now, if you are old enough to remember the old “Crest with Fluoristan” commercials, you know that there is nothing “advanced” about stannous fluoride.
I was certain there was a mistake. I was so certain there was a mistake that I went out to my local CVS to buy a tube so I could read the ingredients myself. Sure enough, the only active ingredient is “stannous fluoride 0.454%.”
I should have been tipped off by the relatively quiet start of the sales of Repair & Protect in the US. Yes, GSK/Sensodyne is running TV ads in the US, but it defies logic that a major consumer product company rolls out a “billion-dollar” brand in a huge market without 1) a press release and press push, 2) social media promotions ($1 off coupon campaigns don’t count), 3) an education campaign aimed at dentists, and 4) some nearly-over-the-top promotional events. But, that is what it appears GSK is doing.
I twice requested an interview with a GSK representative to explain why GSK switched the formulation for the US version of Repair & Protect and why there was such a lackluster product rollout. GSK refused to provide an interview opportunity. Instead, I had to settle for an insipid exchange of emails with GSK’s media contact for North America consumer products, Deborah Bolding.
Bolding wrote to me, “Sensodyne Repair and Protect is a new product here in the US and does not contain NovaMin. The FDA approved the formulation. We work with regulatory authorities in each market on formulations for the specific product to be marketed and sold in that specific market. There are variances by market depending on the local regulatory body and other factors.”
When I asked for examples of other markets where Repair & Protect doesn’t contain 45S5/NovaMin, she didn’t respond other than to write, “As mentioned earlier, formulations vary by market because each market has its own regulatory authorities.”
When I requested that Bolding supply me contact information of the dentist featured in the testimonial video, Bolding responded, “I am pleased that I could address a number of your questions regarding Sensodyne Repair & Protect here in the US. Unfortunately, further comment will not be available on our strategy, rationale and future plans.”
So, advanced materials aficionados, I am sorry to conclude that if you want to buy Sensodyne Repair & Protect in the US, save your money and buy some Crest. If you want “real” Repair & Protect, you are still going to have to go abroad to buy it.
I am confident the story eventually will emerge about why GSK would invest $135 million in a US startup (NovaMin), but not leverage the technology to create a powerful product in the startup’s home nation—all at the risk of diluting and potentially damaging the Repair & Protect brand reputation outside the US. GSK is a publicly traded company, and maybe analysts and stockholders should start asking.