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Microneedles fabricated with two-photon polymerization:
Credit: Royal Society of Chemistry

I first covered ACerS member Roger Narayan’s work in the field of two-photon polymerization a little more than a year ago in a story for ACerS’ membership magazine, the Bulletin. For several years, Narayan, a professor in the Joint Biomedical Engineering Department that is connected with NC State’s College of Engineering and the University of North Carolina at Chapel Hill, has been examining the use of this rapid prototyping approach using ceramic–polymer hybrid materials to create patient-specific microscale medical prostheses, scaffolds for tissue engineering and microscale medical devices.

One of set of applications he has been working on, in particular, is using two-photon polymerization to create arrays of fine microneedles. (Conceptually, Narayan’s polymerization process is like a 3D ink jet process that builds up structures on the nanoscale.)

Recently, Narayan coauthored a paper on the novel use of microneedles to deliver quantum dots into the skin. “Our findings are significant, in part, because this technology will potentially enable researchers to deliver quantum dots, suspended in solution, to deeper layers of skin. That could be useful for the diagnosis and treatment of skin cancers, among other conditions,” Narayan says in a news release from NCSU.

QDs, sometimes called “artificial atoms,” are semiconductor materials that fall into the category of nanocrystals, and they contain a variable number of electrons that occupy well-defined, discrete quantum states.

This groups is attracted to the use of QDs because of their ability to serve as fluorophores and also work as drug delivery vehicles. QD-based fluorescent probes can be engineered to be superior to organic dye fluorophore by being brighter and having better photostability (can fluoresce after one hour of continuous excitation), signal-to-noise ratio, emission ranges and fluorescent lifetimes. Researchers report they can use their intense fluorescence to track individual molecules.

Sample quantum dot with bio coating. Credit: Histesh R. Patel

At this point, Narayan and the other researchers just are using the microneedles on pig skin and can capture images of the quantum dots entering the skin using multiphoton microscopy. Although this work is still preliminary, these images allow the researchers to verify the basic effectiveness of the microneedles as a delivery mechanism for quantum dots.

The hope is that multiphoton microscopy will have clinical applications using real-time imaging materials such as the quantum dots for faster diagnosis of cancers or other medical problems.

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Grain boundary and adjacent space-charge. Credit: Conrad and Yang

According to a paper just published in Philosophy Magazine, researchers at North Carolina State University, who have been playing around with how ceramic materials behave in the presence of DC electric fields, apparently think they may have discovered an approach that could “revolutionize” ceramics manufacturing. At a minimum, they say that using a modest electric field can affect grain boundaries, and may make the process of shaping ceramics significantly more energy efficient and inexpensive compared with traditional manufacturing methods.

The researchers, lead by Hans Conrad, emeritus professor of materials science and engineering at NC State, wanted to look at how to influence the mechanical and electrical forces at grain boundaries in crystalline materials, such as ceramics.

“We found that if we apply an electric field to a material, it interacts with the charges at the grain boundaries and makes it easier for the crystals to slide against each other along these boundaries. This makes it much easier to deform the material,” says Conrad.

According to Conrad, the material becomes superplastic, allowing the ceramic to be shaped using a relatively small amount of force.

“We’ve found that you can bring the level of force needed to deform the ceramic material down to essentially zero, if a modest field is applied,” Conrad says. “We’re talking between 25 and 200 volts per centimeter, so the electricity from a conventional wall socket would be adequate for some applications.”

Diagram of DC electric field testing rig. Credit: Conrad and Yang

Conrad and his team say their findings could transform ceramic manufacturing of products from fuel cells to spark plugs to rocket nose cones. “It will make manufacturing processes more cost-effective and decrease related pollution,” Conrad says. “And these findings also hold promise for use in the development of new ceramic body armor.” Conrad says he intends to carry out more work particularly aimed at performance–cost improvements for body armor manufacturing

Conrad and Di Yang, a senior research associate at NC State, paper is titled, “Influence of an applied DC electric field on the plastic deformation kinetics of oxide ceramics.”

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Cross-sectional transmission electron microscope image of the functionally graded "smart" coating of hydroxyapatite with nano-silver particles distributed throughout. Credit: NCSU.

A team of North Carolina State University and Oak Ridge National Lab researchers have published a new paper that reports on the possibility of using hydroxyapatite layers seeded with silver particles - customized for each patient - as a coating on joint and bone replacements to help ward off infection.

The interesting idea the group is promoting is to combine two already-known concepts (the benefits of hydroxyapatite to counter rejection while promoting healing and the antimicrobial property of silver) with ion beam-assisted deposition technology to apply varying layers of hydroxyapatite–silver mix.

They tested coatings of functionally graded hydroxyapatite impregnated with nano silver particles (10–50 nm). They report that the amount of Ag (wt.%) on the outer surface of the FGHA ranged from 1.09 to 6.59, which was about half of the average Ag wt.% incorporated in the entire coating.

The group, which published their findings in Acta Biomaterialia, considers their innovation a “smart” material for two reasons. Afsaneh Rabiei, an NCSU associate professor of mechanical and aerospace engineering and one of the paper’s authors explains the first reason saying, ““We call it a smart coating because we can tailor the rate at which the amorphous layer dissolves to match the bone growth rate of each patient,” she says. Rabiei, who is also an associate faculty member of biomedical engineering, notes that this is important because people have very different rates of bone growth (e.g., young people’s bones tend to grow far faster than the bones of older adults).

The second reason they consider it to be a smart material is the variable rate of silver release. According to an NCSU news release, Rabiai says the hydroxyapatite coating allows the silver to be released rapidly after surgery, when there is more risk of infection, due to the faster dissolution of this amorphous layer of the coating. Conversely, the release of silver will continue for the life of the implant but will slow down as the patient heals.

The group also reports adhesion strengths comparable to FGHA without silver. The dominant failure mechanism was epoxy failure, and they report no observations of coating delamination.

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A team of engineers at North Carolina State University has created a small chip that can hold 1TB of data. That’s over 50 times the capacity of today’s silicon-based chip.

Led by Jagdish “Jay” Narayan, director of the National Science Foundation Center for Advanced Materials and Smart Structures at NCSU, the team said that their nanostructured Ni-MgO system can store up to 20 high-definition DVDs or 250 million pages of text.

Working at the nanoscale, the engineers added metal nickel to magnesium oxide. The resulting material contained clusters of nickel atoms no bigger than 10 square nanometers. The discovery represents a 90 percent size reduction compared with today’s techniques, and an advancement that could boost computer storage capacity. Underlying this is the team’s discovery that under certain conditions the Ni-MgO system behaves as a perfect paramagnet.

“Instead of making a chip that stores 20 gigabytes, you have one that can handle one terabyte, or 50 times more data,” Narayan said.

This material might also open new doors for boosting vehicles’ fuel economy and reducing heat produced by semiconductors, with fuel economy potentially achieving 80 miles per gallon. The process would allow them to develop a new generation of ceramic engines able to withstand twice the temperatures of normal engines.

Narayan said that by using the process of selective doping, the engineers could introduce metallic properties into ceramics.

Selective doping also advances knowledge in the field of spintronics. The nanomaterial was manipulated so the electrons’ spin within the material could be controlled, which could prove valuable to harnessing the electrons’ energy. The ability could be important for engineers working to produce even more efficient semiconductors.

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NASA's Mach 5+ X-43A, first flown on March 27, 2004

NASA’s Aeronautics Research Mission Directorate and the Air Force Research Laboratory’s Office of Scientific Research have tapped the University of Virginia in Charlottesville, Texas A&M University in College Station and Teledyne Scientific & Imaging LLC of Thousand Oaks, Calif. to be the nation’s hypersonic science centers.

The new centers will focus on Mach 5 aircraft using “air-breathing” propulsion. Of special interest to people in the ceramics field is that these centers will be spending a lot of time working on the materials and structures of such aircraft.

“NASA and the Air Force Research Laboratory have made a major commitment to advancing foundational hypersonic research and training the next generation of hypersonic researchers,” said James Pittman, principal investigator for the Hypersonics Project of NASA’s Fundamental Aeronautics Program at NASA’s Langley Research Center in Hampton, Va. “Our joint investment of $30 million over five years will support basic science and applied research that improves our understanding of hypersonic flight.”

Researchers hope to eventually create an engine that could propel aircraft to speeds exceeding 12 times the speed of sound.

Each center will have a different specialty. The UVA center will be the National Center for Hypersonic Combined Cycle Propulsion. Researchers from the University of Pittsburgh, George Washington University, Cornell University, Stanford University, Michigan State University, SUNY Buffalo, North Carolina State University, ATK GASL Inc. (Ronkonkoma, N.Y.), NIST and Boeing will join the UVA effort.

Teledyne Scientific & Imaging will be the National Hypersonic Science Center for Hypersonic Materials and Structures. Team members include researchers from the University of California, University of Colorado in Boulder, the University of Miami, Princeton University, Missouri University of Science and Technology, the University of California, Berkeley and the University of Texas.

Texas A&M’s project, the soon-to-be National Center for Hypersonic Laminar-Turbulent Transition will concentrate in boundary layer control research. It’s partners include researchers from the California Institute of Technology, the University of Arizona, the UCLA and Case Western Reserve University.

In the past, the work by NASA and the AFOSR sometimes overlapped. The announcement about establishing the three centers follows a review of each other’s technology portfolios.

“The Air Force Office of Scientific Research is very excited to continue our partnership with NASA,” said John Schmisseur, manager for the Air Force Office of Scientific Research’s Hypersonics and Turbulence Program. “The centers represent our first effort to sponsor research jointly.”

NASA and the AFOSR will each kick in approximately $15 million to fund the centers at the rate of about $2 million per year per center. The funding can be renewed for up to five years. NASA and AFOSR received more than 60 proposal before selecting UVA, Texas A&M and Teledyne.

Teledyne is clearly pleased with making the cut.

“For over three decades, Teledyne Scientific & Imaging has been a leader in the development of novel materials such as ultra-high performance ceramic composites, polymer composites, and multi-functional materials,” said Robert Mehrabian, chairman, president, and chief executive officer of Teledyne Technologies. “Teledyne is honored by our selection as a National Hypersonic Science Center from an extremely competitive group of respondents. This effort supports Teledyne’s strategy of leadership in areas of fundamental science and technology critical to the U.S. Government.”

According to its abstract, Teledyne says it will lead an effort to “[R]evolutionize the design of hypersonic vehicles by creating a new class of hybrid, hierarchical materials that achieve substantial breakthroughs in oxidation resistance, maximum useable temperature, and maximum supportable heat flux.”

The company says this will cover:

• Novel routes for combining different materials in tailored morphologies,
• New experimental methods that will enable the direct visualization of the mechanisms that control a material’s performance,
• Multi-scale probabilistic model formulations that can simulate mechanisms at all length scales with high fidelity,
• Novel methods of net-shape processing, and
• The combination of experiments and multi-scale models into a virtual test system that will transform the way in which materials are designed and qualified.

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