According to a press release, Oak Ridge National Laboratory, via its Center for Nanophase Materials Sciences Division, is developing a chemical and biological sensor with unprecedented sensitivity.

The device consists of a digital camera, a laser, imaging optics, a signal generator, digital signal processing and other components that can detect tiny amounts of substances in the air.

Researchers believe this new “sniffer” will achieve a detection level that approaches the theoretical limit, surpassing other state-of-the-art chemical sensors. The implications could be significant for anyone whose job is to detect explosives, biological agents and narcotics.

“While the research community has been avoiding the nonlinearity associated with the nanoscale mechanical oscillators, we are embracing it,” says codeveloper Nickolay Lavrik, a researcher in the CNMS. “In the end, we hope to have a device capable of detecting incredibly small amounts of explosives compared to today’s chemical sensors.”

The approach makes use of microcantilevers similar to those used in atomic force microscopy. The microcanilevers serve as microresonators that measure changes in the resonance frequency due to mass changes. Although the concept is relatively simple, assembling a working model is more difficult.

“These challenges are due to requirements of measuring and analyzing tiny oscillation amplitudes that are about the size of a hydrogen atom,” Lavrik reports. He says previous approaches would have required sophisticated low-noise electronic components such as lock-in amplifiers and phase-locked loops, which add cost and complexity.

This new type of sniffer works by deliberately hitting the microcantilevers with relatively large amounts of energy associated with a range of frequencies, forcing them into wide oscillation.

“In the past, people wanted to avoid this high amplitude because of the high distortion associated with that type of response,” says ORNL’s Panos Datskos, a member of the Measurement Science and Systems Engineering Division. “But now we can exploit that response by tuning the system to a very specific frequency that is associated with the specific chemical or compound we want to detect.”

When the target chemical reacts with the microcantilever, it shifts the frequency depending on the weight of the compound, thereby providing the detection.

“With this new approach, when the microcantilever stops oscillating we know with high certainty that the target chemical or compound is present,” Lavrik says.

The researchers envision this technology being incorporated in a handheld instrument that could be used by transportation security screeners, law enforcement officials and the military. Other potential applications are in biomedicine, environmental science, homeland security and analytical chemistry.

The Daily Northwestern reported that Northwestern University received $2.4 million in government funding to develop flash-memory devices with enhanced capacity for U.S. military and intelligence use.

Allocated to NU’s Center for Integrated Nanosystems and International Institute for Nanotechnology, the money represents “substantial and welcome funding” for the field of nanoelectronics, says Fraser Stoddart, CINS director and NU Board of Trustees professor of chemistry.

The funding is part of $45.4 million for Illinois-based projects approved by Congress on Dec. 19 in a 2010 defense spending bill, according to the a news release on Sen. Dick Durbin’s (D-Il) web site.

Developing memory chips will involve building and mounting mechanical switches into infinitely stretching three-dimensional scaffolds on the molecular level, he said.

“Over 10 years ago, we developed two-dimensional switches, and this piece of research will put what we did with two into three (dimensions),” Stoddart continues. “If we managed to do this, it would create very dense flash memory.”

Although funded by the Defense Department, the technology will not be limited to surveillance and battlefield operations but could be used to increase the capacity of any flash memory device, he said.

Credit: Ole Kils

I’m blogging now from ACerS’ Electronic Materials and Applications conference in Orlando, where it is a pleasant 70 degrees. Next week I shift over a few miles to Daytona Beach for the ACerS’ ICACC’10 conference.

Yesterday’s keynote speaker was John Blottman from the Office of Naval Research Naval Undersea Warfare Center. Blottman is a mechanical engineer who works on sensors and sonar systems development with the ONR’s Undersea Warfare Center. He is working with a diverse team of engineers and biologist in a Multi-University Research Initiative team that includes academic institutions, federal labs, DoD labs and private-sector support.

Blottman had some interesting concepts to share, not the least of which is that there is a big difference between biomimicry and bioinspiration. The former tries to duplicate nature; the latter uses insights from nature as a starting point to build upon.

While not a biologist, he became interested in the topic a few years ago when the Navy made the development of autonomous, independent systems a priority. Think sonar buoys that might never have to be repaired, refueled or moved by an external force.

He noted that when you look at animal species, you can break their activities down into several biomechanical and biosensory subcategories such as propulsion, energy gathering, self awareness (and self preservation), location sensing, texture sensing, communications with other animal life, and so on.

After looking at several species, Blottman and his colleagues became intrigued with jellyfish, an animal that has been around for millions of years that has relatively primitive but effective motor and sensory abilities, and has a remarkable talent to adapt itself to nearly every water environment. Intrigued may not fully convey how much Blottman and his group are into jellyfish – he was proudly sporting his cool jellyfish tie during the conference.

Using a variety of electronics, smart materials, polymers, piezos and other off-the-shelf materials, some prototype jellyfish-like propulsion contraptions have been successfully tested. While these are still relatively crude, they provide an important proof-of-concept that is providing encouragement for further work.

I hope to have a video of his lecture and a short interview with Blottman in the next few weeks.

Credit: Int'l. Journal of Applied Ceramic Technology

The online version of ACerS’ International Journal of Applied Ceramic Technology has a new story that reveals many of the problems scientists and engineers face when designing the tips of missiles – called domes – used by primarily by the military, and the results of some interesting research on a new dome material. The gist of the paper in ACT is that a group of Saint-Gobain researchers have found that ultra pure α-alumina powder may provide a superior material for making these domes.

Consider, however, the problems that must be addressed in coming up with a dome material. Besides providing an aerodynamic leading surface for air-to-air and air-to-ground missiles, a missile dome shields an array of sensors that control various systems within the missile. Among other things, some of these sensors are used to detect a variety of electromagnetic radiation (e.g., in both visible and infrared ranges).

The best systems must be able to differentiate, for example, between the signature of the exhaust of a jet engine and the signature of decoy flares that a targeted airplane might jettison. Thus the domes have to be functionally transparent in a fairly wide range of the spectrum. Likewise, the shape and thickness of the domes must be such that they don’t distort any of the incoming electromagnetic radiation.

To complicate things even further, the dome must be able to withstand enormous mechanical stresses and thermal shocks. At the start of a missile launch, friction causes the outside leading surface of the front most portion of the dome to heat more rapidly than the rest. This hot front surface expands more than the cooler internal portions of the doom, and soon there is significant stress between the expanded and the unexpanded material. If the stress exceeds the mechanical strength of the material, the dome shatters.

Some materials work well at lower speeds, but new missiles will soon be rocketing at +Mach 4 levels.

Cost and ability to manufacture/machine are factors, too.

A commonly used material for domes is monocrystalline alumina (i.e., sapphire) and polycrystalline magnesium fluoride. Sapphire is costly, difficult to shape and prone to chipping. Large boules of sapphire must be drawn and then machined, which is an art in itself. A sapphire dome that has all of the required properties is typically 4-5 mm thick. The benefit of sapphire is that is a relative transparent material in the 0.25–5 μm range. However, transparency declines significantly at wavelengths higher than 5 μm.

The transparency of MgF₂ is more limited than sapphire, but does very well in the 2–5 μm range, It is much less expensive than sapphire. Unfortunately, MgF₂ isn’t a particularly rugged material.

So, the question is this: Is there some alternative material with good mechanical/thermo-mechanical strength and transparent in the key IR and visible ranges that is easy to work with and cheaper than sapphire, and a thermal shock resistance better than magnesium fluoride will be of use for this kind of application?

Guillaume Bernard-Granger, Christian Guizard and Nathalie Monchalin, from Saint-Gobain’s Laboratoire de Synthèse et Fonctionnalisation des Céramiques, say domes made of a dense and submicronic form α-alumina powder may be a good and relatively inexpensive alternative.

Comparative thermal shock resistance. Credit: Int'l. Journal of Applied Ceramic Technology

In brief, they were able to document that their alumina material has good transparency in the visible and mid-infrared ranges and can be formed using mold-and-sintering processes rather than complex and delicate machining. Just as importantly, a dome can be made with a thickness as low as 1 mm and still survive Mach 4 speeds.

Overall, this is just a great example of how advanced ceramics, using ultrapure feedstock refined at the submicron and nano levels is providing new, customizable solutions to engineering problems. Read the paper for the details.

Dye-sensitized nanowires cover the outer surface of a optical fiber to optimize photon collection. (Credit: Angewandte Chemie International.)

What if there was a way to create a material covered with tiny three-dimensional solar collectors instead of the typical 2D flat photovoltaic systems (and in this context flexible PV sheets still count as two-dimensional)? And, what if you could “feed” these collectors with sunlight via optical fibers? Then you might be able to tuck these systems (architecturally speaking) into out-of-the-way locations or sites less obvious than rooftops.

That was some of the thinking motivating a group of researchers at Georgia Tech whose work is reported on in a new paper in Angewandte Chemie International.

The GT group figured out a way to improve upon existing dye-sensitized solar cell technology by growing nanostructures (on the optical fibers) that effectively increase the surface area of a collector. Compared to other approaches, DSSCs, generally speaking, are at a disadvantage because they relatively inefficient. On the other hand, the manufacturing costs of dye-sensitized cells are low. They also tend to be able to take more mechanical abuse.

The group grows the nanostructures by replacing in one section the outer layer of quartz optical fiber with a conductive coating. They then seed the surface with zinc oxide followed by solution-based techniques that grow aligned zinc oxide nanowires that radiate outward around the fiber. Finally, the nanowire–optical fiber is given a dye-sensitized materials coating. Groups of these nanowire-coated fibers are immersed in an electrolyte to harvest electrons. Length improves efficiency and the group has been able to make nanowire sections as long as 20 cm.

Closeup of single nanowire-coated fiber. (Credit: Georgia Tech and Gary Meek.)

According the the GT group, this internal axial illumination in this hybrid system multiplies six-fold the energy conversion efficiency of the DSSC nanowire array. “In each reflection within the fiber, the light has the opportunity to interact with the nanostructures that are coated with the dye molecules,” explains Z.L. Wang, who led the group. “You have multiple light reflections within the fiber, and multiple reflections within the nanostructures. These interactions increase the likelihood that the light will interact with the dye molecules, and that increases the efficiency.”

The team says it has reached an efficiency of 3.3 percent and think efficiencies of 7 to 8 percent are in reach if they make further modifications, such as using a better method for collecting the charges and a titanium oxide surface coating.

These efficiencies are still a long way off of current 2D PV units. But Wang says there would be several advantages to the group’s hybrid DSSC system. The already low production cost could be driven lower by using polymer fibers. The optical fibers used to feed the nanowire fibers could be placed fairly freely, providing a larger area for gathering light, and lenses could also be employed to focus the incoming light.

Another advantage is that it gives building designers new options. “This will really provide some new options for photovoltaic systems,” Wang said. “We could eliminate the aesthetic issues of PV arrays on building. We can also envision PV systems for providing energy to parked vehicles, and for charging mobile military equipment where traditional arrays aren’t practical or you wouldn’t want to use them.”