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There a lot of great stuff going on:
On the absolute temperature scale that is used by physicists, the Kelvin scale, one cannot go below zero—at least not in the sense of getting colder than zero Kelvin. Physicists of the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics, Garching, Germany, have now created an atomic gas in the lab that has nonetheless negative Kelvin values. These negative absolute temperatures lead to several striking consequences: Although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse, a behavior that is also postulated for dark energy in cosmology. Also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100 percent. In order to bring water to the boil, energy needs to be added to the water. During heating up, the water molecules increase their kinetic energy over time and move faster on average. Yet, the individual molecules possess different kinetic energies, from very slow to very fast. In thermal equilibrium, low-energy states are more likely than high-energy states, i.e., only a few particles move really fast. In physics, this distribution is called Boltzmann distribution. Physicists led by Ulrich Schneider and Immanuel Bloch have now created a gas in which this distribution is inverted: Many particles possess large energies and only a few have small energies. This inversion of the energy distribution means that the particles have assumed a negative absolute temperature. “The inverted Boltzmann distribution is the hallmark of negative absolute temperature; and this is what we have achieved,” says Schneider. “Yet the gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature. The temperature scale simply does not end at infinity, but jumps to negative values instead.”
(GizMag) A streetscape that includes natural landscaping, bicycle lanes, wind powered lighting, storm water diversion for irrigation, drought-resistant native plants and innovative concrete has earned Cermak Road in Chicago the title of “Greenest Street in America” according to the Chicago Department of Transport (CDOT). The location runs through an industrial zone which links the state and US highways. The project will record quantifiable results through a set of equally aggressive sustainability goals charting eight performance areas such as storm water management, material reuse, energy reduction, and place making. The most anticipated data will be collected from the first commercial use of photocatalytic cement for the inside highway lanes. This “smog eating” cement contains nano particles of titanium dioxide and is designed to clean the surface of the road and remove nitrogen oxide from the surrounding air through a catalytic reaction driven by UV light. In addition CDOT used 30 percent recycled content in the sidewalk concrete.
Researchers from the University of Pennsylvania have shown a new way to direct the assembly of liquid crystals, generating small features that spontaneously arrange in arrays based on much larger templates. “Liquid crystals naturally produce a pattern of close-packed defects on their surfaces,” says Shu Yang, leader of the study, “but it turns out that this pattern is often not that interesting for device applications. We want to arbitrarily manipulate that pattern on demand.” Electrical fields are often used to change the crystals’ orientation, as in the case with liquid crystal displays, but the Penn research team was interested in manipulating defects by using a physical template. Employing a class of liquid crystals that forms stacks of layers spaced in nanometers—known as “smectic” liquid crystals—the researchers set out to show that, by altering the geometry of the molecules on the bottommost layer, they could produce changes in the patterns of defects on the topmost. “The molecules can feel the geometry of the template, which creates a sort of elastic cue,” says another research, Kathleen Stebe. “That cue is transmitted layer by layer, and the whole system responds.” The researchers’ template was a series of microscopic posts arrayed like a bed of nails. By altering the size, shape, symmetry and spacing of these posts, as well as the thickness of the liquid crystal film, the researchers discovered they could make subtle changes in the patterns of the defects.
(Government Executive) DARPA has developed an injectable foam that shows promise in reducing death from internal bleeding, especially in situations involving noncompressible wounds. Two separate liquid compounds are injected in the body. When the two liquids mix, they react to form a foam coagulant that expands within the abdominal cavity-compressing the wound without sticking to vital organs. In tests, the compression was shown to reduce blood loss by six-fold and increase the three hour survival rate to 72 percent, up from just eight percent. DARPA Wound Stasis program manager Brian Holloway says, “If testing bears out, the foam technology could affect up to 50 percent of potentially survivable battlefield wounds.”
NASA’s decision to buy an inflatable new room for the International Space Station may push the module’s builder—commercial spaceflight company Bigelow Aerospace—one step closer to establishing its own private stations in orbit. Last week, NASA announced that it will pay $17.8 million for the Nevada-based company’s Bigelow Expandable Activity Module (BEAM), which will be affixed to the huge orbiting lab as a technology demonstration.
This has little to do with ceramics or glass—but everything to do with the biggest “What in the world…” moment I have had in a long, long time.” I will try to keep this brief, but its nearly impossible to convey the weird (not meant to be pejorative) materials work of Anna C. Balazs’s team at the University of Pittsburgh.
This all started last week when I breezily was scrolling through a list of new papers published in the recent issue of PNAS. Something in the abstract of “Reconfigurable Assemblies of Active, Autochemotactic Gels” caught my eye. Maybe it was the word “autochemotactic,” which I had to look up. Or, maybe it was these two spooky sentences in the abstract,
“To the best of our knowledge, this is the closest system to the ultimate self-recombining material, which can be divided into separated parts and the parts move autonomously to assemble into a structure resembling the original, uncut sample.… Our findings pave the way for creating reconfigurable materials from self-propelled elements, which autonomously communicate with neighboring units and thereby actively participate in constructing the final structure.”
“Hmm,” I thought. “Wasn’t this the big gimmick in the second Terminator movie?”
Liquid metal or no liquid metal, Balazs had me seriously hooked.
It turns out that Balazs works with Belousov–Zhabotinsky (BZ) gels that are relatively simple and, most importantly, have the fascinating ability to “quiver” for extended periods (but not forever) in predictable patterns by means of a self-regenerating internal redox reaction. Watching how the waves spread through these gels is pretty astounding, but this is no one-trick pony. Balazs and her researchers learned quite a bit about how to manipulate the gels and the oscillations, based on things like shape and composition.
They also learned how to use light on one part of material to stimulate the oscillations to move through the gel from one end towards the other, or use two or more lighted areas to create even more complex oscillations. It turns out that if they made the gel into a cylinder shape, a precise use of the light could actually make the worm slowly move. And, the moves could be complex, with lots of twists and turns in three dimensions, kind of like steering a real worm with sticks, but in this case the sticks are just light beams. But, is this just a good bar trick? Not if you are, say, DARPA, and are looking for a soft, synthetic robot that could climb walls and follow complex routes.
And, Balazs’s group was just warming up. It turns out they also figured out how to make microcapsules of these gels that could emit—in a controllable manner, using light—nanoparticles that create gradients that act in philic or phobic fashions to help propel and steer the capsules, and attract other ones. This is where the self-propulsion, self-recombination and “train” functions starts to come into play. Their models (once they understood the chemistry, most of the group’s work was done through modeling, so lots of video snippets are available) indicated that snake-like assemblies of these capsules could selectively “attract” or drop off other capsules as might be needed.
Okay—I know I am not doing this work justice. But please do me (and yourself) a favor and set a side about 15-30 minutes to watch the above video. The first part features a fairly recent lecture by Balazs (with lots of delightful animations and videos) at Harvard/Radcliffe. You can save yourself some time by starting at about the 2:10 mark.
I know from an unfortunate experience with a family member that sepsis is a helluva medical condition that can arise suddenly, cause enormous pain and, if not diagnosed quickly, can bring unexpected death within a day or two. About 20-35 percent of patients with severe sepsis and 40-60 percent of patients with septic shock die within 30 days. Others die within the ensuing 6 months, often after enduring multiple surgical attempts to identify and treat the source of the infection. According the Centers for Disease Control, sepsis in the United States is the second-leading cause of death in noncoronary ICU patients, and the tenth-most-common cause of death overall. Sepsis is common and also more dangerous in elderly populations.
Thus, I think it is great that DARPA is attempting to take on one of the grand challenges of the medical establishment. The agency describes sepsis as “an overwhelming blood infection, which when coupled with shock (such as that which may be experienced following a combat injury) has a mortality rate near 50 percent. Current methods to identify and treat sepsis may take 48 hours or longer—resulting in increased recovery time from combat wounds and hundreds of preventable deaths.”
Apparently, DARPA began to tackle sepsis beginning in fall 2011 through its Dialysis-Like Therapeutics program. The agency says the goal of the DLT is to demonstrate a portable device capable of quickly sensing and removing bacteria, viruses, toxins and cytokines from the bloodstream on clinically relevant time scales. It notes, “research to date has focused on advancing the components needed for such a device.”
Now it appears that DARPA is taking the next step and has issued a notice requesting “next step” proposals:
DARPA [is] seeking integration of previously awarded DLT projects to develop sensors, complex fluid manipulation architectures, separation technologies and closed-loop control algorithms. After integration, DARPA hopes for a single device capable of removing at least 90 percent of sepsis-causing material from a patient within 24 hours. The DLT device sought by DARPA would differ from kidney dialysis devices by potentially enabling continuous, early sensing based on the entire blood volume, removing the need for anticoagulants, and facilitating label-free separation of multiple targets within the blood.
DLT is a technology demonstration and human trials will not be funded. However, proposers are encouraged to submit plans for testing that would result in an investigational device exemption approval from the Food and Drug Administration (FDA). The FDA will be engaged with the DLT team throughout the program lifecycle by reviewing proposals, participating in proposers’ day meetings and participating in Government review boards.
If successful, the sepsis technology should prevent the deaths of thousands of people in military service and may open the door to novel detection and treatment approaches for other medical maladies. “DLT represents a revolutionary approach in the treatment of blood-borne illness,” says Tim Broderick, DARPA program manager. “If successful, this technology could be used to treat sepsis faster and more effectively, saving lives and reducing treatment costs. In 2009 alone, more than 1,500 active duty Service members were diagnosed with sepsis. DLT may eliminate the need for expensive culture-based identification methods and extended hospital stays. And, as the technology matures, we believe the device could be adapted to diagnose and treat a variety of illnesses.”
Detailed information about the program and requirements for proposals can be found in the Broad Agency Announcement. The proposal due date is July 13, 2012, and DARPA expects that the awards will be issued in October. The manager for this program is Timothy Broderick.
DARPA has issued a notice saying they are seeking proposals related to developing low-temperature processes for the deposition of thin films whose current minimum processing temperatures exceed the maximum temperature substrates of interest to the Department of Defense. From the notice:
Nontraditional performers outside of the materials research/thin film deposition communities in areas such as surface acoustic wave spectroscopy, plasma physics, photochemistry, etc., are highly encouraged to submit proposals to the LoCo program.
Performance of materials, parts, and assemblies (e.g., tribological, optical, electronic and/or thermal) are dictated by interactions between surfaces and the environment, affecting the cost, capability and readiness of DOD systems. A number of known thin-film materials exist that could mitigate these performance limitations when deposited as coatings on substrates of interest to DOD (e.g., crystalline diamond thin film). However, the high bulk deposition temperatures used in state-of-the-art chemical vapor deposition processes to meet the energetic and chemical requirements for processes, such as reactant flux, surface mobility and reaction energy, are often higher than the maximum temperature that many DOD-relevant substrates can withstand (i.e., due to property changes such as melting, grain growth, etc.). These synthetic constraints not only affect our ability to manipulate surfaces of existing DOD systems, but also restrict development of new technologies on emerging substrates (e.g., diamond on polymers for flexible electronics and on living cells for biotic/abiotic interfaces).
To this end, DARPA is seeking innovative multidisciplinary research proposals that independently develop novel chemical and physical processes to meet the energetic/chemical requirements of thin film deposition without reliance on broadband temperature input used in state-of-the-art chemical vapor deposition. DARPA anticipates early stage efforts that address one piece of the deposition puzzle (i.e., process component) such as reactant flux, surface mobility, reaction energy, nucleation, byproduct removal, etc., that will be integrated later in the program to create a full deposition process. The specific objective of the LoCo program is to develop a deposition process applicable to a large variety of thin-film materials. However, to guide proposal development for process components, initial areas of interest for LoCo thin films include synthesis of covalent thin films with long-range order that require high deposition temperatures (>700°C) for insertion points in tribological, thermal management, optical and electronic applications (e.g., crystalline diamond thin films).
The LoCo program is broken into two independent, but intellectually connected thrusts: Thrust 1, the main effort of the LoCo program, is arranged in a progression of discrete tasks that rapidly move from fundamental research to deposition of a thin film on a DOD part for testing and evaluation. Performers will address one or more of the process components for thin film growth (e.g., flux, mobility, reactivity, etc.). This initial effort will focus on validation of the fundamental approach. To facilitate technology transfer, DARPA is also seeking input on DOD systems and parts that could benefit from success in the LoCo program under Thrust 2, where industrial performer team(s) are asked to carry out technical analyses on a proposed DOD part that could benefit from a LoCo coating.
Detailed information about the program and requirements for proposals can be found in the Broad Agency Announcement.
Researchers with unique capabilities looking for teammates or specific expertise should post their in-formation on the teaming site. Proposers are strongly encouraged to submit an abstract in advance of a full proposal. Proposers must submit their abstracts and proposals in response to the DARPA BAA (DARPA-BAA-12-20) through the Grants.gov website or DSO’s BAA website. The proposal abstract due date is June 7, 2012, and the proposal due date is July 26, 2012. The technical contact for this program is: Brian Holloway (DARPA-BAAfirstname.lastname@example.org).
DARPA emphasizes that this notice does not constitute an official solicitation. No information provided here supersedes any of the information in the posted Broad Agency Announcement. This notice does not constitute a specific commitment by DARPA to provide any funds.
Last August DARPA conducted the second test flight of its hypersonic technology vehicle, the Falcon HTV-2. The test ended when the vehicle sent itself into the Pacific Ocean nine minutes into the flight. At the time, the reasons for the abort were unclear and frustrating. The project’s program manager, Maj. Chris Schulz, USAF said then, “We’ll learn. We’ll try again. That’s what it takes.”
To help figure out what it takes, DARPA enlisted the aid of an independent engineering review board comprised of government and academic experts to evaluate the data collected during the flight. The vehicle was built not only to demonstrate the technology, but also as a data-gathering platform. Thus, the ERB had plenty of data telling the story of what happened.
The goal of the program is to develop a vehicle that can reach any location in the world within an hour, which requires hypersonic speeds. According to a story on the DARPA website, the August 11 test flight successfully achieved stable, aerodynamically-controlled speeds up to Mach 20 for the first three minutes. The vehicle appears to have experienced a series of “shockwave disturbances” that were more than 100 times more intense than it was designed to withstand. The vehicle recovered from these first shockwaves and maintained control, which DARPA’s acting director, Kaigham Gabriel observed, was in itself a successful outcome, “That’s a major validation that we’re advancing our understanding of aerodynamic control for hypersonic flight.”
So, how did the vehicle eventually lose control? The ERB conclusion was that “the most probable cause of the HTV-2 Flight 2 premature flight termination was unexpected aeroshell degradation, creating multiple upsets of increasing severity that ultimately activated the Flight Safety System,” which triggered a controlled descent and ocean ditch of the vehicle.
Vehicle design engineers knew there would be a “gradual wearing away of the vehicles skin as it reached stress tolerance limits,” however, more of the vehicle skin separated from the vehicle than was expected. The gaps created by the peeling “created strong, impulsive shock waves around the vehicle,” which caused it to roll suddenly. Eventually, the shockwave-induced rolls became more than the vehicle could overcome.
The old maxim that we learn more from our failures than our successes applies here. Schulz said in the DARPA story, “Data collected during the second test flight revealed new knowledge about thermal-protective material properties and uncertainties for Mach 20 flight inside the atmosphere.” That is, the data collected during the flight showed that the assumptions and extrapolations used to design the vehicle were not enough to predict accurately the extreme environment experienced at Mach 20. Schulz says, “The result of these findings is a profound advancement in understanding the areas we need to focus on to advance aerothermal structures for future hypersonic vehicles. Only actual flight data could have revealed this to us.”
The DARPA story says the next step for the program is to improve models for “characterizing the thermal uncertainties and heat-stress allowances for the vehicle’s outer shell.”
However, accurately characterizing materials at high temperatures is not easy. Last week we summarized a review article on methods for measuring thermophysical properties above 1,500°C, a laboratory capability that is being driven largely by aerospace and nuclear applications. Even the business of accurately measuring temperature for those tests is as much art as science.
These materials are not easy to work with, either. The materials under investigation are refractory nonoxide composites, like C/SiC, sometimes with refractory borides mixed in. The cover story of the January/February issue of The Bulletin gives an overview of materials, processes and properties of UHTC composite materials under investigation for hypersonic vehicles in the UK. In the US, a multi-university and industry partnership is working on the problem under the umbrella organization, National Hypersonic Science Center for Materials and Structures.
A recent paper (abstract only) by a research team at the University of California, Santa Barbara—one of the partner universities—describes a method for measuring strain at high-temperatures. The authors, Mark Novak and Frank Zok, note that development of materials for extreme environments requires the ability to reproduce conditions in the laboratory, which is not trivial.
In their paper, they use digital image correlation to measure displacement and strain. DIC is an optical, non-contact method that can be used at high temperatures.
Displacements are measured by correlating speckle pattern images of specimen surfaces in the deformed state to the undeformed state. Strains are determined by differentiating between displacement fields. The technique eliminates strain gauges, and they report, is accurate with excellent spatial resolution. It has the further advantage of being useful for specimens subject to thermal gradients or mechanical loads because it can recognize out-of-plane displacements.
The trick is in the imaging, which requires an illumination source that can be distinguished from the glow of thermal radiation. Also, heat haze is a problem when the measurements are made in ambient air. Finally, the speckle pattern itself has to be thermally stable and have enough contrast in the test temperature interval.
The paper describes a technique Novak and Zok devised using a CO2 laser as the illumination source, which they demonstrated on a C/SiC composite and a nickel base superalloy (Inconel 625). Alumina or zirconia paints were used to enhance the speckle contrast on the composite; the superalloy was oxidized to create a dark background.
Heat haze was managed by using an “air knife,” which blows air across the surface of the sample, minimizes turbulence and mixes the air in the sight lines of the imaging instruments. The air knife did not completely eliminate heat haze, but their results show that using it led to sharper images and reduced the standard deviation of strain values by a factor of three.
They were able to demonstrate full-field strain mapping up to 1,500°C, and suggest that the upper-temperature limit for measuring thermomechanical properties could be extended by modifying the illumination and filtering out longer wavelengths.