Conventional superhydrophobic coatings that repel liquids by trapping air inside microscopic surface pockets tend to lose their properties when liquids are forced into those pockets. In this work ("Collapse and Reversibility of the Superhydrophobic State on Nanotextured Surfaces"), extremely water-repellant or superhydrophobic surfaces were fabricated that can withstand pressures that are 10 times greater than the average pressure a surface would experience resting in a room. The surfaces resist the infiltration of liquid into the nanoscale pockets. 
(Top left) Arrays of tapered-cone and (bottom left) cylindrical nanostructures that create superhydrophobic or water-repellant surfaces. Air pockets between the structures give rise to the hydrophobic properties. (Right) High-speed photographs of a falling water droplet on a nanostructured surface (top) before, (middle) during, and (bottom) after impact. The extent to which nanometer-size textured, superhydrophobic coatings can withstand elevated pressures is largely determined by the geometry of the texturing. This work shows that by careful tuning of the nanoscale geometry, substantial gains in the durability and applicability of these structures for solar panels, highly robust, self-healing coatings, and anti-icing applications could be realized. Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. However, the resulting composite interface is prone to collapse under external pressure. Nanometer-size textures should facilitate more resilient coatings owing to geometry and confinement effects at the nanoscale. This study uses in situ x-ray diffraction to investigate the extent to which the superhydrophobic state in arrays of ~20 nanometer-wide silicon textures with cylindrical, conical, and linear features persists under pressure. The research revealed that the upper bounds of the superhydrophobic state are reached when the liquid pressure is raised above a critical value, which depends on texture shape and size. This infiltration is modeled quantitatively by accounting for the actual geometry of the texture and macroscopic capillary theory. Another important finding is that the infiltration is irreversible for all but the conical surface textures, which exhibit a spontaneous, partial reappearance of the trapped gas phase upon liquid depressurization. This phenomenon appears to be influenced by the kinetics of gas-liquid exchange. These results have profound implications for the understanding and the design of nanosized multiphase (liquid/vapor) systems, including more effective superhydrophobic coatings.
read more "Super water-repellant nanocoatings can now take the pressure"
(Top left) Arrays of tapered-cone and (bottom left) cylindrical nanostructures that create superhydrophobic or water-repellant surfaces. Air pockets between the structures give rise to the hydrophobic properties. (Right) High-speed photographs of a falling water droplet on a nanostructured surface (top) before, (middle) during, and (bottom) after impact. The extent to which nanometer-size textured, superhydrophobic coatings can withstand elevated pressures is largely determined by the geometry of the texturing. This work shows that by careful tuning of the nanoscale geometry, substantial gains in the durability and applicability of these structures for solar panels, highly robust, self-healing coatings, and anti-icing applications could be realized. Superhydrophobic coatings repel liquids by trapping air inside microscopic surface textures. However, the resulting composite interface is prone to collapse under external pressure. Nanometer-size textures should facilitate more resilient coatings owing to geometry and confinement effects at the nanoscale. This study uses in situ x-ray diffraction to investigate the extent to which the superhydrophobic state in arrays of ~20 nanometer-wide silicon textures with cylindrical, conical, and linear features persists under pressure. The research revealed that the upper bounds of the superhydrophobic state are reached when the liquid pressure is raised above a critical value, which depends on texture shape and size. This infiltration is modeled quantitatively by accounting for the actual geometry of the texture and macroscopic capillary theory. Another important finding is that the infiltration is irreversible for all but the conical surface textures, which exhibit a spontaneous, partial reappearance of the trapped gas phase upon liquid depressurization. This phenomenon appears to be influenced by the kinetics of gas-liquid exchange. These results have profound implications for the understanding and the design of nanosized multiphase (liquid/vapor) systems, including more effective superhydrophobic coatings.
(Image: Chan Lei and Keith Schwab/Caltech) Researchers have known for years that in classical physics, physical objects indeed can be motionless. Drop a ball into a bowl, and it will roll back and forth a few times. Eventually, however, this motion will be overcome by other forces (such as gravity and friction), and the ball will come to a stop at the bottom of the bowl. "In the past couple of years, my group and a couple of other groups around the world have learned how to cool the motion of a small micrometer-scale object to produce this state at the bottom, or the quantum ground state," says Keith Schwab, a Caltech professor of applied physics, who led the study. "But we know that even at the quantum ground state, at zero-temperature, very small amplitude fluctuations—or noise—remain." Because this quantum motion, or noise, is theoretically an intrinsic part of the motion of all objects, Schwab and his colleagues designed a device that would allow them to observe this noise and then manipulate it. The micrometer-scale device consists of a flexible aluminum plate that sits atop a silicon substrate. The plate is coupled to a superconducting electrical circuit as the plate vibrates at a rate of 3.5 million times per second. According to the laws of classical mechanics, the vibrating structures eventually will come to a complete rest if cooled to the ground state. But that is not what Schwab and his colleagues observed when they actually cooled the spring to the ground state in their experiments. Instead, the residual energy—quantum noise—remained. "This energy is part of the quantum description of nature—you just can't get it out," says Schwab. "We all know quantum mechanics explains precisely why electrons behave weirdly. Here, we're applying quantum physics to something that is relatively big, a device that you can see under an optical microscope, and we're seeing the quantum effects in a trillion atoms instead of just one." Because this noisy quantum motion is always present and cannot be removed, it places a fundamental limit on how precisely one can measure the position of an object. But that limit, Schwab and his colleagues discovered, is not insurmountable. The researchers and collaborators developed a technique to manipulate the inherent quantum noise and found that it is possible to reduce it periodically. Coauthors Aashish Clerk from McGill University and Florian Marquardt from the Max Planck Institute for the Science of Light proposed a novel method to control the quantum noise, which was expected to reduce it periodically. This technique was then implemented on a micron-scale mechanical device in Schwab's low-temperature laboratory at Caltech. "There are two main variables that describe the noise or movement," Schwab explains. "We showed that we can actually make the fluctuations of one of the variables smaller—at the expense of making the quantum fluctuations of the other variable larger. That is what's called a quantum squeezed state; we squeezed the noise down in one place, but because of the squeezing, the noise has to squirt out in other places. But as long as those more noisy places aren't where you're obtaining a measurement, it doesn't matter." The ability to control quantum noise could one day be used to improve the precision of very sensitive measurements, such as those obtained by LIGO, the Laser Interferometry Gravitational-wave Observatory, a Caltech-and-MIT-led project searching for signs of gravitational waves, ripples in the fabric of space-time. "We've been thinking a lot about using these methods to detect gravitational waves from pulsars—incredibly dense stars that are the mass of our sun compressed into a 10 km radius and spin at 10 to 100 times a second," Schwab says. "In the 1970s, Kip Thorne [Caltech's Richard P. Feynman Professor of Theoretical Physics, Emeritus] and others wrote papers saying that these pulsars should be emitting gravity waves that are nearly perfectly periodic, so we're thinking hard about how to use these techniques on a gram-scale object to reduce quantum noise in detectors, thus increasing the sensitivity to pick up on those gravity waves," Schwab says. In order to do that, the current device would have to be scaled up. "Our work aims to detect quantum mechanics at bigger and bigger scales, and one day, our hope is that this will eventually start touching on something as big as gravitational waves," he says.
Schematic showing a new engineered surface that can repel liquids in any state of wetness. “This represents a fundamentally new concept in engineered surfaces,” said Tak-Sing Wong, assistant professor of mechanical engineering and a faculty member in the Penn State Materials Research Institute. “Our surfaces combine the unique surface architectures of lotus leaves and pitcher plants, in such a way that these surfaces possess both high surface area and a slippery interface to enhance droplet collection and mobility. Mobility of liquid droplets on rough surfaces is highly dependent on how the liquid wets the surface. We have demonstrated for the first time experimentally that liquid droplets can be highly mobile when in the Wenzel state.” Liquid droplets on rough surfaces come in one of two states, Cassie, in which the liquid partially floats on a layer of air or gas, and Wenzel, in which the droplets are in full contact with the surface, trapping or pinning them. The Wenzel equation was published in 1936 in one of the most highly cited papers in the field; yet until now, it has been extremely challenging to precisely verify the equation experimentally. “Through careful, systematic analysis, we found that the Wenzel equation does not apply for highly wetting liquids,” said Birgitt Boschitsch Stogin, a graduate student in Wong’s group and coauthor on a paper titled “Slippery Wenzel State”, published in the August 28 online edition of the journal . “Droplets on conventional rough surfaces are mobile in the Cassie state and pinned in the Wenzel state. The sticky Wenzel state results in many problems in condensation heat transfer, water harvesting and ice removal. Our idea is to solve these problems by enabling Wenzel state droplets to be mobile,” said Xianming Dai, a postdoctoral scholar in Wong’s group and the lead author on the paper. 
In conventional superhydrophobic rough surfaces, tiny liquid droplets in the Wenzel state will remain pinned to the surface textures. In contrast, the new slippery rough surface enables high mobility for Wenzel droplets. In the last decade, tremendous efforts have been devoted to designing rough surfaces that prevent the Cassie-to-Wenzel wetting transition. A key conceptual advance in the current study is that both Cassie and Wenzel state droplets can retain mobility on the slippery rough surface, foregoing the difficult process of preventing the wetting transition. In order to make Wenzel state droplets mobile, the researchers etched micrometer scale pillars into a silicon surface using photolithography and deep reactive-ion etching, and then created nanoscale textures on the pillars by wet etching. They then infused the nanotextures with a layer of lubricant that completely coated the nanostructures, resulting in greatly reduced pinning of the droplets. The nanostructures also greatly enhanced lubricant retention compared to the microstructured surface alone. The same design principle can be easily extended to other materials beyond silicon, such as metals, glass, ceramics and plastics. The authors believe this work will open the search for a new, unified model of wetting physics that explains wetting phenomena on rough surfaces such as theirs.
Fig.1: Momentum dependence of excitation energy. Black dots: Energy of acoustic mode obtained from IXS experiments. Dashed line (blue): The energy of the acoustic mode given by the chain model shown in Fig. 2(a). Solid line (red): The energy of the acoustic mode given by the chain model shown in Fig. 2(b) (Image: M. Inui, Graduate School of Integrated Arts and Sciences, Hiroshima University, et al.) Studies of the atomic dynamics in liquid Bi have been revisited more recently. The previous inelastic neutron scattering (INS) results for liquid Bi showed inconsistency for the inelastic excitation of the acoustic mode. These results were also different from the ab initio molecular dynamics (AIMD) prediction that indicated that the peculiar atomic dynamics arose from an anisotropic interatomic force in this monatomic liquid (J. Souto et al., 81, 134201 (2010)). Therefore, it is important to observe the inelastic excitation of the acoustic mode in liquid Bi using inelastic x-ray scattering (IXS). Professor M. Inui at Hiroshima University and his collaborators at Kumamoto University, Keio University, SPring-8/JASRI, and the RIKEN SPring-8 Center measured the IXS on liquid Bi at SPring-8 (A.Q.R Baron et al., , 61, 461 (2000)). This research group found that the dispersion curve of the excitation energy of the acoustic mode exhibits a flat region as a function of the momentum transfer. 
Fig.2: Analytical model. (a) One-dimensional chain where atoms are connected by springs with the same force constant. (b) One-dimensional chain where n atomic pairs connected by a strong spring are connected by weak springs. (Image: M. Inui, Graduate School of Integrated Arts and Sciences, Hiroshima University, et al.) The experiments conducted by Professor Inui et al. used a single-crystal sapphire cell of the Tamura type that was carefully machined to provide a 0.04-mm sample thickness. It is said that only his research group can make full use of this “world-famous” cell, which was used to stably conduct an x-ray beam experiment under high temperatures. Furthermore, this research group reported that the IXS experimental results for liquid Bi clearly show a distinct inelastic excitation of the acoustic mode. This resolves the previous disagreement in the literature. Those researchers said, “Consistent with ab initio calculations of liquid Bi, the dispersion curve was nearly flat from 7 to 15 nm [to the negative 1 power].” 
Fig.3: Structure of crystalline bismuth. Schematic picture using simple cubic lattice, where bold and broken lines denote short strong bonds and long weak ones, respectively. (Image: M. Inui, Graduate School of Integrated Arts and Sciences, Hiroshima University, et al.) They also mentioned, “A long-range force is needed to reproduce the flatness of the dispersion curve, and the long-range force has to strongly be related to a local structure consisting of shorter and longer bounds in the liquid.” This research group demonstrated a possible mechanism for the unusual dispersion of liquid Bi. Their results will greatly contribute to the development of nanotechnology.
Conventional superconductors only achieve their zero-resistance state at close to absolute zero. A better understanding of the physical mechanisms responsible for the binding of electron pairs that gives rise to superconductivity could lead to the discovery of room-temperature superconductors. Superconductors conduct electricity with zero resistance, and hence they could potentially revolutionize electric motors, generators and utility grids. However, scientists have yet to discover a material that becomes superconducting at ambient temperature—all known superconductors operate only at cryogenic temperatures, making them impractical for general applications. Unfortunately, progress toward achieving the goal of room-temperature superconductivity has been hindered by scientists’ limited understanding of the fundamental mechanism responsible for the emergence of this remarkable physical phenomenon. Superconductivity occurs as the result of pairs of electrons binding together in such a way that they act as a single quasiparticle. In conventional superconductors, which include elemental materials that become superconducting at temperatures very close to absolute zero, the binding force is provided by vibrations in the atomic lattice through which the electrons travel. Yet not all superconductors behave this way. In unconventional superconductors that do not fit the conventional model, this binding force develops in a different manner and various mechanisms have been proposed for it. One such mechanism is the magnetic or spin fluctuation of the electrons themselves, which binds electrons in pairs through the entanglement of electron spins. However, recent experiments have shown that this mechanism cannot explain the superconducting state in the quintessential unconventional superconductor CeCu
A polaron (blue) is a particle such as an electron that moves through and interacts with a material. Polarons interact with atomic vibrations (phonons) in a ‘phonon bath’ (gridlines) defined by the crystal structure. (Image: Naoto Nagaosa, RIKEN Center for Emergent Matter Science) The movement of electrons in crystals is one of the defining characteristics of materials and determines their behavior in many practical applications. As electrons move through a crystal, they interact with surrounding atoms via atomic vibrations known as phonons. A particle moving in such a ‘phonon bath’ is known as a polaron (Fig. 1). “Polarons occur in almost every transport phenomenon in solids,” explains Nagaosa. Despite their ubiquity, however, deriving a mathematical description of polarons has proved a challenge that has confounded even some of our most famous physicists. The problem is the difficulty of reducing the complexity of interactions that make up a polaron to a few basic simplifications. Although this strategy works well for many problems in physics, phonon systems are so complex they defy simplification. Consequently, previous approaches have been limited to approximations only. In contrast, Nagaosa and his colleagues used mathematically exact computational methods without approximations to calculate results for specific scenarios. They then mapped the information gained from these calculations onto a two-dimensional ‘phase diagram’ of temperature versus strength of interaction between the electron and the surrounding phonon bath. The phase diagram revealed a strong dependence of polaron transport on temperature and strength of interaction, with several distinct transport regimes that explain many of the observed fundamental properties of materials, such as the electrical conductivity of metals and semiconductors. “The study of polarons and particularly polaron mobility is important for technology because polarons are carriers in many modern electronic devices,” says Mishchenko. Although derived in general terms, the researchers’ calculations and the resultant phase diagram are so far limited to describing polarons in one dimension. Extending the theory to higher dimensions will allow a more realistic description of polaron behavior and could lead to a fundamental model that describes a broad range of important effects in materials, such as magnetism and superconductivity.
Graphene nanoribbon under the microscope. (Image: University of Basel) Graphene is one of the most promising materials for improving electronic devices. The two-dimensional carbon sheet exhibits high electron mobility and accordingly has excellent conductivity. Other than usual semiconductors, the material lacks the so-called band gap, an energy range in a solid where no electron states can exist. Therefore, it avoids a situation in which the device is electronically switched off. However, in order to fabricate efficient electronic switches from graphene, it is necessary that the material can be switched ”on” and ”off”. The solution to this problem lies in trimming the graphene sheet to a ribbon-like shape, named graphene nanoribbon (GNR). Thereby it can be altered to have a band gap whose value is dependent on the width of the shape. Synthesis on Gold Surface To tune the band gap in order for the graphene nanoribbons to act like a well-established silicon semiconductor, the ribbons are being doped. To that end, the researchers intentionally introduce impurities into pure material for the purpose of modulating its electrical properties. While nitrogen doping has been realized, boron-doping has remained unexplored. Subsequently, the electronic and chemical properties have stayed unclear thus far. Prof. Dr. Ernst Meyer and Dr. Shigeki Kawai from the Department of Physics at the University of Basel, assisted by researchers from Japanese and Finnish Universities, have succeeded in synthesizing boron-doped graphene nanoribbons with various widths. They used an on-surface chemical reaction with a newly synthesized precursor molecule on an atomically clean gold surface. The chemical structures were directly resolved by state-of-the-art atomic force microscopy at low temperature. Towards a Nitrogen Oxide-Sensor The doped site of the boron atom was unambiguously confirmed and its doping ratio – the number of boron atoms relative to the total number of atoms within the nanoribbon – lay at 4.8 atomic percent. By dosing nitric oxide gas, the chemical property known as the Lewis acidity could also be confirmed. The doped nitric oxide gas was highly-selectively adsorbed on the boron site. This measurement indicates that the boron-doped graphene nanoribbon can be used for an ultra-high sensitive gas sensor for nitrogen oxides which are currently a hot topic in the industry as being highly damaging to the environment.
Moore’s law still holds true after 50 years. (Image: shigeru23, CC BY-SA) (click on image to enlarge) Nevertheless, silicon electronics faces a challenge: the latest circuits measure just 7nm wide – between a red blood cell (7,500nm) and a single strand of DNA (2.5nm). The size of individual silicon atoms (around 0.2nm) would be a hard physical limit (with circuits one atom wide), but its behaviour becomes unstable and difficult to control before then. Without the ability to shrink ICs further silicon cannot continue producing the gains it has so far. Meeting this challenge may require rethinking how we manufacture devices, or even whether we need an alternative to silicon itself. Speed, heat, and light To understand the challenge, we must look at why silicon became the material of choice for electronics. While it has many points in its favour – abundant, relatively easy to process, has good physical properties and possesses a stable native oxide (SiO
Semiconductor lasers, where alternatives to silicon such as germanium have already found a role. (Image: CC BY-SA) New materials for future Of the many materials under investigation as partners for silicon to improve its electronic performance, perhaps three have promise in the short term. The first concerns silicon’s poor electron hole mobility. A small amount of germanium is already added to improve this, but using large amounts or even a move to all-germanium transistors would be better still. Germanium was the first material used for semiconductor devices, so really this is a “back to the future” move. But re-aligning the established industry around germanium would be quite a problem for manufacturers. The second concerns metal oxides. Silicon dioxide was used within transistors for many years, but with miniaturisation the layer of silicon dioxide has shrunk to be so thin that it has begun to lose its insulating properties, leading to unreliable transistors. Despite a move to using rare-earth hafnium dioxide (HfO2) as a replacement insulator, the search is on for alternatives with even better insulating properties. Most interesting, perhaps, is the use of so-called III-V compound semiconductors, particularly those containing indium such as indium arsenide and indium antimonide. These semiconductors have electron mobility up to 50 times higher than silicon. When combined with germanium-rich transistors, this approach could provide a major speed increase. Yet all is not as simple as it seems. Silicon, germanium, oxides and the III-V materials are crystalline structures that depend on the integrity of the crystal for their properties. We cannot simply throw them together with silicon and get the best of both. Dealing with this problem, crystal lattice mismatch, is the major ongoing technological challenge. Different flavours of silicon Despite its limitations, silicon electronics has proved adaptable, able to be fashioned into reliable, mass market devices available at minimal cost. So despite headlines about the “end of silicon” or the spectacular (and sometimes rather unrealistic) promise of alternative materials, silicon is still king and, backed by a huge and extremely well-developed global industry, will not be deposed in our lifetime. Instead progress in electronics will come from improving silicon by integrating other materials. Companies like IBM and Intel and university labs worldwide have poured time and effort into this challenge, and the results are promising: a hybrid approach that blends III-V materials, silicon and germanium could reach the market within a few years. Compound semiconductors have already found important uses in lasers, LED lighting/displays and solar panels where silicon simply cannot compete. More advanced compounds will be needed as electronic devices become progressively smaller and lower powered and also for high-power electronics where their characteristics are a significant improvement upon silicon’s capabilities. The future of electronics is bright, and it’s still going to be largely based on silicon – but now that silicon comes in many different flavours.
Dr. Miroshnichenko with his visualization of anapoles as dark matter. The fundamental new theory could be used in quantum computers, lead to new laser technology and may even hold the key to understanding how matter itself hangs together. "Ever since the beginning of quantum mechanics people have been looking for a configuration which could explain the stability of atoms and why orbiting electrons do not radiate," Dr Miroshnichenko said. The absence of radiation is the result of the current being divided between two different components, a conventional electric dipole and a toroidal dipole (associated with poloidal current configuration), which produce identical fields at a distance. If these two configurations are out of phase then the radiation will be cancelled out, even though the electromagnetic fields are non-zero in the area close to the currents. Dr Miroshnichenko, in collaboration with colleagues from Germany and Singapore, successfully tested his new theory with a single silicon nanodiscs between 160 and 310 nanometres in diameter and 50 nanometres high, which he was able to make effectively invisible by cancelling the disc's scattering of visible light. This type of excitation is known as an anapole (from the Greek, 'without poles'). Dr Miroshnichenko's insight came while trying to reconcile differences between two different mathematical descriptions of radiation; one based on Cartesian multipoles and the other on vector spherical harmonics used in a Mie basis set. "The two gave different answers, and they shouldn't. Eventually we realised the Cartesian description was missing the toroidal components," Dr Miroshnichenko said. "We realised that these toroidal components were not just a correction, they could be a very significant factor." Dr Miroshnichenko said the confined energy of anapoles could be important in the development of tiny lasers on the surface of materials, called spasers, and also in the creation of efficient X-ray lasers by high-order harmonic generation.
3-D-printed microfish contain functional nanoparticles that enable them to be self-propelled, chemically powered and magnetically steered. The microfish are also capable of removing and sensing toxins. (Illustration: J. Warner, UC San Diego Jacobs School of Engineering) The research, led by Professors Shaochen Chen and Joseph Wang of the NanoEngineering Department at the UC San Diego, was published in the Aug. 12 issue of the journal ("3D-Printed Artificial Microfish"). By combining Chen's 3D printing technology with Wang's expertise in microrobots, the team was able to custom-build microfish that can do more than simply swim around when placed in a solution containing hydrogen peroxide. Nanoengineers were able to easily add functional nanoparticles into certain parts of the microfish bodies. They installed platinum nanoparticles in the tails, which react with hydrogen peroxide to propel the microfish forward, and magnetic iron oxide nanoparticles in the heads, which allowed them to be steered with magnets. "We have developed an entirely new method to engineer nature-inspired microscopic swimmers that have complex geometric structures and are smaller than the width of a human hair. With this method, we can easily integrate different functions inside these tiny robotic swimmers for a broad spectrum of applications," said the co-first author Wei Zhu, a nanoengineering Ph.D. student in Chen's research group at the Jacobs School of Engineering at UC San Diego. As a proof-of-concept demonstration, the researchers incorporated toxin-neutralizing nanoparticles throughout the bodies of the microfish. Specifically, the researchers mixed in polydiacetylene (PDA) nanoparticles, which capture harmful pore-forming toxins such as the ones found in bee venom. The researchers noted that the powerful swimming of the microfish in solution greatly enhanced their ability to clean up toxins. When the PDA nanoparticles bind with toxin molecules, they become fluorescent and emit red-colored light. The team was able to monitor the detoxification ability of the microfish by the intensity of their red glow. "The neat thing about this experiment is that it shows how the microfish can doubly serve as detoxification systems and as toxin sensors," said Zhu. "Another exciting possibility we could explore is to encapsulate medicines inside the microfish and use them for directed drug delivery," said Jinxing Li, the other co-first author of the study and a nanoengineering Ph.D. student in Wang's research group. How this new 3D printing technology works The new microfish fabrication method is based on a rapid, high-resolution 3D printing technology called microscale continuous optical printing (µCOP), which was developed in Chen's lab. Some of the benefits of the µCOP technology are speed, scalability, precision and flexibility. Within seconds, the researchers can print an array containing hundreds of microfish, each measuring 120 microns long and 30 microns thick. This process also does not require the use of harsh chemicals. Because the µCOP technology is digitized, the researchers could easily experiment with different designs for their microfish, including shark and manta ray shapes. "With our 3D printing technology, we are not limited to just fish shapes. We can rapidly build microrobots inspired by other biological organisms such as birds," said Zhu. The key component of the µCOP technology is a digital micromirror array device (DMD) chip, which contains approximately two million micromirrors. Each micromirror is individually controlled to project UV light in the desired pattern (in this case, a fish shape) onto a photosensitive material, which solidifies upon exposure to UV light. The microfish are built using a photosensitive material and are constructed one layer at a time, allowing each set of functional nanoparticles to be "printed" into specific parts of the fish bodies. "This method has made it easier for us to test different designs for these microrobots and to test different nanoparticles to insert new functional elements into these tiny structures. It's my personal hope to further this research to eventually develop surgical microrobots that operate safer and with more precision," said Li.
Experimental setup used to investigate the directional excitation of surface plasmon polaritons in a one-dimensional gold grating. The probe of a scanning tunneling microscope is used to excite a surface plasmon polariton and the resulting light is analyzed by an inverted optical microscope. Joel Yang and Zhaogang Dong at the A*STAR Institute of Materials Research and Engineering, together with colleagues at the A*STAR Institute of High Performance Computing and other institutes in Singapore, investigated controlling the traveling direction of plasmons in a gold grating both theoretically and experimentally. In the experiments, they moved the STM tip relative to the edge of the gold grating and observed the generated light using an inverted microscope (see image).“The STM tip acts as a point source of surface plasmons,” Yang explains. “When placed on a metal film, electrons that tunnel across the gap can excite plasmons, although inefficiently.” Yang likens the excitation of plasmons in gratings to dropping pebbles in a swimming pool with swimming lanes demarcated by floats. “What is interesting is that depending on how far we drop the pebble from the barrier for each lane, we can get waves that preferentially move away from the barrier and even across lanes. By adjusting the position just by a small amount — in our case by about 100 nanometers — we can turn on waves that propagate in the opposite direction, namely toward the barrier and beyond.” This control of direction stems from the surface plasmon polariton reflected from the grating edge interfering with the one at the STM probe. By modeling this process on a computer, the researchers found a good match with the experimental results. The result provides point sources of surface plasmon polaritons. This could prove useful for developing ways to replace wires between chips with optical connectors, which will greatly speed up chip-to-chip communication in integrated circuits based on plasmonics rather than electronics. The researchers intend to investigate the optical characteristics of the plasmon source when the electrically excited plasmons are coupled to plasmonic waveguides, opening the way to plasmonic counterparts of electronic components. “Potentially, we hope to achieve logic gates, which underpin all processing circuits, based on electrically driven plasmons,” says Dong.
First-principles simulations reveal distribution of absorbed hydrogen atoms (cyan) on a small platinum nanoparticle catalyst during hydrogen evolution reaction. (© ACS) Platinum nanoparticles are used in the catalysis of many reactions, including the important hydrogen evolution reaction used in fuel cells and for separating water into oxygen and hydrogen. Improved effectiveness of platinum nanoparticles to catalyze this reaction had been experimentally shown with decreasing nanoparticle size until it fell below about 3 nanometers. There was no clear explanation for why catalytic activity was reduced at this scale. Teck Leong Tan and colleagues at the A*STAR Institute of High Performance Computing, and collaborators at the Ames Laboratory in the USA, performed first-principles calculations of platinum nanoparticles for the hydrogen evolution reaction. Based on these calculations, they produced a map of the intermediate compounds — in this case adsorbed hydrogen atoms — that form on the nanoparticles. They also estimated the contribution made by each catalytic active species to the overall activity. An effective catalyst must not bind to reaction intermediates too weakly because reactants will fail to bind to its surface. Too strong an adherence will cause difficulty for reaction products to detach from the catalyst surface. The binding energy of an effective catalyst should be ‘just right’, lying somewhere between these two extremes. The researchers found that edge sites on small platinum nanoparticles bind too strongly to hydrogen atoms and become inactive catalytically, but face sites continue to bind with hydrogen with an appropriate energy level and remain catalytically active. The increased ratio of edge sites to face sites as nanoparticle size reduces explains the observed fall in catalytic activity for small nanoparticles. It also suggests that the nanoparticle shape could be tailored to optimize the nanoparticle’s catalytic activity. The simulation results augur well for the potential of this technique. “Experimentalists have long been trying to visualize the structure of nanosized catalysts and the adsorbate distribution in real-time during reactions,” explains Tan. “However, this is often difficult to achieve. Our first-principles computational method provides an accurate model of the catalyst structure with adsorbate coverage and thus allows researchers to visualize what is going on in catalysts during a reaction.” The computational method can be applied to nanoscale catalysts besides platinum, and the team is keen to explore its potential to predict the performance of nanoparticles of other elements.
A model system based on actin filaments is yielding insights into "flocking" or "swarming" behavior on the biomolecular level. (Image: Bausch & Suzuki / TUM) Experiments disprove popular theory In their experiments the researchers first immobilize motor proteins by fixing them to a glass slide. When actin filaments are added, together with a source of biochemical energy, they interact with the motors and exhibit active gliding motions. Moreover, individual filaments were found to locally adopt strongly curved configurations. The team analyzed their statistics to understand what happens when filaments collide and under what conditions interacting filaments align themselves in collective, streaming motions. In living organisms, actin microfilaments are involved in the active migration of nucleated cells and in intracellular transport processes. According to the most popular theory, the fact that thin actin filaments bend as they are propelled by motor proteins is attributable to random thermal fluctuations, i.e., Brownian motion. But this assumption is false, says Christoph Weber, first author of the PNAS paper. Brownian motion has only a very weak impact on the form of the filaments. The researchers found that the molecular motors are not only responsible for propelling the fibers, but also for causing them to form strong bends. "The filaments exhibit a range of local curvatures, the statistical distribution of which is incompatible with thermally driven motion," explains Ryo Suzuki, first author of the paper in Nature Physics. Two by two won't do In addition, the assumption that the interactions in the system are always binary in nature is not sufficient to explain the fact that, at high densities, filaments can align with each other and begin to display directed, collective motions. In fact, simultaneous encounters involving multiple agents appear to be required to account for the emergence of such collective motion. In this case, the filaments, each of which is composed of multiple subunits, apparently remain in stable alignment with each other and interact not only pairwise, but also with many other partners. The scientists observed that, depending on the density and the mean length of the filaments, a phase transition occurs in which a state of non-directed movements is abruptly transformed into one characterized by collective motions ("swarm formation"). This transition resembles the condensation of a gas into the liquid state, except that in this case, it is not the pattern of microscopic molecular motions that changes but the orientation of the molecules in the system. From a theoretical point of view, this strengthens the argument that the currently favored model for the motions of actively driven particles, which is based on the kinetic theory of gases, cannot adequately account for the behavior of such systems. Instead, it appears as if the filaments themselves act in a coordinated fashion, like molecules in a fluid state. "To understand how collective motion arises in these systems, we need to develop new theoretical concepts which go beyond the assumptions of the kinetic theory of gases," says LMU Prof. Erwin Frey. Exactly what happens at the microscopic level when filaments come into alignment, i.e., how their subunits interact with neighbors or exchange places, is not yet clear. "A better understanding of the physics of active systems," says TUM Prof. Andreas Bausch, "opens the way to determining the basic mechanisms leading to structures and patterns enabling life, and could permit scientists to construct entirely novel nanosystems based on collective behaviors." Publications Ryo Suzuki, Christoph A. Weber, Erwin Frey and Andreas R. Bausch: Polar pattern formation in driven filament systems requires non-binary particle collisions. 2015. Christoph A. Weber, Ryo Suzuki, Volker Schaller, Igor S. Aranson, Andreas R. Bausch, and Erwin Frey: Random bursts determine dynamics of active filaments. 2015.
Artificial photosynthesis used to produce renewable molecular hydrogen for synthesizing carbon dioxide into methane. Yang, who also holds appointments with UC Berkeley and the Kavli Energy NanoScience Institute (Kavli-ENSI) at Berkeley, is one of three corresponding authors of a paper describing this research in the . The paper is titled “A hybrid bioinorganic approach to solar-to-chemical conversion”. The other corresponding authors are Michelle Chang and Christopher Chang. Both also hold joint appointments with Berkeley Lab and UC Berkeley. In addition, Chris Chang is a Howard Hughes Medical Institute (HHMI) investigator. (See below for a full list of the paper’s authors.) Photosynthesis is the process by which nature harvests the energy in sunlight and uses it to synthesize carbohydrates from carbon dioxide and water. Carbohyrates are biomolecules that store the chemical energy used by living cells. In the original hybrid artificial photosynthesis system developed by the Berkeley Lab team, an array of silicon and titanium oxide nanowires collected solar energy and delivered electrons to microbes which used them to reduce carbon dioxide into a variety of value-added chemical products. In the new system, solar energy is used to split the water molecule into molecular oxygen and hydrogen. The hydrogen is then transported to microbes that use it to reduce carbon dioxide into one specific chemical product, methane. “In our latest work, we’ve demonstrated two key advances,” says Chris Chang. “First, our use of renewable hydrogen for carbon dioxide fixation opens up the possibility of using hydrogen that comes from any sustainable energy source, including wind, hydrothermal and nuclear. Second, having demonstrated one promising organism for using renewable hydrogen, we can now, through synthetic biology, expand to other organisms and other value-added chemical products.” The concept in the two studies is essentially the same - a membrane of semiconductor nanowires that can harness solar energy is populated with bacterium that can feed off this energy and use it to produce a targeted carbon-based chemical. In the new study, the membrane consisted of indium phosphide photocathodes and titanium dioxide photoanodes. Whereas in the first study, the team worked with Sporomusa ovata, an anaerobic bacterium that readily accepts electrons from the surrounding environment to reduce carbon dioxide, in the new study the team populated the membrane with Methanosarcina barkeri, an anaerobic archaeon that reduces carbon dioxide using hydrogen rather than electrons. “Using hydrogen as the energy carrier rather than electrons makes for a much more efficient process as molecular hydrogen, through its chemical bonds, has a much higher density for storing and transporting energy,” says Michelle Chang. In the newest membrane reported by the Berkeley team, solar energy is absorbed and used to generate hydrogen from water via the hydrogen evolution reaction (HER). The HER is catalyzed by earth-abundant nickel sulfide nanoparticles that operate effectively under biologically compatible conditions. Hydrogen produced in the HER is directly utilized by the Methanosarcina barkeri archaeons in the membrane to produce methane. “We selected methane as an initial target owing to the ease of product separation, the potential for integration into existing infrastructures for the delivery and use of natural gas, and the fact that direct conversion of carbon dioxide to methane with synthetic catalysts has proven to be a formidable challenge,” says Chris Chang. “Since we still get the majority of our methane from natural gas, a fossil fuel, often from fracking, the ability to generate methane from a renewable hydrogen source is another important advance.” Adds Yang, “While we were inspired by the process of natural photosynthesis and continue to learn from it, by adding nanotechnology to help improve the efficiency of natural systems we are showing that sometimes we can do even better than nature.”
Schematic illustration of single molecule-junctions consisting stacks of aromatic molecules in a self-assembled cage and the corresponding electronic components of the junctions. The assembled cage is sandwiched by two Au electrodes. Empty cage (a), homo-stacks and hetero-stacked pair (c) develop functions of resistor, wire and diode, respectively. (click on image to enlarge) The empty cage presents a low electronic conductance (10
Ionization times (left axis) reconstructed using the ARM theory from offset angles (right axis) obtained numerically using TDSE calculations. Red circles are the numerically calculated offset angles, divided by the laser frequency, θ/ω. Blue diamonds show the offset angles with the correction due to the substraction of the pulse envelope effect, ti
Liquid flatjet system, showing the two nozzles from which two impinging single jets form a 1 mm wide and 5 mm long liquid water sheet with a thickness of 1 - 2 µm as determined by measuring the transmission at the oxygen K absorption edge (left), with which XAS measurements in transmission can be made on aqueous solutions, as exemplified with the nitrogen K absorption edge spectrum of ammoniumchloride (right). (Image: MBI) (click on image to enlarge) A collaboration between scientists from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI), the Helmholtz-Zentrum Berlin (HZB) and the Max Planck Institute for Dynamics and Self-Organization (MPIDS) have now demonstrated the successful implementation of a liquid flatjet with a thickness in the Ã…-µm range, allowing for XAS transmission measurements in the soft-x-ray regime ("A liquid flatjet system for solution phase soft-x-ray spectroscopy"). Here a phenomenon well known in the field of fluid dynamics has been applied: by obliquely colliding two identical laminar jets, the liquid expands radially, generating a sheet in the form of a leaf, bounded by a thicker rim, orthogonal to the plane of the impinging jets. The novel aspect here is that a liquid water flatjet has been demonstrated with thicknesses in the few micrometer range, stable for tens to hundreds of minutes, fully operational under vacuum conditions (‹10-3 mbar). For the first time, soft x-ray absorption spectra of a liquid sample could be measured in transmission without any membrane. The x-ray measurements were performed at the soft x-ray synchrotron facility BESSYII of the Helmholtz-Zentrum Berlin. This technological breakthrough opens up new frontiers in steady-state and time-resolved soft-x-ray spectroscopy of solution phase systems.
The x-ray diffraction patterns with inclination angle of 45° observed for 0.07YO
Martina Abrigo Using a technique called electrospinning – in which polymer filaments 100 times thinner than a human hair are squeezed out of an electrified nozzle – Ms Abrigo and her colleagues have made nanofibre meshes that can draw bacteria from a wound. In the first phase of research polymer nanofibres were placed over the top of films of Staphylococcus aureus, a bacterium involved in chronic wound infection. The researchers found the bacteria quickly attached to the fibres. When the fibres were smaller than the individual bacteria, fewer cells attached and those that did attach died as they attempted to wrap around the fibre. In the second phase, the tiny nanofibres were coated with different compounds and tested on the bacteria Escherichia coli, also commonly found in chronic wounds. The researchers found these bacteria rapidly transferred onto fibres coated with allylamine, independent of the fibre size, but did not attach to fibres coated with acrylic acid. In the third phase of research, the nanofibre meshes have been tested on tissue-engineered skin models in a partnership with researchers at the University of Sheffield in the UK. The results of this research are yet to be published, but indicate that similar effects could be seen in living tissue. “For most people, wounds heal quickly. But for some people, the repair process gets stuck and so wounds take much longer to heal. This makes them vulnerable to infection,” Mas Abrigo said. “We hope this work will lead to smart wound dressings that could prevent infections. Doctors could put a nanomesh dressing on a wound and simply peel it off to get rid of the germs.” A paper on bacterial response to meshes with different fibre diameters was published in ("Electrospun Polystyrene Fiber Diameter Influencing Bacterial Attachment, Proliferation, and Growth"). A paper investigating the effect of fibre surface chemistry on bacterial behaviour was published in ("Bacterial response to different surface chemistries fabricated by plasma polymerization on electrospun nanofibers").
Supramolecular nanofiber consisting of more than 10,000 perfectly ordered building blocks, which enables an energy transport over a distance of more than 4 micrometers at room temperature. (Image: A. T. Haedler) The research groups of Richard Hildner in Experimental Physics and Hans-Werner Schmidt in Macromolecular Chemistry at the University of Bayreuth prepared supramolecular nanofibers, which can consist of more than 10,000 identical building blocks. The core of the building block is a so-called carbonyl-bridged triarylamine. This triarylamine derivative was synthesized by the research group of Milan Kivala in Organic Chemistry at the University of Erlangen-Nuremberg and chemically modified at the University of Bayreuth. Three naphthalimidbithiophene chromophores are linked to this central unit. Under specific conditions, the building blocks spontaneously self-assemble and form nanofibers with lengths of more than 4 micrometers and diameters of only 0.005 micrometer. For comparison: a human hair has a thickness of 50 to 100 micrometers. With a combination of different microscopy techniques the scientists at the University of Bayreuth were able to visualize the transport of excitation energy along these nanofibers. In order to achieve this long-range energy transport, the triarylamine cores of the building blocks, that are perfectly arranged face to face, act in concert. Thus, the energy can be transferred in a wave-like manner from one building block to the next: This phenomenon is called quantum coherence. “These highly promising nanostructures demonstrate that carefully tailoring materials for the efficient transport of light energy is an emerging research area” says Dr. Richard Hildner, an expert in the field of light harvesting at the University of Bayreuth. The research area light harvesting aims at a precise description of the transport processes in natural photosynthetic machineries to use this knowledge for building novel nanostructures for power generation from sunlight. In this field interdisciplinary groups of researchers work together in the Bavarian initiative Solar Technologies Go Hybrid and in the Research Training Group Photophysics of synthetic and biological multichromophoric systems (GRK 1640) funded by the German Research Foundation (DFG).
A scanning electron microscope image shows cobalt-infused metal oxide-laser induced graphene produced at Rice University. The material may be a suitable substitute for platinum or other expensive metals as catalysts for fuel cells. The scale bar equals 10 microns. (Image: Tour Group/Rice University) With the discovery, the material that the researchers call "metal oxide-laser induced graphene" (MO-LIG) becomes a new candidate to replace expensive metals like platinum in catalytic fuel-cell applications in which oxygen and hydrogen are converted to water and electricity. "The wonderful thing about this process is that we can use commercial polymers, with simple inexpensive metal salts added," Tour said. "We then subject them to the commercial laser scriber, which generates metal nanoparticles embedded in graphene. So much of the chemistry is done by the laser, which generates graphene in the open air at room temperature. "These composites, which have less than 1 percent metal, respond as 'super catalysts' for fuel-cell applications. Other methods to do this take far more steps and require expensive metals and expensive carbon precursors." Initially, the researchers made laser-induced graphene with commercially available polyimide sheets. Later, they infused liquid polyimide with boron to produce laser-induced graphene with a greatly increased capacity to store an electrical charge, which made it an effective supercapacitor. 
Rice University chemists embedded metallic nanoparticles into laser-induced graphene. The particles turn the material into a useful catalyst for fuel cell and other applications. (Image: Tour Group/Rice University) For the latest iteration, they mixed the liquid and one of three concentrations containing cobalt, iron or molybdenum metal salts. After condensing each mixture into a film, they treated it with an infrared laser and then heated it in argon gas for half an hour at 750 degrees Celsius. That process produced robust MO-LIGs with metallic, 10-nanometer particles spread evenly through the graphene. Tests showed their ability to catalyze oxygen reduction, an essential chemical reaction in fuel cells. Further doping of the material with sulfur allowed for hydrogen evolution, another catalytic process that converts water into hydrogen, Tour said. "Remarkably, simple treatment of the graphene-molybdenum oxides with sulfur, which converted the metal oxides to metal sulfides, afforded a hydrogen evolution reaction catalyst, underscoring the broad utility of this approach," he said.
The zipped (left) and unzipped (right) forms of the protein GCN4-p1passing through a pore are shown. The differences in shape between the dimer and monomer versions of the protein translate to changes in charge, which can be read by electronics surrounding the nanopore. (Inage: Jeffery Saven and Wenhao Liu) The study was led by Marija Drndic, a professor in the School of Arts & Sciences' Department of Physics & Astronomy; David Niedzwiecki, a postdoctoral researcher in her lab; and Jeffery G. Saven, a professor in Penn Arts & Sciences' Department of Chemistry. It was published in the journal ("Observing Changes in the Structure and Oligomerization State of a Helical Protein Dimer Using Solid-State Nanopores"). The Penn team's technique stems from Drndic's work on nanopore gene sequencing, which aims to distinguish the bases in a strand of DNA by the different percent of the aperture they each block as they pass through a nanoscopic pore. Different silhouettes allow different amounts of an ionic liquid to pass through. The change in ion flow is measured by electronics surrounding the pore; the peaks and valleys of that signal can be correlated to each base. While researchers work to increase the accuracy of these readings to useful levels, Drndic and her colleagues have experimented with applying the technique to other biological molecules and nanoscale structures. Collaborating with Saven's group, they set out to test their pores on even trickier biological molecules. "There are many proteins that are much smaller and harder to manipulate than a strand of DNA that we'd like to study," Saven said. "We're interested in learning about the structure of a given protein, such as whether it exists as a monomer, or combined with another copy into a dimer, or an aggregate of multiple copies known as an oligomer." Detection is also often a limitation. "There are no ways to amplify peptides and proteins like there are for DNA," Drndic said. "If you want to study proteins from a particular source, you're stuck with very small samples. With this method, however, you can just collect the amount of data you need and the number of proteins you want to pass through the pore and then study them one at a time as they naturally exist in the body." Using the Drndic group's silicon nitride nanopores, which can be drilled to custom diameters, the research team set out to test their technique on GCN4-p1, a protein selected because it contains a common structural motif found in transcription factors and intracellular receptors. "The dimer version is 'zipped' together," Niedzwiecki said, "It is a 'coiled coil' of interleaved helices that is roughly cylindrical. The monomer version is unzipped and is likely not helical; it's probably more like a string." The researchers put different ratios of zipped and unzipped versions of the protein in an ionic fluid and passed them through the pores. While unable to tell the difference between individual proteins, the researchers could perform this analysis on populations of the molecule. "The dimer and monomer form of the protein block a different number of ions, so we see a different drop in current when they go through the pore," Niedzwiecki said. "But we get a range of values for both, as not every molecular translocation event is the same." Determining whether a specific sample of these types of proteins are aggregating or not could be used to better understand the progression of disease. "Many researchers," Saven said, "have observed these long tangles of aggregated peptides and proteins in diseases like Alzheimer's and Parkinson's, but there is an increasing body of evidence that is suggesting these tangles are occurring after the fact, that what are really causing the problem are smaller protein assemblies. Figuring out what those assemblies are and how large they are is currently really hard to do, so this may be a way of solving that problem."
One of the metallic samples studied, niobium diselenide, is seen here–the square in the center–as prepared for an X-ray diffraction experiment. (Image: University of Chicago/Argonne National Laboratory) "We spent over 10 years developing the instrumentation to perform these studies," says Yejun Feng of Argonne National Laboratory, a coauthor of the paper. "We now have a very unique capability that's due to the long-term relationship between Dr. Rosenbaum and the facilities at the Argonne National Laboratory." Within atoms, electrons are organized into orbital shells and subshells. Although they are often depicted as physical entities, orbitals actually represent probability distributions—regions of space where electrons have a certain likelihood of being found in a particular element at a particular energy. The characteristic electron configuration of a given element explains that element's peculiar properties. The work in correlated electrons looks at a subset of electrons. Metals, as an example, have an unfilled outermost orbital and electrons are free to move from atom to atom. Thus, metals are good electrical conductors. When metal atoms are tightly packed into lattices (or crystals) these electrons mingle together into a "sea" of electrons. The metallic element mercury is liquid at room temperature, in part due to its electron configuration, and shows very little resistance to electric current due to its electron configuration. At 4 degrees above absolute zero (just barely above -460 degrees Fahrenheit), mercury's electron arrangement and other properties create communal electrons that show no resistance to electric current, a state known as superconductivity. Mercury's superconductivity and similar phenomena are due to the existence of many pairs of correlated electrons. In superconducting states, correlated electrons pair to form an elastic, collective state through an excitation in the crystal lattice known as a phonon (specifically, a periodic, collective excitation of the atoms). The electrons are then able to move cooperatively in the elastic state through a material without energy loss. Electrons in crystals can interact in many ways with the periodic structure of the underlying atoms. Sometimes the electrons modulate themselves periodically in space. The question then arises as to whether this "charge order" derives from the interactions of the electrons with the atoms, a theory first proposed more than 60 years ago, or solely from interactions among the sea of electrons themselves. This question was the focus of the Nature Physics study. Electrons also behave as microscopic magnets and can demonstrate "spin order," which raises similar questions about the origin of the local magnetism. To see where the charge order arises, the researchers turned to the Advanced Photon Source at Argonne. The Photon Source is a synchrotron (a relative of the cyclotron, commonly known as an "atom-smasher"). These machines generate intense X-ray beams that can be used for X-ray diffraction studies. In X-ray diffraction, the patterns of scattered X-rays are used to provide information about repeating structures with wavelengths at the atomic scale. 
This cutaway schematic shows the diamond anvil cell, a pressure vessel in which the experiments were conducted. The target material is situated between two diamonds, represented here in blue. For this study, a diamond anvil generated pressures to 100,000 times sea level. (Image: University of Chicago/Argonne National Laboratory) In the experiment, the researchers used the X-ray beams to investigate charge-order effects in two metals, chromium and niobium diselenide, at pressures ranging from 0 (a vacuum) to 100 kilobar (100,000 times normal atmospheric pressure) and at temperatures ranging from 3 to 300 K (or -454 to 80 degrees Fahrenheit). Niobium diselenide was selected because it has a high degree of charge order, while chromium, in contrast, has a high degree of spin order. The researchers found that there is a simple correlation between pressure and how the communal electrons organize themselves within the crystal. Materials with completely different types of crystal structures all behave similarly. "These sorts of charge- and spin-order phenomena have been known for a long time, but their underlying mechanisms have not been understood until now," says Rosenbaum. Paper coauthors Jasper van Wezel, formerly of Argonne National Laboratory and presently of the Institute for Theoretical Physics at the University of Amsterdam, and Peter Littlewood, a professor at the University of Chicago and the director of Argonne National Laboratory, helped to provide a new theoretical perspective to explain the experimental results. Rosenbaum and colleagues point out that there are no immediate practical applications of the results. However, Rosenbaum notes, "This work should have applicability to new materials as well as to the kind of interactions that are useful to create magnetic states that are often the antecedents of superconductors," says Rosenbaum. "The attraction of this sort of research is to ask fundamental questions that are ubiquitous in nature," says Rosenbaum. "I think it is very much a Caltech tradition to try to develop new tools that can interrogate materials in ways that illuminate the fundamental aspects of the problem." He adds, "There is real power in being able to have general microscopic insights to develop the most powerful breakthroughs."