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Recent innovations in LEDs have improved the energy efficiency of streetlights, but, until now, their glow still wastefully radiated beyond the intended area. A team of researchers from Taiwan and Mexico has developed a new lighting system design that harnesses high-efficiency LEDs and ensures they shine only where they’re needed, sparing surrounding homes and the evening sky from unwanted illumination. The team reported their findings in the open-access journal Optics Express. The proposed lamp is based on a novel three-part lighting fixture. The first part contains a cluster of LEDs, each of which is fitted with a special lens, called a Total Internal Reflection lens, that focuses the light so the rays are parallel to one another instead of intersecting. These lens-covered LEDs are mounted inside a reflecting cavity, which “recycles” the light and ensures that as much of it as possible is used to illuminate the target. Finally, as the light leaves the lamp it passes through a diffuser or filter that cuts down on unwanted glare. The combination of collimation and filtering also allows researchers to control the beam’s shape: the present design yields a rectangular light pattern ideally suited for street lighting, the researchers say. In addition to cutting light pollution and glare, the new model could also save energy. A general LED street light could reduce power consumption by 40 to 60 percent. The increased efficiency of the proposed design would likely save an additional 10 to 50 percent. Furthermore, the module would be simple to fabricate, since it comprises just four parts, including a type of LED bulb commonly used in the lighting industry.
The union of theory and practice makes broadband, low-loss optical devices practical, which is why two groups of Penn State engineers collaborated to design optical metamaterials that have custom applications that are easily manufactured. In the past, to control the optics of metamaterials, researchers used complicated structures including 3-dimensional rings and spirals that are difficult if not impossible to manufacture in large numbers and small sizes at optical wavelengths. From a practical perspective, simple and manufacturable nanostructures are necessary for creating high-performance devices. ”We must design nanostructures that can be fabricated,” says Theresa S. Mayer, Distinguished Professor of Electrical Engineering and co-director of Penn State’s nanofabrication laboratory. Designing materials that can allow a range of wavelengths to pass through while blocking other wavelengths is far more difficult than simply creating something that will transmit a single frequency. Minimizing the time domain distortion of the signal over a range of wavelengths is necessary, and the material also must be low loss. The design team looked at existing fishnet structured metamaterials and applied nature-inspired optimization techniques based on genetic algorithms. They optimized the dimensions of features such as the size of the fishnet and the thicknesses of the materials. One of the transformative innovations made by the researchers was the inclusion of nanonotches in the corners of the fishnet holes, creating a pattern that could be tuned to shape the dispersion over large bandwidths.
University of Nebraska-Lincoln materials engineers have developed a structural nanofiber that is both strong and tough, a discovery that could transform everything from airplanes and bridges to body armor and bicycles. Their findings are featured on the cover of the American Chemical Society’s journal, ACS Nano. “Our discovery adds a new material class to the very select current family of materials with demonstrated simultaneously high strength and toughness,” says the team’s leader, Yuris Dzenis, McBroom Professor of Mechanical and Materials Engineering and a member of UNL’s Nebraska Center for Materials and Nanoscience. Dzenis and colleagues developed an exceptionally thin polyacrilonitrile nanofiber, a type of synthetic polymer related to acrylic, using electrospinning. Dzenis suggests that toughness comes from the nanofibers’ low crystallinity. In other words, it has many areas that are structurally unorganized. These amorphous regions allow the molecular chains to slip around more, giving them the ability to absorb more energy.
Resistive memory cells (ReRAM) are regarded as a promising solution for future generations of computer memories. They will dramatically reduce the energy consumption of modern IT systems while significantly increasing their performance. Unlike the building blocks of conventional hard disk drives and memories, these novel memory cells are not purely passive components but must be regarded as tiny batteries. This has been demonstrated by researchers of Jülich Aachen Research Alliance. The new finding radically revises the current theory and opens up possibilities for further applications. The research group has already filed a patent application for their first idea on how to improve data readout with the aid of battery voltage. In complex experiments, the scientists from Forschungszentrum Jülich and RWTH Aachen University determined the battery voltage of typical representatives of ReRAM cells and compared them with theoretical values. This comparison revealed other properties (such as ionic resistance) that were previously neither known nor accessible.”The demonstrated internal battery voltage of ReRAM elements clearly violates the mathematical construct of the memristor theory. This theory must be expanded to a whole new theory–to properly describe the ReRAM elements,” says Eike Linn, a specialist for circuit concepts.
(Berkeley National Lab/YouTube) A worldwide race is on for scientists to develop ever more powerful X-ray microscopes. With ultra-high resolution X-ray optics at ultra-bright synchrotrons—such as the 120-meter-long Hard X-Ray Nanoprobe (HXN) being developed for the National Synchrotron Light Source II (NSLS-II) at Brookhaven Lab—researchers will see structure and chemistry deep inside natural and engineered materials as they address some of the biggest questions in materials science, physics, chemistry, environmental sciences, and biology. Unprecedented capabilities, however, bring critical technical challenges, but scientists at Brookhaven Lab are on the job. In this video of the 486th Brookhaven Lecture, Yong Chu illustrates unique challenges and innovative approaches for X-ray microscopy at the nanoscale. He also discusses measurement capabilities for the first science experiments at NSLS-II. Chu joined the Photon Sciences Directorate at Brookhaven Lab as group leader for the HXN beamline at NSLS-II in 2009.
The innovative research of a Montana State University student, Neerja Zambare, a senior from Pune, India, majoring in both chemical engineering and biological engineering, was selected as one of the country’s undergraduate researchers for her poster about a bio-cement that effectively plugs cracks near wells and drilling sites. Zambare exhibited her research poster, “Biofilm induced biomineralization in a radial flow reactor,” at the Council on Undergraduate Research’s Posters on the Hill Exhibition April 23-24 in Washington, D.C., one of the country’s most prestigious undergraduate research fairs. Zambare was accompanied by Robin Gerlach, MSU professor of chemical and biological engineering and Zambare’s research mentor. Gerlach said Zambare convinced him that she would be the right person to join his lab group in the Center for Biofilm Engineering. The group trained her and then asked her to join a project that the lab had been working on for some time—a bacterium that makes calcium carbonate and has potential applications in sealing ponds, plugging cracks emitting carbon dioxide near carbon sequestration wells as well as abandoned wells.
(arXiv) Two modifications have been made to a miniature ceramic anvil high pressure cell (mCAC) designed for magnetic measurements at pressures up to 12.6 GPa in a commercial superconducting quantum interference (SQUID) magnetometer. Replacing the Cu-Be piston in the former mCAC with a composite piston composed of the Cu-Be and ceramic cylinders reduces the background magnetization significantly smaller at low temperatures, enabling more precise magnetic measurements at low temperatures. A second modification to the mCAC is the utilization of a ceramic anvil with a hollow in the center of the culet surface. High pressures up to 5 GPa were generated with the “cupped ceramic anvil” with the culet size of 1.0 mm.
Susan Trolier-McKinstry to deliver Friday’s EMA plenary after AFOSR speaker cancels.
Last week I wrote about a memo sent by the deputy secretary of DOD to the entire agency encouraging proactive spending cuts, including cutbacks on travel, conferences, and training. It did not take long for DOD brass to embrace the recommendations, and we just got word that this week’s Electronic Materials and Applications meeting is affected. Unfortunately, the Friday morning plenary speaker, Kitt Reinhart, program manager at the Air Force Office of Scientific Research, did not get approval to attend the meeting and give the plenary talk.
The good news is that Susan Trolier-McKinstry from Pennsylvania State University has agreed to step up and deliver the Friday plenary talk. Her plenary talk is ”Designing Piezoelectric Films for Microelectromechanical Systems (MEMS)” and the abstract follows. She also is coauthor of three talks and chairing a session in the “Functional and Multifunctional Electroceramics” symposium. Busy lady!
ACerS and the Basic Science Division and the Electronics Division appreciate the generosity of both Reinhart and Trolier-McKinstry to share their time and expertise!
“Designing Piezoelectric Films for Microelectromechanical Systems (MEMS)”
Susan Trolier-McKinstry, Materials Science and Engineering Department and Materials Research Institute, Pennsylvania State University
Piezoelectric thin films are of increasing interest in low voltage microelectromechanical systems (MEMS) for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. Piezoelectric MEMS devices range over a wide range of length scales. On the extreme upper end are large area devices for applications such as adaptive optics. In this case, the piezoelectric film can be used to produce local deformation of a mirror surface, in order to correct figure errors associated with fabrication of the component or to correct for atmospheric distortion. For example, should a mission such as Gen-X be flown, it would require up to 10,000 square meters of actuatable optics in order to correct the figures of the nested hyperboloid reflecting segments. In this case, the “micro” in “microelectromechanical systems” is clearly a misnomer, although the fabrication techniques would involve conventional micromachining for patterning of the electrodes. Many Piezoelectric MEMS devices are fabricated at intermediate length scales (tens of microns to 1 centimeter). Here, examples will be given of piezoelectric energy harvesting devices. We have recently demonstrated improvements in the energy harvesting figure of merit for the piezoelectric layer by factors of 4–10. Finally, piezoelectric MEMS are also attracting attention at a substantially smaller size scale (tens of nanometers) as a potential replacement for CMOS electronics. Examples of the materials choice as well as specific devices at all three of these length scales will also be discussed.
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The two-dimensionality and structural flatness make graphene films ideal candidates for thin film devices and combination with other semiconductor materials. In this work, vertical light emitting diodes (VLEDs) with highly reflective membrane as current blocking layer and graphene transparent conductive layer have been fabricated and characterized. VLEDs show improved optical output and efficiency droop due to the current spreading effect of the hybrid electrode by preventing current crowding under the top electrode and increasing the internal and external quantum efficiency.
[Materials Views] By showing that tiny particles injected into a liquid crystal medium adhere to existing mathematical theorems, physicists at the University of Colorado Boulder have opened the door for the creation of a host of new materials with properties that do not exist in nature. The findings show that researchers can create a “recipe book” to build new materials of sorts using topology, a major mathematical field that describes the properties that do not change when an object is stretched, bent or otherwise “continuously deformed.” Published in the journal Nature, the study also is the first to experimentally show that some of the most important topological theorems hold up in the real material world, said CU-Boulder physics department’s Ivan Smalyukh, a study senior author. Once injected into a liquid crystal, the particles behaved as predicted by topology. “Our study shows that interaction between particles and molecular alignment in liquid crystals follows the predictions of topological theorems, making it possible to use these theorems in designing new composite materials with unique properties that cannot be encountered in nature or synthesized by chemists. These findings lay the groundwork for new applications in experimental studies of low-dimensional topology, with important potential ramifications for many branches of science and technology.” The research supports the goals laid out by the White House’s Materials Genome Initiative, Smalyukh said, which seeks to deploy “new advanced materials at least twice as fast as possible today, at a fraction of the cost.”
Like a fine wine or aged cheese, ultrastable glass takes a long time to make, needs special conditions and is considered quite valuable. Unfortunately, manufacturers who want to take advantage of the strengths of ultrastable glass don’t have the luxury of waiting hundreds of years for it to develop. While exploring ways to create this valuable material on a shorter timetable, researchers from the University of Wisconsin-Madison have gained some key insights into the bizarre structure of glasses as well as how it affects their properties. “In attempts to work with aged glasses, for example, people have examined amber,” says study coauthor Juan de Pablo, a University of Chicago professor of molecular theory. “Amber is a glass that has been aged millions of years, but you cannot engineer that material. You get what you get.” In many laboratories, scientists use a technique called vapor deposition to create specialized materials. Previous research by another of the new study’s coauthors, Mark Ediger, found that glasses grown in this manner—within a certain temperature range and on a specially prepared surface - are far more stable than ordinary glasses. Ediger determined that in order to achieve this degree of stability, molecules in the glass are arranged in a tightly packed manner like the multi-shaped objects in the popular videogame Tetris.
Researchers are aiming to develop a new class of materials with remarkable properties using one atom-thick substances such as graphene in a new collaborative project. The proposal, which will involve researchers from the Universities of Manchester, Cambridge, and Lancaster, has been awarded €13.4 million to form a “Synergy Group” by the European Research Council. It will aim to utilize two-dimensional substances, such as graphene, to engineer new types of materials that are just a few atoms thick, but nevertheless have the power to revolutionize the future development of devices such as solar cells, and flexible and transparent electronics. Starting with one atom-thick substances, which possess remarkable properties, the group will focus on ways in which they can be layered up to form “heterostructures.” These heterostructures will still be just a few atoms thick, but will combine the properties of the different two-dimensional materials which comprise them, effectively enabling developers to embed the functions of a device into its very fabric. For example, the research team envisage combining an atomic layer which functions as a sensor, with layers that function variously as an amplifier, transistor, or solar cell, for power generation. The resulting material, still just a few atomic layers in thickness, would be capable of running a whole circuit.
Batteries for Norfolk Southern Railway No. 999, just like automotive batteries, are rechargeable until they eventually die. A leading cause of damage and death in lead-acid batteries is sulfation, a degradation of the battery caused by frequent charging and discharging that creates an accumulation of lead sulfate. In a recent study, the researchers looked for ways to improve regular battery management practices. The methods had to be nondestructive, simple, and cheap—using as few sensors, electronics, and supporting hardware as possible while still remaining effective at identifying and decreasing sulfation. ”We wanted to reverse the sulfation to rejuvenate the battery and bring it back to life,” says Christopher Rahn, professor of mechanical engineering at Penn State. Rahn, along with mechanical engineering research assistants Ying Shi and Christopher Ferone, cycled a lead-acid battery for three months in the same way it would be used in a locomotive. They used a process called electroimpedance spectroscopy and full charge/discharge to identify the main aging mechanisms. Through this, the researchers identified sulfation in one of the six battery cells. They then designed a charging algorithm that could charge the battery and reduce sulfation, but was also able to stop charging before other forms of degradation occurred. The algorithm successfully revived the dead cell and increased the overall capacity.
Modern information processing allows for breathtaking switching rates of about a 100 billion cycles per second. New results from Ferenc Krausz’s Laboratory for Attosecond Physics of the Max Planck Institute of Quantum Optics, Garching, Germany, and Ludwig-Maximilians-Universität, Munich, could pave the way towards signal processing several orders of magnitude faster. In two groundbreaking complementary experiments a collaboration led by LAP-physicists has demonstrated that, under certain conditions, ultrashort light pulses of extremely high intensity can induce electric currents in otherwise insulating dielectric materials. Furthermore, they provided evidence that the fast oscillations of the electric field instantly alter the electrical and optical properties of the material, and that these changes can be reversed on a femtosecond time scale. This opens the door for signal processing rates reaching the petahertz domain, about 10,000 times faster than it is possible with the best state-of-the-art solid state microchips. The experiments were carried out in close cooperation with the theoretical group of Mark Stockman, Georgia State University.
Although nanoparticles with exquisite properties have been synthesized for a variety of applications, their incorporation into functional devices is challenging owing to the difficulty in positioning them at specified sites on surfaces. To develop a materials-general method for synthesizing nanoparticles on surfaces for broader applications, a mechanistic understanding of polymer-mediated nanoparticle formation is crucial. A Northwestern University group, led by Chad A. Mirkin, has designed a four-step synthetic process that enables independent study of the two most critical steps for synthesizing single nanoparticles on surfaces: phase separation of precursors and particle formation. Using this process, they have elucidate the importance of the polymer matrix in the diffusion of metal precursors to form a single nanoparticle and the three pathways that the precursors undergo to form nanoparticles. Based on this mechanistic understanding, the synthetic process is generalized to create metal (Au, Ag, Pt, and Pd), metal oxide (Fe2O3, Co2O3, NiO, and CuO), and alloy (AuAg) nanoparticles. This mechanistic understanding and resulting process represent a major advance in scanning probe lithography as a tool to generate patterns of tailored nanoparticles for integration with solid-state devices.
The International Commission on Glass and Pennsylvania State University have teamed up to offer an award to an outstanding early-career scientist working in glass-related research, which would allow the winner to attend and present a paper at the 23rd International Congress on Glass in 2013. The congress will be held July 1–5, 2013 in Prague.
The official title for honor is the Woldemar A. Weyl International Glass Science Award, and ICG and Penn State have now opened up the window for nominations the triennial honor.
The award is named in honor of the late professor and head of the former Department of Mineral Technology at Penn State. W.A. Weyl is considered to be a founder of the modern science of glass. He pioneered an interdisciplinary approach to studying materials science and created research alliances between private industry and academia. Before a three-decade career at Penn State, his early work allowed him to become the leader of glass research at the prestigious Kaiser Wilhelm Institute for Silica Research (later part of the Max Planck Institutes) at age 25. His monograph, Coloured Glasses, received international praise as the first definitive review of the modern theories on the structure and constitution of glasses.
The main criteria for the award are that that nominee is a scientist, 35 years old or less, “whose research and publications in the field of glass science shows ingenuity, initiative, and above all, innovative thinking.”
The award is comprehensive and covers travel expenses, room and board, registration fees and incidental expenses for the recipient’s attendance at the congress. The recipient also must present a paper at the congress and provide a manuscript. Organizers also will present the award winner with a certificate and a suitable memento during the Congress.
Interested parties can nominate themselves, or the nominations can come from colleagues, teachers, supervisors, or other appropriate persons. Supporting material should include letter(s) of recommendation along with the nominee’s CV and list of publications.
Nominations will be reviewed by an anonymous selection committee, appointed by the USA delegates to the International Glass Commission. Please note that the selection committee may request additional supporting information from nominees.
Nominations (with supporting material) must be received no later than Feb. 15, 2013, and the winner will be notified before March 15.
ACerS’ Glass and Optical Materials Division is providing assistance with the award, and the chair of GOMD will distribute the nomination material to the selection committee.
Nominations may be via mail or email. They should by mail to Prof. Kelly Simmons-Potter, University of Arizona, 1230 E. Speedway Blvd., Tucson, AZ 85721 USA or by email to email@example.com
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A new study shows that the availability of hydrogen plays a significant role in determining the chemical and structural makeup of graphene oxide. The study also found that after the material is produced, its structural and chemical properties continue to evolve for more than a month as a result of continuing chemical reactions with hydrogen. The Georgia Tech researchers began their studies with multilayer epitaxial graphene grown atop a silicon carbide wafer. Their samples included an average of ten layers of graphene. After oxidizing the thin films of graphene using the established Hummers method, the researchers examined their samples using XPS. Over about 35 days, they noticed the number of epoxide functional groups declining while the number of hydroxyl groups increased slightly. After about three months, the ratio of the two groups finally reached equilibrium. “We found that the material changed by itself at room temperature without any external stimulation,” said Suenne Kim, a postdoctoral fellow in Riedo’s laboratory. “The degree to which it was unstable at room temperature was surprising.”
Researchers from Vestfold University College in Norway have created a simple, efficient energy-harvesting device that uses the motion of a single droplet to generate electrical power. The new technology could be used as a power source for low-power portable devices, and would be especially suitable for harvesting energy from low frequency sources such as human body motion, write the authors in a paper accepted to the American Institute of Physics’ journal Applied Physics Letters. The harvester produces power when an electrically conductive droplet (mercury or an ionic liquid) slides along a thin microfabricated material called an electret film, which has a permanent electric charge built into it during deposition. Cyclic tilting of the device causes the droplet to accelerate across the film’s surface; the maximum output voltage (and power) occurs when the sliding droplet reaches its maximum velocity at one end of the film. A prototype of the fluidic energy harvester demonstrated a peak output power at 0.18 microwatts, using a single droplet 1.2 millimeters in diameter sliding along a 2-micrometer-thick electret film.
If vanadium oxide had its own TV infomercial, you’d already know: “It’s a metal. It’s an insulator. It’s a window coating and an optical switch.” And thanks to a new study by Rice University physicists - there’s more! The study shows how to reversibly alter VO2′s quirky electronic properties by treating it with the simplest of substances-hydrogen. When oxygen reacts with vanadium to form VO2, the atoms form crystals that look like long rectangular boxes. The vanadium atoms line up along the four edges of the box in regularly spaced rows. A single crystal of VO2 can have many of these boxes lined up side by side, and the crystals conduct electricity like wire as long as they are kept warm. “The weird thing about this material is that if you cool it, when you get to 67°C, it goes through a phase transition that is both electronic and structural. When the phase changes, and these pairings take place, the material changes from being a electrical conductor to an electrical insulator,” says Rice’s Douglas Natelson, lead co-author of the study in this week’s Nature Nanotechnology. In 2010, Natelson and postdoctoral research associate Jiang Wei began to systematically study the phase changes in VO2. Wei and graduate student Heng Ji began by using a process called vapor deposition to grow VO2 wires that were about 1,000 times smaller than a human hair. One set of experiments on wires that had been baked in the presence of hydrogen gas returned particularly odd readings. Wei, Ji and Natelson determined that the hydrogen was apparently modifying the VO2 nanowires, but only those in contact with metal electrodes.
US soldiers are increasingly weighed down by batteries to power weapons, detection devices and communications equipment. So the Army Research Laboratory has awarded a University of Utah-led consortium almost $15 million to use computer simulations to help design materials for lighter-weight, energy efficient devices and batteries. “We want to help the Army make advances in fundamental research that will lead to better materials to help our soldiers in the field,” says computing Professor Martin Berzins, principal investigator among five University of Utah faculty members who will work on the project. “One of Utah’s main contributions will be the batteries.” Of the five-year Army grant of $14,898,000, the University of Utah will retain $4.2 million for research plus additional administrative costs. The remainder will go to members of the consortium led by the University of Utah, including Boston University, Rensselaer Polytechnic Institute, Pennsylvania State University, Harvard University, Brown University, the University of California, Davis, and the Polytechnic University of Turin, Italy. The new research effort is based on the idea that by using powerful computers to simulate the behavior of materials on multiple scales - from the atomic and molecular nanoscale to the large or “bulk” scale—new, lighter, more energy efficient power supplies and materials can be designed and developed. Improving existing materials also is a goal. ”We want to model everything from the nanoscale to the soldier scale,” Berzins says. “It’s virtual design, in some sense.”
Producing hydrogen from non-fossil fuel sources is a problem that continues to elude many scientists but University of Delaware’s Erik Koepf thinks he may have discovered a solution. Koepf, a doctoral candidate in mechanical engineering, has designed a novel reactor that employs highly concentrated sunlight and zinc oxide powder to produce solar hydrogen, a truly clean, sustainable fuel with zero emissions. The reactor, which resembles a large cylinder, is comprised of layers of advanced, ultrahigh temperature insulation and ceramic materials. The conical geometry of the reactor’ design uses gravity to feed zinc oxide powder (the reactant) into the system through 15 hoppers perched on top of the device using special gears and a custom built control assembly Koepf developed at UD. Cooling blocks embedded in the structure keep the motors, a quartz window and the aperture ring, where the sunlight enters, cool. “The idea is to create a small, well-insulated cavity and subject it to highly concentrated sunlight from above,” explains Koepf. Once hot, the hoppers will feed zinc oxide powder (a benign substance resembling baking soda) onto the ceramic layer, causing a reaction that decomposes the powder into pure zinc vapor. In a subsequent step, the zinc will be reacted with water to produce solar hydrogen. “Essentially, we take zinc oxide powder and thermochemically store the energy of the sun in it, then bottle it,” explains Koepf.
Daylight acts on our body clock and stimulates the brain. Fraunhofer researchers have made use of this knowledge and worked with industry partners to develop a coating for panes of glass that lets through more light. Above all, it promotes the passage through the glass of those wavelengths of light that govern our hormonal balance. Most people prefer to live in homes that are airy and flooded with light. Nobody likes to spend much time in a dark and dingy room. That’s no surprise, since daylight gives us energy and has a major impact on our sense of wellbeing. It is a real mood lifter. Anti-reflective glass that is more transmissive overall to daylight is reserved for certain special applications, such as in glass covers for photovoltaic modules or in glazing for shop windows. The aim with this new kind of glass is to avoid nuisance reflections and to achieve maximum light transmission at the peak emission wavelength of sunlight. This is the wavelength at which the human retina is also most sensitive to light. “However, our biorhythms are not affected by the wavelengths that brighten a room the most, but rather by blue light,” explains graduate engineer Walther Glaubitt, a researcher at the Fraunhofer Institute for Silicate Research ISC in Würzburg. That is why he and his team have developed glass that is designed to be particularly transmissive to light in the blue part of the spectrum. The secret is a special, long-lasting and barely perceptible inorganic coating that is only 0.1 micrometers thick. “Nobody’s ever made glass like this before. It makes you feel as if the window is permanently open,” says Glaubitt. One reason the glass gives this impression is that it exhibits maximum transmission at wavelengths between 450 and 500 nanometers—which is exactly where the effects of blue light are at their strongest.