Lighting the way to miniature devices

A team of scientists including researchers at Agency for Science, Technology and Research (A*STAR), Singapore, has captured tiny flashes of light from an ultrathin layer of organic molecules sandwiched between two electrodes that could replace lasers and LEDs as signal sources for future miniature, ultrafast quantum computing and light-based communication systems.

To investigate electromagnetic waves called plasmons, which skim along the interface between two materials, Nikodem Tomczak from the A*STAR Institute of Materials Research and Engineering and colleagues collaborated with Christian A. Nijhuis from the National University of Singapore to construct a junction consisting of a layer of thiol molecules on a metal electrode and liquid gallium-indium alloy as a top electrode.

The team created plasmons by applying a voltage across the thiol layer. Although thiol is an insulator, the layer was thin enough for electrons to quantum tunnel between the electrodes, exciting plasmons on the thiol layer's surface in the process. The plasmons then decayed into photons, tiny pulses of light that Tomczak and his colleagues were able to detect.

"We were surprised that the light did not come from the whole junction, but instead just from very small spots that blink at different frequencies," said Tomczak.

The team found that the light generated by the plasmons was polarized, and that both the polarization and the wavelength of the light varied with the voltage applied across the junction and the molecules used to form the organic layer.

"The spots are diffraction-limited, polarized and their blinking follows power-law statistics," said Tomczak. "We need further experiments to confirm, but it is very similar to emission from other single photon sources, such as quantum dots or nanodiamonds."

Further evidence that the light is from plasmons decaying into a single photon came from Chu Hong Son and his team at the A*STAR Institute of High Performance Computing who modeled the spots as the product of the smallest possible source, a single dipole emitter, and achieved results consistent with the experimental observations.

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The above post is reprinted from materials provided by The Agency for Science, Technology and Research (A*STAR).Note: Content may be edited for style and length.

Journal Reference:

1. Ji Fang Tao, Hong Cai, Yuan Dong Gu, Jian Wu, Ai Qun Liu.Demonstration of a Photonic-Based Linear Temperature Sensor. IEEE Photonics Technology Letters, 2015; 27 (7): 767 DOI: 10.1109/LPT.2015.2392107 

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The Agency for Science, Technology and Research (A*STAR). "Lighting the way to miniature devices." ScienceDaily. ScienceDaily, 13 September 2016. <www.sciencedaily.com/releases/2016/09/160913120920.htm>.

Lightweight, wearable tech efficiently converts body heat to electricity

Lightweight, wearable tech efficiently converts body heat to electricity

 

Researchers have developed a new design for harvesting body heat and converting it into electricity for use in wearable electronics. The tech can be embedded in a T-shirt, as shown here on study co-lead Haywood Hunter, an undergraduate at NC State University.

Researchers at North Carolina State University have developed a new design for harvesting body heat and converting it into electricity for use in wearable electronics. The experimental prototypes are lightweight, conform to the shape of the body, and can generate far more electricity than previous lightweight heat harvesting technologies.

The researchers also identified the optimal site on the body for heat harvesting.

"Wearable thermoelectric generators (TEGs) generate electricity by making use of the temperature differential between your body and the ambient air," says Daryoosh Vashaee, an associate professor of electrical and computer engineering at NC State and corresponding author of a paper on the work.

"Previous approaches either made use of heat sinks -- which are heavy, stiff and bulky -- or were able to generate only one microwatt or less of power per centimeter squared (μW/cm2). Our technology generates up to 20 μW/cm2 and doesn't use a heat sink, making it lighter and much more comfortable."

The new design begins with a layer of thermally conductive material that rests on the skin and spreads out the heat. The conductive material is topped with a polymer layer that prevents the heat from dissipating through to the outside air. This forces the body heat to pass through a centrally-located TEG that is one cm2. Heat that is not converted into electricity passes through the TEG into an outer layer of thermally conductive material, which rapidly dissipates the heat. The entire system is thin -- only 2 millimeters -- and flexible.

"In this prototype, the TEG is only one centimeter squared, but we can easily make it larger, depending on a device's power needs," says Vashaee, who worked on the project as part of the National Science Foundation's Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) at NC State.

The researchers also found that the upper arm was the optimal location for heat harvesting. While the skin temperature is higher around the wrist, the irregular contour of the wrist limited the surface area of contact between the TEG band and the skin. Meanwhile, wearing the band on the chest limited air flow -- limiting heat dissipation -- since the chest is normally covered by a shirt.

In addition, the researchers incorporated the TEG into T-shirts. The researchers found that the T-shirt TEGs were still capable of generating 6 μW/cm2 -- or as much as 16 μW/cm2 if a person is running.
"T-shirt TEGs are certainly viable for powering wearable technologies, but they're just not as efficient as the upper arm bands," Vashaee says.

"The goal of ASSIST is to make wearable technologies that can be used for long-term health monitoring, such as devices that track heart health or monitor physical and environmental variables to predict and prevent asthma attacks," he says.

"To do that, we want to make devices that don't rely on batteries. And we think this design and prototype moves us much closer to making that a reality."

Story Source:
The above post is reprinted from materials provided by North Carolina State University. Note: Content may be edited for style and length.

Journal Reference:

1. Melissa Hyland, Haywood Hunter, Jie Liu, Elena Veety, Daryoosh Vashaee. Wearable thermoelectric generators for human body heat harvesting. Applied Energy, 2016; 182: 518 DOI: 10.1016/j.apenergy.2016.08.150

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North Carolina State University. "Lightweight, wearable tech efficiently converts body heat to electricity." ScienceDaily. ScienceDaily, 12 September 2016. <www.sciencedaily.com/releases/2016/09/160912132730.htm>.

 

New material to revolutionize water proofing

 

In addition to waterproofing, the new ability to control the properties of materials could be applied to a wide range of other coatings, said Mr Wong.

Credit: Image courtesy of Australian National University

Scientists at The Australian National University (ANU) have developed a new spray-on material with a remarkable ability to repel water.

The new protective coating could eventually be used to waterproof mobile phones, prevent ice from forming on aeroplanes or protect boat hulls from corroding.

"The surface is a layer of nanoparticles, which water slides off as if it's on a hot barbecue," said PhD student William Wong, from the Nanotechnology Research Laboratory at the ANU Research School of Engineering.
The team created a much more robust coating than previous materials by combining two plastics, one tough and one flexible.

"It's like two interwoven fishing nets, made of different materials," Mr Wong said.
The water-repellent or superhydrophobic coating is also transparent and extremely resistant to ultraviolet radiation.

Lead researcher and head of the Nanotechnology Research Laboratory, Associate Professor Antonio Tricoli, said the new material could change how we interact with liquids.
"It will keep skyscraper windows clean and prevent the mirror in the bathroom from fogging up," Associate Professor Tricoli said.

"The key innovation is that this transparent coating is able to stabilise very fragile nanomaterials resulting in ultra-durable nanotextures with numerous real-world applications."
The team developed two ways of creating the material, both of which are cheaper and easier than current manufacturing processes.

One method uses a flame to generate the nanoparticle constituents of the material. For lower temperature applications, the team dissolved the two components in a sprayable form.
In addition to waterproofing, the new ability to control the properties of materials could be applied to a wide range of other coatings, said Mr Wong.

"A lot of the functional coatings today are very weak, but we will be able to apply the same principles to make robust coatings that are, for example, anti-corrosive, self-cleaning or oil-repellent," he said.

Story Source:

The above post is reprinted from materials provided by Australian National University. Note: Content may be edited for style and length.

1. William S. Y. Wong, Zbigniew H. Stachurski, David R. Nisbet, Antonio Tricoli. Ultra-Durable and Transparent Self-Cleaning Surfaces by Large-Scale Self-Assembly of Hierarchical Interpenetrated Polymer Networks. ACS Applied Materials & Interfaces, 2016; 8 (21): 13615 DOI: 10.1021/acsami.6b03414

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Australian National University. "New material to revolutionize water proofing." ScienceDaily. ScienceDaily, 8 September 2016. <www.sciencedaily.com/releases/2016/09/160908120439.htm>.

 

 

New perovskite research discoveries may lead to solar cell, LED advances

 

 

 

This image is a rendition of a one-dimensional, needle-like nanocrystal, such as the one prepared by Vela in collaboration with scientists Emily Smith and Jacob Petrich. Vela's team has prepared a family of highly luminescent perovskite nanocrystals with shape correlated emission.

 

"Promising" and "remarkable" are two words U.S. Department of Energy's Ames Laboratory scientist Javier Vela uses to describe recent research results on organolead mixed-halide perovskites.

Perovskites are optically active, semiconducting compounds that are known to display intriguing electronic, light-emitting and chemical properties. Over the last few years, lead-halide perovskites have become one of the most promising semiconductors for solar cells due to their low cost, easier processability and high power conversion efficiencies. Photovoltaics made of these materials now reach power conversion efficiencies of more than 20 percent.

Vela's research has focused on mixed-halide perovskites. Halides are simple and abundant, negatively charged compounds, such as iodide, bromide and chloride. Mixed-halide perovskites are of interest over single-halide perovskites for a variety of reasons. Mixed-halide perovskites appear to benefit from enhanced thermal and moisture stability, which makes them degrade less quickly than single-halide perovskites, Vela said. He added they can be fine-tuned to absorb sunlight at specific wavelengths, which makes them useful for tandem solar cells and many other applications, including light emitting diodes (LEDs).Using these compounds, scientists can control the color and efficiency of such energy conversion devices.

Speculating that these enhancements had something to do with the internal structure of mixed-halide perovskites, Vela, who is also an associate professor of chemistry at Iowa State University (ISU), worked with scientists with expertise in solid-state nuclear magnetic resonance (NMR) at both Ames Laboratory and ISU. NMR is an analytical chemistry technique that provides scientists with physical, chemical, structural and electronic information about complex samples.

"Our basic question was what it is about these materials in terms of their chemistry, composition, and structure that can affect their behavior," said Vela.

Scientists found that depending on how the material is made there can be significant nonstoichiometric impurities or "dopants" permeating the material, which could significantly affect the material's chemistry, moisture stability and transport properties.

The answers came via the combination of the use of optical absorption spectroscopy, powder X-ray diffraction and for the first time, the advanced probing capabilities of lead solid-state NMR.
"We were only able to see these dopants, along with other semicrystalline impurities, through the use of lead solid-state NMR," said Vela.

Another major discovery scientists made was that solid state synthesis is far superior to solution-phase synthesis in making mixed-halide perovskites. According to Vela, the advanced spectroscopy and materials capabilities of Ames Laboratory and ISU were critical in understanding how various synthetic procedures affect the true composition, speciation, stability and optoelectronic properties of these materials.

"We found you can make clean mixed halide perovskites without semi-crystalline impurities if you make them in the absence of a solvent," Vela said.

According to Vela, the significance of their findings is multifold and they are only beginning to grasp the implications of those findings.

"One obvious implication is that our understanding of the amazing opto-electronic properties of these semiconductors was incomplete," said Vela. "We're dealing with a compound that is not inherently as simple as people thought."

The research is further discussed in a paper, "Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites," authored by Vela, Bryan A. Rosales, Long Men, Sarah D. Cady, Michael P. Hanrahan, and Aaron J. Rossini; and published online in Chemistry Materials. The work was supported by DOE's Office of Science.

Story Source:

The above post is reprinted from materials provided by DOE/Ames Laboratory. Note: Content may be edited for style and length.

Journal Reference:

1. Bryan A. Rosales, Long Men, Sarah D. Cady, Michael P. Hanrahan, Aaron J. Rossini, Javier Vela. Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites. Chemistry of Materials, 2016; DOI: 10.1021/acs.chemmater.6b01874

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DOE/Ames Laboratory. "New perovskite research discoveries may lead to solar cell, LED advances." ScienceDaily. ScienceDaily, 7 September 2016. <www.sciencedaily.com/releases/2016/09/160907113651.htm>.

 

'Materials that compute' advances as engineers demonstrate pattern recognition

 

 

This is a conceptual illustration of pattern recognition process performed by hybrid gel oscillator system.

 

The potential to develop "materials that compute" has taken another leap at the University of Pittsburgh's Swanson School of Engineering, where researchers for the first time have demonstrated that the material can be designed to recognize simple patterns. This responsive, hybrid material, powered by its own chemical reactions, could one day be integrated into clothing and used to monitor the human body, or developed as a skin for "squishy" robots.

"Pattern recognition for materials that compute," published in the AAAS journal Science Advances, continues the research of Anna C. Balazs, Distinguished Professor of Chemical and Petroleum Engineering, and Steven P. Levitan, the John A. Jurenko Professor of Electrical and Computer Engineering. Co-investigators are Yan Fang, lead author and graduate student researcher in the Department of Electrical and Computer Engineering; and Victor V. Yashin, Research Assistant Professor of Chemical and Petroleum Engineering.

The computations were modeled utilizing Belousov-Zhabotinsky (BZ) gels, a substance that oscillates in the absence of external stimuli, with an overlaying piezoelectric (PZ) cantilever. These so-called BZ-PZ units combine Dr. Balazs' research in BZ gels and Dr. Levitan's expertise in computational modeling and oscillator-based computing systems.

"BZ-PZ computations are not digital, like most people are familiar with, and so to recognize something like a blurred pattern within an image requires nonconventional computing," Dr. Balazs explained. "For the first time, we have been able to show how these materials would perform the computations for pattern recognition."

Dr. Levitan and Mr. Fang first stored a pattern of numbers as a set of polarities in the BZ-PZ units, and the input patterns are coded through the initial phase of the oscillations imposed on these units. The computational modeling revealed that the input pattern closest to the stored pattern exhibits the fastest convergence time to the stable synchronization behavior, and is the most effective at recognizing patterns. In this study, the materials were programmed to recognize black-and-white pixels in the shape of numbers that had been distorted.

Compared to a traditional computer, these computations are slow and take minutes. However, Dr. Yashin notes that the results are similar to nature, which moves at a "snail's pace."
"Individual events are slow because the period of the BZ oscillations is slow," Dr. Yashin said. "However, there are some tasks that need a longer analysis, and are more natural in function. That's why this type of system is perfect to monitor environments like the human body."

For example, Dr. Yashin said that patients recovering from a hand injury could wear a glove that monitors movement, and can inform doctors whether the hand is healing properly or if the patient has improved mobility. Another use would be to monitor individuals at risk for early onset Alzheimer's, by wearing footwear that would analyze gait and compare results against normal movements, or a garment that monitors cardiovascular activity for people at risk of heart disease or stroke.

Since the devices convert chemical reactions to electrical energy, there would be no need for external electrical power. This would also be ideal for a robot or other device that could utilize the material as a sensory skin.

"Our next goal is to expand from analyzing black-and-white pixels to grayscale and more complicated images and shapes, as well as to enhance the devices storage capability," Mr. Fang said. "This was an exciting step for us and reveals that the concept of "materials that compute" is viable."

The research is funded by a five-year National Science Foundation Integrated NSF Support Promoting Interdisciplinary Research and Education (INSPIRE) grant, which focuses on complex and pressing scientific problems that lie at the intersection of traditional disciplines.

"As computing performance technology is approaching the end of Moore's law growth, the demands and nature of computing are themselves evolving," noted Sankar Basu, NSF program director. "This work at the University of Pittsburgh, supported by the NSF, is an example of this groundbreaking shift away from traditional silicon CMOS-based digital computing to a non-von Neumann machine in a polymer substrate, with remarkable low power consumption. The project is a rare example of much needed interdisciplinary collaboration between material scientists and computer architects."

Story Source:
The above post is reprinted from materials provided by University of Pittsburgh. Note: Content may be edited for style and length.

Journal Reference:

1. Y. Fang, V. V. Yashin, S. P. Levitan, A. C. Balazs. Pattern recognition with "materials that compute". Science Advances, 2016; 2 (9): e1601114 DOI: 10.1126/sciadv.1601114

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University of Pittsburgh. "'Materials that compute' advances as engineers demonstrate pattern recognition." ScienceDaily. ScienceDaily, 2 September 2016. <www.sciencedaily.com/releases/2016/09/160902152046.htm>.

 

Bosch’s New Technology Injects Water into Your Engine – On Purpose 

Water is typically something you want to keep out of your engine, but a new engine design from Bosch actually injects water into the combustion chamber to enhance performance. Called WaterBoost, which sounds like something you would have on a powerboat, not a car, injects distilled water into the intakes. You may be thinking that since water is incompressible that this helps maximize power output, but in fact it is used to cool down the combustion chambers faster. Check out the video below that will demonstrate how the process works.

https://youtu.be/o5yLPUVViXI

This water injection allows the engine to operate at higher compression ratios, which in turn increases efficiency. This increase in efficiency means that fuel consumption can be decreased by 13 percent during acceleration. WaterBoost can be fitted to most modern engines, as it is just an add-on modification that can significantly improve your engine’s performance. A distilled water talk is held in the engine compartment, and by Bosch’s estimations, it only needs to be refilled every 2000 miles.

Believe it or not, water injection in engines isn’t actually that new of a technology. BMW uses it in their M4 GTS, and it has been used for many years in military aviation engines, according to CNET.

Image Source: Autoengplus

Bosch is the first company to widely manufacture a water injection system that drivers can use to modify their engine’s efficiency. Don’t worry, when applied correctly in the WaterBoost system, the water only benefits your engine, not harm it.

 

Electronic circuits printed at one micron resolution

Formation of microcircuit lines using a selective coating technique. (a) Schematic of selective coating technique. Only a hydrophilic region created through irradiation of parallel vacuum ultraviolet (PVUV) is coated with metal ink. (b) Electronic circuit with a line width of 5 ?m formed through selective coating. (c) Electrode lines with different widths. Lines as narrow as 1 ?m can be formed.

Credit: Image courtesy of National Institute for Materials Science (NIMS)

A research team consisting of MANA Independent Scientist Takeo Minari, International Center for Materials Nanoarchitectonics (MANA), NIMS, and Colloidal Ink developed a printing technique for forming electronic circuits and thin-film transistors (TFTs) with line width and line spacing both being 1 μm. Using this technique, the research team formed fully-printed organic TFTs with a channel length of 1 μm on flexible substrates, and confirmed that the TFTs operate at a practical level.

Printed electronics -- printing techniques to fabricate electronic devices using functional materials dissolved in ink -- is drawing much attention in recent years as a promising new method to create large-area semiconductor devices at low cost. Because these techniques enable the formation of electronic devices even on flexible substrates, they are expected to be applicable to new fields such as wearable devices. In comparison, conventional printing technologies allow the formation of circuits and devices with line widths only as narrow as several dozen micrometers. Accordingly, they are not applicable to the creation of minute devices suitable for practical use. Thus, there were high expectations for developing new printing techniques capable of consistently fabricating circuits with line widths of several micrometers or less.

In this study, the research team developed a printing technique capable of forming metal circuits with line width being 1 μm on flexible substrates. Using this technique, they fabricated minute organic TFTs. The principle of this printing technique is as follows: First, form hydrophilic and hydrophobic micro-patterns on the substrate by irradiating it with parallel vacuum ultraviolet (PVUV) at a wavelength of 200 nm or less. Then, coat only the hydrophilic patterns with metal nanoparticle inks. The use of a PVUV light source (Ushio Inc.) enabled us to focus emitted light on much smaller targets than conventional light sources. Moreover, the use of DryCure-Au -- metal nanoparticle ink that can form a conductive film at room temperature developed by Colloidal Ink -- enabled us to form devices and circuits at room temperature during the entire process. As a result, we are able to fully prevent distortion of flexible substrates by heat, and form and laminate circuits within the accuracy of several microns. In addition, we precisely tuned the gate overlap lengths of the printed organic TFTs fabricated by this technique, which was previously impossible due to accuracy issues. As a result, a practical mobility level of 0.3 cm2 V-1 s-1 was accomplished for the organic TFTs with the channel length of 1 μm.

In future studies, we will aim to apply the technique in various fields such as large-area flexible displays and sensors. Since the process we developed is applicable to bio-related materials, the technique may also be useful in medical and bioelectronics fields.

Story Source:

The above post is reprinted from materials provided by National Institute for Materials Science (NIMS). Note: Content may be edited for style and length.

Journal Reference:

1. Xuying Liu, Masayuki Kanehara, Chuan Liu, Kenji Sakamoto, Takeshi Yasuda, Jun Takeya, Takeo Minari. Spontaneous Patterning of High-Resolution Electronics via Parallel Vacuum Ultraviolet. Advanced Materials, 2016; 28 (31): 6568 DOI: 10.1002/adma.201506151

Cite This Page:National Institute for Materials Science (NIMS). "Electronic circuits printed at one micron resolution." ScienceDaily. ScienceDaily, 1 September 2016. <www.sciencedaily.com/releases/2016/09/160901093000.htm>.