Tag Archives: Wei Luo

Transparent wood more efficient than glass in windows?

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University of Maryland researchers are suggesting that transparent wood could be more energy efficient than glass. An Aug. 16, 2016 news item on ScienceDaily describes the research,

Engineers at the A. James Clark School of Engineering at the University of Maryland (UMD) demonstrate in a new study that windows made of transparent wood could provide more even and consistent natural lighting and better energy efficiency than glass.

An Aug. 16, 2016 University of Maryland news release (also on EurekAlert) which originated the news item, explains further,

In a paper just published in the peer-reviewed journal Advanced Energy Materials, the team, headed by Liangbing Hu of UMD’s Department of Materials Science and Engineering and the Energy Research Center lay out research showing that their transparent wood provides better thermal insulation and lets in nearly as much light as glass, while eliminating glare and providing uniform and consistent indoor lighting. The findings advance earlier published work on their development of transparent wood.

The transparent wood lets through just a little bit less light than glass, but a lot less heat, said Tian Li, the lead author of the new study. “It is very transparent, but still allows for a little bit of privacy because it is not completely see-through. We also learned that the channels in the wood transmit light with wavelengths around the range of the wavelengths of visible light, but that it blocks the wavelengths that carry mostly heat,” said Li.

The team’s findings were derived, in part, from tests on tiny model house with a transparent wood panel in the ceiling that the team built. The tests showed that the light was more evenly distributed around a space with a transparent wood roof than a glass roof.

The channels in the wood direct visible light straight through the material, but the cell structure that still remains bounces the light around just a little bit, a property called haze. This means the light does not shine directly into your eyes, making it more comfortable to look at. The team photographed the transparent wood’s cell structure in the University of Maryland’s Advanced Imaging and Microscopy (AIM) Lab.

Transparent wood still has all the cell structures that comprised the original piece of wood. The wood is cut against the grain, so that the channels that drew water and nutrients up from the roots lie along the shortest dimension of the window. The new transparent wood uses theses natural channels in wood to guide the sunlight through the wood.

As the sun passes over a house with glass windows, the angle at which light shines through the glass changes as the sun moves. With windows or panels made of transparent wood instead of glass, as the sun moves across the sky, the channels in the wood direct the sunlight in the same way every time.

“This means your cat would not have to get up out of its nice patch of sunlight every few minutes and move over,” Li said. “The sunlight would stay in the same place. Also, the room would be more equally lighted at all times.”

Working with transparent wood is similar to working with natural wood, the researchers said. However, their transparent wood is waterproof due to its polymer component. It also is much less breakable than glass because the cell structure inside resists shattering.

The research team has recently patented their process for making transparent wood. The process starts with bleaching from the wood all of the lignin, which is a component in the wood that makes it both brown and strong. The wood is then soaked in epoxy, which adds strength back in and also makes the wood clearer. The team has used tiny squares of linden wood about 2 cm x 2 cm, but the wood can be any size, the researchers said.

Here’s an image illustrating the research,

Caption: This is a wood composite as an energy efficient building material: Guided sunlight transmission and effective thermal insulation. Credit: University of Maryland and Advanced Energy Materials

Caption: This is a wood composite as an energy efficient building material: Guided sunlight transmission and effective thermal insulation. Credit: University of Maryland and Advanced Energy Materials

I have written about transparent wood twice before. There’s this April 1, 2016 posting about the work at the KTH Institute (Sweden) and a May 11, 2016 posting about some earlier work at the University of Maryland.

Here’s a link and a citation for the latest from the University of Maryland,

Wood Composite as an Energy Efficient Building Material: Guided Sunlight Transmittance and Effective Thermal Insulation by Tian Li, Mingwei Zhu, Zhi Yang, Jianwei Song, Jiaqi Dai, Yonggang Yao, Wei Luo, Glenn Pastel, Bao Yang, and Liangbing Hu. Advanced Energy Materials Version of Record online: 11 AUG 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

University of Maryland looks into transparent wood

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Is transparent wood becoming the material du jour? Following on the heels of my April 1, 2016 post about transparent wood and the KTH Royal Institute of Technology (Sweden), there’s a May 6, 2016 news item on ScienceDaily about the material and a team at the University of Maryland,

Researchers at the University of Maryland have made a block of linden wood transparent, which they say will be useful in fancy building materials and in light-based electronics systems.

Materials scientist Liangbing Hu and his team at the University of Maryland, College Park, have removed the molecule in wood, lignin, that makes it rigid and dark in color. They left behind the colorless cellulose cell structures, filled them with epoxy, and came up with a version of the wood that is mostly see-thru.

I wonder if this is the type of material that might be used in structures like the proposed Center of Nanoscience and Nanotechnology at Tel Aviv University building (my May 9, 2016 posting about a building design that features no doors or windows)?

Regardless, there’s more about this latest transparent wood in a May 5, 2016 Tufts University news release, which originated the news item,

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Remember “xylem” and “phloem” from grade-school science class? These structures pass water and nutrients up and down the tree. Hu and his colleagues see these as vertically aligned channels in the wood, a naturally-grown structure that can be used to pass light along, after the wood has been treated.

The resulting three-inch block of wood had both high transparency—the quality of being see-thru—and high haze—the quality of scattering light. This would be useful, said Hu, in making devices comfortable to look at. It would also help solar cells trap light; light could easily enter through the transparent function, but the high haze would keep the light bouncing around near where it would be absorbed by the solar panel.

They compared how the materials performed and how light worked its way through the wood when they sliced it two ways: one with the grain of the wood, so that the channels passed through the longest dimension of the block. And they also tried slicing it against the grain, so that the channels passed through the shortest dimension of the block.

The short channel wood proved slightly stronger and a little less brittle. But though the natural component making the wood strong had been removed, the addition of the epoxy made the wood four to six times tougher than the untreated version.

Then they investigated how the different directions of the wood affected the way the light passed through it. When laid down on top of a grid, both kinds of wood showed the lines clearly. When lifted just a touch above the grid, the long-channel wood still showed the grid, just a little bit more blurry. But the short channel wood, when lifted those same few millimeters, made the grid completely invisible.

Here’s a link to and a citation for the paper,

Highly Anisotropic, Highly Transparent Wood Composites by Mingwei Zhu, Jianwei Song, Tian Li, Amy Gong, Yanbin Wang, Jiaqi Dai, Yonggang Yao, Wei Luo, Doug Henderson, and Liangbing Hu. Advanced Materials DOI: 10.1002/adma.201600427 Article first published online: 4 MAY 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

‘Beleafing’ in magic; a new type of battery

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A Jan. 28, 2016 news item on ScienceDaily announces the ‘beleaf’,

Scientists have a new recipe for batteries: Bake a leaf, and add sodium. They used a carbonized oak leaf, pumped full of sodium, as a demonstration battery’s negative terminal, or anode, according to a paper published yesterday in the journal ACS Applied Materials Interfaces.

Scientists baked a leaf to demonstrate a battery. Credit: Image courtesy of Maryland NanoCenter

Scientists baked a leaf to demonstrate a battery.
Credit: Image courtesy of Maryland NanoCenter

A Jan. ??, 2016 Maryland NanoCenter (University of Maryland) news release, which originated the news item, provides more information about the nature (pun intended) of the research,

“Leaves are so abundant. All we had to do was pick one up off the ground here on campus,” said Hongbian Li, a visiting professor at the University of Maryland’s department of materials science and engineering and one of the main authors of the paper. Li is a member of the faculty at the National Center for Nanoscience and Technology in Beijing, China.

Other studies have shown that melon skin, banana peels and peat moss can be used in this way, but a leaf needs less preparation.

The scientists are trying to make a battery using sodium where most rechargeable batteries sold today use lithium. Sodium would hold more charge, but can’t handle as many charge-and-discharge cycles as lithium can.

One of the roadblocks has been finding an anode material that is compatible with sodium, which is slightly larger than lithium. Some scientists have explored graphene, dotted with various materials to attract and retain the sodium, but these are time consuming and expensive to produce.  In this case, they simply heated the leaf for an hour at 1,000 degrees C (don’t try this at home) to burn off all but the underlying carbon structure.

The lower side of the maple [?] leaf is studded with pores for the leaf to absorb water. In this new design, the pores absorb the sodium electrolyte. At the top, the layers of carbon that made the leaf tough become sheets of nanostructured carbon to absorb the sodium that carries the charge.

“The natural shape of a leaf already matches a battery’s needs: a low surface area, which decreases defects; a lot of small structures packed closely together, which maximizes space; and internal structures of the right size and shape to be used with sodium electrolyte,” said Fei Shen, a visiting student in the department of materials science and engineering and the other main author of the paper.

“We have tried other natural materials, such as wood fiber, to make a battery,” said Liangbing Hu, an assistant professor of materials science and engineering. “A leaf is designed by nature to store energy for later use, and using leaves in this way could make large-scale storage environmentally friendly.”

The next step, Hu said, is “to investigate different types of leaves to find the best thickness, structure and flexibility” for electrical energy storage.  The researchers have no plans to commercialize at this time.

Here’s a link to and a citation for the paper,

Carbonized-leaf Membrane with Anisotropic Surfaces for Sodium-ion Battery by Hongbian Li, Fei Shen, Wei Luo, Jiaqi Dai, Xiaogang Han, Yanan Chen, Yonggang Yao, Hongli Zhu, Kun Fu, Emily Hitz, and Liangbing Hu. ACS Appl. Mater. Interfaces, 2016, 8 (3), pp 2204–2210 DOI: 10.1021/acsami.5b10875 Publication Date (Web): January 4, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Is there a supercapacitor hiding in your tree?

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I gather the answer is: Yes, there is a supercapacitor in your tree as researchers at Oregon State University (OSU) have found a way to use tree cellulose as a building component for supercapacitors. From an April 7, 2014 news item on ScienceDaily,

Based on a fundamental chemical discovery by scientists at Oregon State University, it appears that trees may soon play a major role in making high-tech energy storage devices.

OSU chemists have found that cellulose — the most abundant organic polymer on Earth and a key component of trees — can be heated in a furnace in the presence of ammonia, and turned into the building blocks for supercapacitors.

An April 7, 2014 OSU news release (also on EurekAlert), which originated the news item portrays great excitement (Note: Links have been removed),

These supercapacitors are extraordinary, high-power energy devices with a wide range of industrial applications, in everything from electronics to automobiles and aviation. But widespread use of them has been held back primarily by cost and the difficulty of producing high-quality carbon electrodes.

The new approach just discovered at Oregon State can produce nitrogen-doped, nanoporous carbon membranes – the electrodes of a supercapacitor – at low cost, quickly, in an environmentally benign process. The only byproduct is methane, which could be used immediately as a fuel or for other purposes.

“The ease, speed and potential of this process is really exciting,” said Xiulei (David) Ji, an assistant professor of chemistry in the OSU College of Science, and lead author on a study announcing the discovery in Nano Letters, a journal of the American Chemical Society. The research was funded by OSU.

“For the first time we’ve proven that you can react cellulose with ammonia and create these N-doped nanoporous carbon membranes,” Ji said. “It’s surprising that such a basic reaction was not reported before. Not only are there industrial applications, but this opens a whole new scientific area, studying reducing gas agents for carbon activation.

“We’re going to take cheap wood and turn it into a valuable high-tech product,” he said.

The news release includes some technical information about the carbon membranes and information about the uses to which supercapacitors are put,

These carbon membranes at the nano-scale are extraordinarily thin – a single gram of them can have a surface area of nearly 2,000 square meters. That’s part of what makes them useful in supercapacitors. And the new process used to do this is a single-step reaction that’s fast and inexpensive. It starts with something about as simple as a cellulose filter paper – conceptually similar to the disposable paper filter in a coffee maker.

The exposure to high heat and ammonia converts the cellulose to a nanoporous carbon material needed for supercapacitors, and should enable them to be produced, in mass, more cheaply than before.

A supercapacitor is a type of energy storage device, but it can be recharged much faster than a battery and has a great deal more power. They are mostly used in any type of device where rapid power storage and short, but powerful energy release is needed.

Supercapacitors can be used in computers and consumer electronics, such as the flash in a digital camera. They have applications in heavy industry, and are able to power anything from a crane to a forklift. A supercapacitor can capture energy that might otherwise be wasted, such as in braking operations. And their energy storage abilities may help “smooth out” the power flow from alternative energy systems, such as wind energy.

They can power a defibrillator, open the emergency slides on an aircraft and greatly improve the efficiency of hybrid electric automobiles.

Besides supercapacitors, nanoporous carbon materials also have applications in adsorbing gas pollutants, environmental filters, water treatment and other uses.

“There are many applications of supercapacitors around the world, but right now the field is constrained by cost,” Ji said. “If we use this very fast, simple process to make these devices much less expensive, there could be huge benefits.”

Here’s a link to and a citation for the paper,

Pyrolysis of Cellulose under Ammonia Leads to Nitrogen-Doped Nanoporous Carbon Generated through Methane Formation by Wei Luo, Bao Wang, Christopher G. Heron, Marshall J. Allen, Jeff Morre, Claudia S. Maier, William F. Stickle, and Xiulei Ji. Nano Lett., Article ASAP DOI: 10.1021/nl500859p Publication Date (Web): March 28, 2014
Copyright © 2014 American Chemical Society

The article is behind a paywall.

One final observation, one of the researchers, William F. Stickle is affiliated with HewLett Packard and not Oregon State University as are the others.

Looking at nanoparticles with your smartphone

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Researcher Aydogan Ozcan and his team at the University of California at Los Angeles (UCLA) have developed a device which when attached to a smartphone allows the user to view viruses, bacteria, and/or nanoparticles. (Yikes, I understood nanoparticles were perceptible with haptic devices and that any work on developing optical capabilities was pretty rudimentary). From the UCLA Sept. 16, 2013 news release on EurekAlert,

Aydogan Ozcan, a professor of electrical engineering and bioengineering at the UCLA Henry Samueli School of Engineering and Applied Science, and his team have created a portable smartphone attachment that can be used to perform sophisticated field testing to detect viruses and bacteria without the need for bulky and expensive microscopes and lab equipment. The device weighs less than half a pound.

“This cellphone-based imaging platform could be used for specific and sensitive detection of sub-wavelength objects, including bacteria and viruses and therefore could enable the practice of nanotechnology and biomedical testing in field settings and even in remote and resource-limited environments,” Ozcan said. “These results also constitute the first time that single nanoparticles and viruses have been detected using a cellphone-based, field-portable imaging system.”

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In the ACS [American Chemical Society]  Nano paper, Ozcan details a fluorescent microscope device fabricated by a 3-D printer that contains a color filter, an external lens and a laser diode. The diode illuminates fluid or solid samples at a steep angle of roughly 75 degrees. This oblique illumination avoids detection of scattered light that would otherwise interfere with the intended fluorescent image.

Using this device, which attaches directly to the camera module on a smartphone, Ozcan’s team was able to detect single human cytomegalovirus (HCMV) particles. HCMV is a common virus that can cause birth defects such as deafness and brain damage and can hasten the death of adults who have received organ implants, who are infected with the HIV virus or whose immune systems otherwise have been weakened. A single HCMV particle measures about 150–300 nanometers; a human hair is roughly 100,000 nanometers thick.

In a separate experiment, Ozcan’s team also detected nanoparticles — specially marked fluorescent beads made of polystyrene — as small as 90-100 nanometers.

To verify these results, researchers in Ozcan’s lab used other imaging devices, including a scanning electron microscope and a photon-counting confocal microscope. These experiments confirmed the findings made using the new cellphone-based imaging device.

For some reason I’m completely gobsmacked by the notion that I could look at nanoparticles on a smartphone at sometime in the foreseeable future.

Here’s a citation and a link to the paper,

Fluorescent Imaging of Single Nanoparticles and Viruses on a Smart Phone by Qingshan Wei, Hangfei Qi, Wei Luo, Derek Tseng , So Jung Ki, Zhe Wan, Zoltán Göröcs, Laurent A. Bentolila, Ting-Ting Wu, Ren Sun, and Aydogan Ozcan. ACS Nano, Article ASAP DOI: 10.1021/nn4037706 Publication Date (Web): September 9, 2013
Copyright © 2013 American Chemical Society

This paper is behind a paywall. Ozcan’s work was last mentioned here in a Jan. 21, 2013 posting about self-assembling liquid lenses.

 

Table salt, acting as a heat scavenger, enables cheaper silicon nanostructures

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Recyclable, easily obtained, and inexpensive, there’s a magic ingredient which could make producing silicon nanostructures easier and cheaper according an Aug. 8, 2013 news item on Nanowerk,

Chemists at Oregon State University have identified a compound that could significantly reduce the cost and potentially enable the mass commercial production of silicon nanostructures – materials that have huge potential in everything from electronics to biomedicine and energy storage.

This extraordinary compound is called table salt.

The Aug. 8, 2013 Oregon State University news release, which originated the news item, describes the principle at work and possible applications for the technique,

By melting and absorbing heat at a critical moment during a “magnesiothermic reaction,” the salt prevents the collapse of the valuable nanostructures that researchers are trying to create. The molten salt can then be washed away by dissolving it in water, and it can be recycled and used again.

The concept, surprising in its simplicity, should open the door to wider use of these remarkable materials that have stimulated scientific research all over the world.

“This could be what it takes to open up an important new industry,” said David Xiulei Ji, an assistant professor of chemistry in the OSU College of Science. “There are methods now to create silicon nanostructures, but they are very costly and can only produce tiny amounts.

“The use of salt as a heat scavenger in this process should allow the production of high-quality silicon nanostructures in large quantities at low cost,” he said. “If we can get the cost low enough many new applications may emerge.”

Silicon, the second most abundant element in the Earth’s crust, has already created a revolution in electronics. But silicon nanostructures, which are complex structures much smaller than a speck of dust, have potential that goes far beyond the element itself.

Uses are envisioned in photonics, biological imaging, sensors, drug delivery, thermoelectric materials that can convert heat into electricity, and energy storage.

Batteries are one of the most obvious and possibly first applications that may emerge from this field, Ji said. It should be possible with silicon nanostructures to create batteries – for anything from a cell phone to an electric car – that last nearly twice as long before they need recharging.

Existing technologies to make silicon nanostructures are costly, and simpler technologies in the past would not work because they required such high temperatures. Ji developed a methodology that mixed sodium chloride and magnesium with diatomaceous earth, a cheap and abundant form of silicon.

When the temperature reached 801 degrees centigrade, the salt melted and absorbed heat in the process. This basic chemical concept – a solid melting into a liquid absorbs heat – kept the nanostructure from collapsing.

The sodium chloride did not contaminate or otherwise affect the reaction, researchers said. Scaling reactions such as this up to larger commercial levels should be feasible, they said.

The study also created, for the first time with this process, nanoporous composite materials of silicon and germanium. These could have wide applications in semiconductors, thermoelectric materials and electrochemical energy devices.

Here’s a link to and a citation for the published paper,

Efficient Fabrication of Nanoporous Si and Si/Ge Enabled by a Heat Scavenger in Magnesiothermic Reactions by Wei Luo, Xingfeng Wang, Colin Meyers, Nick Wannenmacher, Weekit Sirisaksoontorn, Michael M. Lerner & Xiulei Ji. Scientific Reports 3, Article number: 2222 doi:10.1038/srep02222 Published 17 July 2013

This article is open access.

Self-assembling liquid lenses used in optical microscopy to reveal nanoscale objects

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A Jan. 21, 2013 news item on Azonano highlights some research on microscope and self-assembling lenses done at University of California Los Angeles (UCLA),

By using tiny liquid lenses that self-assemble around microscopic objects, a team from UCLA’s Henry Samueli School of Engineering and Applied Science has created an optical microscopy method that allows users to directly see objects more than 1,000 times smaller than the width of a human hair.

Coupled with computer-based computational reconstruction techniques, this portable and cost-effective platform, which has a wide field of view, can detect individual viruses and nanoparticles, making it potentially useful in the diagnosis of diseases in point-of-care settings or areas where medical resources are limited.

The UCLA Jan. 20, 2013 news release, written by Matthew Chin and which originated the news item, explains why another microscopy technique is needed for viewing objects at the nanoscale,

Electron microscopy is one of the current gold standards for viewing nanoscale objects. This technology uses a beam of electrons to outline the shape and structure of nanoscale objects. Other optical imaging–based techniques are used as well, but all of them are relatively bulky, require time for the preparation and analysis of samples, and have a limited field of view — typically smaller than 0.2 square millimeters — which can make viewing particles in a sparse population, such as low concentrations of viruses, challenging.

To overcome these issues, the UCLA team, led by Aydogan Ozcan, an associate professor of electrical engineering and bioengineering, developed the new optical microscopy platform by using nanoscale lenses that stick to the objects that need to be imaged. This lets users see single viruses and other objects in a relatively inexpensive way and allows for the processing of a high volume of samples.
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At scales smaller than 100 nanometers, optical microscopy becomes a challenge because of its weak light-signal levels. Using a special liquid composition, nanoscale lenses, which are typically thinner than 200 nanometers, self-assemble around objects on a glass substrate.

A simple light source, such as a light-emitting diode (LED), is then used to illuminate the nano-lens object assembly. By utilizing a silicon-based sensor array, which is also found in cell-phone cameras, lens-free holograms of the nanoparticles are detected. The holograms are then rapidly reconstructed with the help of a personal computer to detect single nanoparticles on a glass substrate.

The researchers have used the new technique to create images of single polystyrene nanoparticles, as well as adenoviruses and H1N1 influenza viral particles.

While the technique does not offer the high resolution of electron microscopy, it has a much wider field of view — more than 20 square millimeters — and can be helpful in finding nanoscale objects in samples that are sparsely populated.

Here a citation for and a link to the research article,

Wide-field optical detection of nanoparticles using on-chip microscopy and self-assembled nanolenses by Onur Mudanyali, Euan McLeod, Wei Luo, Alon Greenbaum, Ahmet F. Coskun, Yves Hennequin, Cédric P. Allier, & Aydogan Ozcan. Nature Photonics (2013) doi:10.1038/nphoton.2012.337 Published online: 20 January 2013

The article is behind a paywall.