How we transport water in our bodies inspires new water filtration method – from UT Austin

Artificial water channels enable fast and selective water permeation through water-wire networks Credit: Erik Zumalt, Cockrell School of Engineering, The University of Texas at Austin

A multidisciplinary group of engineers and scientists has discovered a new method for water filtration that could have implications for a variety of technologies, such as desalination plants, breathable and protective fabrics, and carbon capture in gas separations. The research team, led by Manish Kumar in the Cockrell School of Engineering at The University of Texas at Austin, published their findings in the latest issue of Nature Nanotechnology.

The study, which brought together researchers from UT Austin, Penn State University, the University of Tennessee, Fudan University and the University of Illinois at Urbana-Champaign, was initially inspired by the way our cells transport water throughout the body and began as an attempt to develop artificial channels for transporting water across membranes. The aim was to mimic aquaporins, essential membrane proteins that serve as water channels and are found in certain cells. Aquaporins are fast and efficient water filtration systems. They form pores in the membranes of cells in various parts of the body—eyes, kidneys and lungs—where water is in greatest demand.

Kumar and the team didn’t manage to mirror the aquaporin system exactly as planned. Instead, they discovered an even more effective water filtration process. Unlike the body’s individual aquaporin cells, which function effectively independent of one another, the membranes developed by Kumar’s research group didn’t work well alone.

But, when he combined several of them to create networks of “water wires,” they were highly effective at water transport and filtration. Water wires are densely connected chains of water molecules that move exceptionally fast, like a train and its individual cars.

“We were trying to copy the already complicated water transport process used by aquaporins and stumbled upon an entirely new, and even better, method,” said Kumar, an associate professor in the Cockrell School’s Department of Civil, Architectural and Environmental Engineering. “It was completely serendipitous. We had no idea it would happen.”

These networks of artificial membranes could prove useful for separating salt from water, a filtration process that is currently inefficient and costly. The new membrane has shown impressive desalination properties, exhibiting far more selective salt and presumably other contaminant removal when compared with existing processes.

“Our method is a thousand times more efficient than current desalination processes in terms of its selectivity and permeability,” Kumar said. “For every 10,000 saltwater molecules that pass through current desalination systems, one salt molecule might not be filtered out. With our new membrane technology, one salt molecule for every 10 million water molecules would not be filtered out, while maintaining a water transport rate comparable to or better than current membranes.”

For his entire career, Kumar has focused on developing materials and processes that take the functionality of biological molecular models and apply them into engineering scales.

“It is difficult to even effectively mimic the complexities of how the human body works, especially at the molecular level,” he said. “This time, however, nature was the starting point for an even greater discovery than we could have ever hoped for.”

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Self-assembling, biomimetic membranes may aid water filtration

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More information: Woochul Song et al, Artificial water channels enable fast and selective water permeation through water-wire networks, Nature Nanotechnology (2019). DOI: 10.1038/s41565-019-0586-8

Journal information: Nature Nanotechnology

Provided by University of Texas at Austin

An Ultra-Thin – Wearable Health Monitor made possible by a ‘Graphene Ink Tattoo’ designed and developed at the University of Texas at Austin

University of Texas at Austin. This is the world’s thinnest wearable Health Monitor, designed and developed by the researchers at the University of Texas at Austin, in the form of a “Graphene-Ink Tattoo”.

Most health monitors in use today are bulky and tend to restrict patients movements. This graphene tattoo will eliminate these restrictions. It picks up electric signal given off by the body and transmits it to a smartphone app.

Watch the Video:

Abstract: Tattoo-like epidermal sensors are an emerging class of truly wearable electronics, owing to their thinness and softness. While most of them are based on thin metal films, a silicon membrane, or nanoparticle-based printable inks, we report sub-micrometer thick, multimodal electronic tattoo sensors that are made of graphene.

The graphene electronic tattoo (GET) is designed as filamentary serpentines and fabricated by a cost- and time-effective “wet transfer, dry patterning” method. It has a total thickness of 463 ± 30 nm, an optical transparency of ∼85%, and a stretchability of more than 40%.

The GET can be directly laminated on human skin just like a temporary tattoo and can fully conform to the microscopic morphology of the surface of skin viajust van der Waals forces. The open-mesh structure of the GET makes it breathable and its stiffness negligible. A bare GET is able to stay attached to skin for several hours without fracture or delamination.

With liquid bandage coverage, a GET may stay functional on the skin for up to several days. As a dry electrode, GET–skin interface impedance is on par with medically used silver/silver-chloride (Ag/AgCl) gel electrodes, while offering superior comfort, mobility, and reliability. GET has been successfully applied to measure electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), skin temperature, and skin hydration.

Read More Here

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Using Nano-Structured conductive Polymer Gels to Improve Lithium-Io Battery’s Performance

 

 

The electrode in lithium-ion (Li-ion) batteries is an integrated system in which both active materials and binder systems play critical roles in determining its final properties. In order to improve battery performance, a lot of research is focusing on the development of high-capacity active materials. However, without an efficient binder system, these novel materials can’t fulfill their potentials.

 

A group of researchers now has contributed to this field from a slight different aspect, developing a high-performance and general binder system for batteries. This entirely new binder system with a nano-architecture promotes both electron and ion transport, which enhances the energy per unit mass and volume of the electrode.This work by Guihua Yu group at University of Texas at Austin and Esther Takeuchi group at Stony Brook University, demonstrates a new generation of nanostructured conductive polymer gel based novel binder materials for fabrication of high-energy lithium-ion battery electrodes.

 

This gel framework could become a next-generation binder system for commercial Li-ion batteries.”Compared to conventional binder system which typically consists of conductive additive and polymer binder, our novel binder plays dual functionalities simultaneously combining conductive and adhesive features, thus greatly improving the better utility of active electrode materials,”Professor Yu tells Nanowerk.

“More importantly, owing to its unique 3D network structure, this gel binder promotes both electron and ion transport in electrode and improves the distribution of active particles, thus enhancing the rate performance and cycle life of battery electrodes.”He points out that this invention is important because it presents a new generation of powerful yet scalable binder materials for lithium ion batteries that show great potential in industrial manufacturing.This novel gel binder can overcome the drawbacks of conventional binder systems, leading to next-generation lithium ion battery with high performance.

The researchers have reported their findings in two papers in Nano Letters (“Nanostructured Conductive Polymer Gels as a General Framework Material To Improve Electrochemical Performance of Cathode Materials in Li-Ion Batteries”) and Advanced Materials (“A Tunable 3D Nanostructured Conductive Gel Framework Electrode for High-Performance Lithium Ion Batteries”).

 

Schematic of synthetic and structural features of commercial lithium iron phosphate (C-LFP)/cross-linked polypyrrole (C-PPy) hybrid gel framework. The conductive polymer chains can be polymerized in situ with electrode materials and cross-linked by molecules with multiple functional groups, resulting in a polymeric network connecting all active particles. (Reprinted with permission by American Chemical Society) (click on image to enlarge)

“A traditional binder system in Li-ion battery electrodes is a binary hybrid with components acting separate functionalities,” explains Yu. “In such system, polymer binders such as polyvinylidene fluoride (PVDF) adhere the active materials and other additives together to hold the mechanical integrity while a conductive additive (usually carbon particles) ensures the conductivity of the entire electrode.”In these electrodes, electrons transport through chains of particles while ions move through the liquid or solid electrolyte that fills the pores of the electrode.

However, the conductive phases are randomly distributed, which may lead to bottlenecks and poor contacts that impede effective access to parts of the battery.And both organic and inorganic components tend to aggregate, which also negatively impact electron and ion transport.The team’s novel conductive gel binder can overcome these drawbacks and thus improve the rate and cyclic performance of Li-ion batteries.

The conductive polymer gels potentially could also be used for responsive/smart electronics such as biosensors, artificial skins and soft robotics.The scientific core of this work is that three-dimensional nanostructured conductive polymer gels can be built up by tunable molecule crosslinking and this unique conductive framework material can promote the electron/ion transport within battery electrodes.

“Firstly, our work provides a new method for synthesis of conductive polymer gel,” elaborates Yu. “Traditionally, conductive polymer gels are synthesized by template-based method, which usually results in low conductivity and poor mechanical properties. The method we developed is to crosslink conductive polymer chains with functional molecules with multiple functional groups, enabling a network, interconnected structure promoting high electronic conductivity and electrochemical activity.”

“Secondly, we demonstrated that this newly developed conductive polymer gel can be used as binder system and significantly improve conventional lithium-ion battery performance owing to their advantageous structural features,” he continues. “The ease of processability and excellent chemical and physical properties of these nanostructured conductive gels enable a new class of binder materials for fabricating next-generation high-energy lithium-ion batteries.”Although the researchers’ binder gel is mechanically strong, it lacks flexibility and stretchability.

The plan is to further modify the mechanical properties by tailoring the molecular backbones of conductive polymers through the addition of side chains or other building block polymers.The scientists further intend to demonstrate the versatility of their gel binders for other important electrode materials, such as some commercial electrode materials, as well as some next-generation ultrahigh-capacity materials, such as silicon, and sulfur.

by Michael Berger @ Nanowerk

Printing Ultrafast Graphene Chips for Flexible Electronics

Futurists are always talking about how flexible electronics will change our lives in amazing ways, but we’ve yet to see anything mind-blowing come to market. A team of scientists from the University of Texas in Austin, however, think they’ve found the key to changing that: ultrafast graphene transistors printed on flexible plastic.

Graphene is amazing. Or at least, it could be. Made from a layer of carbon one-atom thick, it’s the strongest material in the world, it’s… Read…

   9 Incredible Uses for Graphene

Graphene is amazing stuff for a lot different reasons. One reason is that it’s the perfect material for chip-making, and conventional graphene chips have broken several electronic speed records. In the past, however, attempts to put graphene transistors on flexible materials have caused that speed to take a dive. Not with this new method.

Indeed, the chips from Texas clock in at a record-breaking 25-gigahertz. The MIT Technology Review explains the manufacturing process:

To make the transistors, the researchers first fabricate all the non-graphene-containing structures—the electrodes and gates that will be used to switch the transistors on and off—on sheets of plastic. Separately, they grow large sheets of graphene on metal, then peel it off and transfer it to complete the devices. …

The graphene transistors are not only speedy but robust. The devices still work after being soaked in water, and they’re flexible enough to be folded up.

And things are only getting better. Earlier this week we learned about a cutting edge technique for making graphene chips developed by a team of researchers from the University of California.

All we need now is a company to take the plunge and start bringing some of this next level technology to market. And you thought Liquidmetal was cool !!     [Technology Review]

READ MORE …

Scientists Just Figured Out How to Make Lightning-Fast Graphene CPUs

Graphene has the power to change computing forever by making the fastest transistors ever. In theory. We just haven’t figured out how yet. Sound familiar? Fortunately, scientists have just taken a big step closer to making graphene transistors work for real.

Graphene transistors aren’t just fast; they’re lightning fast. The speediest one to date clocked in at some 427 GHz. That’s orders of magnitude more than what you can tease out of today’s processors.  The problem with graphene transistors, though, is that they aren’t particularly good at turning off. They don’t turn off at all actually, which makes it hard to use them as switches.

http://gizmodo.com/scientists-just-figured-out-how-to-make-lightning-fast-1177727488

A new approach to water desalination

Published on Jul  2, 2012

The availability of fresh water is dwindling in many parts of the world, a problem that is expected to grow with populations. One promising source of potable water is the world’s virtually limitless supply of seawater, but so far desalination technology has been too expensive for widespread use.

 

Now, MIT researchers have come up with a new approach using a different kind of filtration material: sheets of graphene, a one-atom-thick form of the element carbon, which they say can be far more efficient and possibly less expensive than existing desalination systems.

Read more at MIT News: http://web.mit.edu/newsoffice/2012/gr…

 

Interface Properties of Graphene Paves Way for New Applications

Researchers from North Carolina State University and the University of Texas have revealed more about graphene’s mechanical properties and demonstrated a technique to improve the stretchability of graphene – developments that should help engineers and designers come up with new technologies that make use of the material.

Graphene is a promising material that is used in technologies such as transparent, flexible electrodes and nanocomposites. And while engineers think graphene holds promise for additional applications, they must first have a better understanding of its mechanical properties, including how it works with other materials.

“This research tells us how strong the interface is between graphene and a stretchable substrate,” says Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and co-author of a paper on the work. “Industry can use that to design new flexible or stretchable electronics and nanocomposites. For example, it tells us how much we can deform the material before the interface between graphene and other materials fails. Our research has also demonstrated a useful approach for making graphene-based, stretchable devices by ‘buckling’ the graphene.”

The researchers looked at how a graphene monolayer – a layer of graphene only one atom thick – interfaces with an elastic substrate. Specifically, they wanted to know how strong the bond is between the two materials because that tells engineers how much strain can be transferred from the substrate to the graphene, which determines how far the graphene can be stretched.

The researchers applied a monolayer of graphene to a polymer substrate, and then stretched the substrate. They used a spectroscopy technique to monitor the strain at various points in the graphene. Strain is a measure of how far a material has stretched.

Initially, the graphene stretched with substrate. However, while the substrate continued to stretch, the graphene eventually began to stretch more slowly and slide on the surface instead. Typically, the edges of the monolayer began to slide first, with the center of the monolayer stretching further than the edges.

“This tells us a lot about the interface properties of the graphene and substrate,” Zhu says. “For the substrate used in this study, polyethylene terephthalate, the edges of the graphene monolayer began sliding after being stretched 0.3 percent of its initial length. But the center continued stretching until the monolayer had been stretched by 1.2 to 1.6 percent.”

The researchers also found that the graphene monolayer buckled when the elastic substrate was returned to its original length. This created ridges in the graphene that made it more stretchable because the material could stretch out and back, like the bellows of an accordion. The technique for creating the buckled material is similar to one developed by Zhu’s lab for creating elastic conductors out of carbon nanotubes.

The paper, “Interfacial Sliding and Buckling of Monolayer Graphene on a Stretchable Substrate,” was published online Aug. 1 in Advanced Functional Materials. Lead author of the paper is Dr. Tao Jiang, a postdoctoral researcher at NC State. The paper was co-authored by Dr. Rui Huang of the University of Texas. The research was funded by the National Science Foundation (NSF) and the NSF’s ASSIST Engineering Research Center at NC State.

-shipman-

Note to Editors: The study abstract follows.

“Interfacial Sliding and Buckling of Monolayer Graphene on a Stretchable Substrate”

Authors: Tao Jiang and Yong Zhu, North Carolina State University; Rui Huang, University of Texas at Austin

Published: Aug. 1 2013, Advanced Functional Materials

Chemists work to desalt the ocean for drinking water, 1 nanoliter at a time

(Nanowerk News) By creating a small electrical field  that removes salts from seawater, chemists at The University of Texas at Austin  and the University of Marburg in Germany have introduced a new method for the  desalination of seawater that consumes less energy and is dramatically simpler  than conventional techniques. The new method requires so little energy that it  can run on a store-bought battery.

The process evades the problems confronting current desalination  methods by eliminating the need for a membrane and by separating salt from water  at a microscale.

The technique, called electrochemically mediated seawater  desalination, was described last week in the journal Angewandte Chemie (“Electrochemically Mediated Seawater  Desalination”). The research team was led by Richard Crooks of The  University of Texas at Austin and Ulrich Tallarek of the University of Marburg.  It’s patent-pending and is in commercial development by startup company Okeanos  Technologies.

The  left panel shows the salt (which is tagged with a fluorescent tracer) flowing  upward after a voltage is applied by an electrode (the dark rectangle) jutting  into the channel at just the point where it branches. In the right panel no  voltage is being applied. (Image: Kyle Knust)

“The availability of water for drinking and crop irrigation is  one of the most basic requirements for maintaining and improving human health,”  said Crooks, the Robert A. Welch Chair in Chemistry in the College of Natural  Sciences. “Seawater desalination is one way to address this need, but most  current methods for desalinating water rely on expensive and easily contaminated  membranes. The membrane-free method we’ve developed still needs to be refined  and scaled up, but if we can succeed at that, then one day it might be possible  to provide fresh water on a massive scale using a simple, even portable,  system.”

This new method holds particular promise for the water-stressed  areas in which about a third of the planet’s inhabitants live. Many of these  regions have access to abundant seawater but not to the energy infrastructure or  money necessary to desalt water using conventional technology. As a result,  millions of deaths per year in these regions are attributed to water-related  causes.

“People are dying because of a lack of freshwater,” said Tony  Frudakis, founder and CEO of Okeanos Technologies. “And they’ll continue to do  so until there is some kind of breakthrough, and that is what we are hoping our  technology will represent.”

To achieve desalination, the researchers apply a small voltage  (3.0 volts) to a plastic chip filled with seawater. The chip contains a  microchannel with two branches. At the junction of the channel an embedded  electrode neutralizes some of the chloride ions in seawater to create an “ion  depletion zone” that increases the local electric field compared with the rest  of the channel. This change in the electric field is sufficient to redirect  salts into one branch, allowing desalinated water to pass through the other  branch.

“The neutralization reaction occurring at the electrode is key  to removing the salts in seawater,” said Kyle Knust, a graduate student in  Crooks’ lab and first author on the paper.

Like a troll at the foot of the bridge, the ion depletion zone  prevents salt from passing through, resulting in the production of freshwater.

Thus far Crooks and his colleagues have achieved 25 percent  desalination. Although drinking water requires 99 percent desalination, they are  confident that goal can be achieved.

“This was a proof of principle,” said Knust. “We’ve made  comparable performance improvements while developing other applications based on  the formation of an ion depletion zone. That suggests that 99 percent  desalination is not beyond our reach.”

The other major challenge is to scale up the process. Right now  the microchannels, about the size of a human hair, produce about 40 nanoliters  of desalted water per minute. To make this technique practical for individual or  communal use, a device would have to produce liters of water per day. The  authors are confident that this can be achieved as well.

If these engineering challenges are surmounted, they foresee a  future in which the technology is deployed at different scales to meet different  needs.

“You could build a disaster relief array or a municipal-scale  unit,” said Frudakis. “Okeanos has even contemplated building a small system  that would look like a Coke machine and would operate in a standalone fashion to  produce enough water for a small village.”

Source: McGill University

Read more: http://www.nanowerk.com/news2/newsid=31072.php#ixzz2XZnuQSxT

Researchers to Study Quantum Metamaterials

Published on October 4, 2012 at 4:34 AM

Through a new Multidisciplinary University Research Initiative (MURI) awarded by the Air Force Office of Scientific Research, researchers from Brown University will lead an effort to study new optical materials and their interactions with light quantum scale. The initiative, titled Quantum Metaphotonics and Quantum Metamaterials, will receive $4.5 million over three years, with a possible two-year extension.

“The field of metamaterials has already expanded the range of optical materials and phenomenon available at larger, classical scales,” said Rashid Zia, Manning assistant professor of engineering and the lead investigator of the initiative. “What we’re doing now is asking what happens when we bring these metamaterials down to the scale of quantum emitters.”

Harnessing the power of light at the quantum scale could clear the way for super-fast optical microprocessors, high-capacity optical memory, securely encrypted communication, and untold other technologies. But before any of these potential applications sees the light of day, there are substantial obstacles to overcome. Not the least of which is the fact that the wavelength of light is larger than quantum-scale objects, limiting the range of possible light-matter interactions.

“The optical wavelength is approximately 100 times larger than a quantum emitter,” Zia said. “So we need to find ways of overcoming this size mismatch to increase interactions at the quantum scale, for example by shrinking the optical wavelength in highly confined metamaterial cavities. And hopefully we can learn something fundamental about the nature of light that opens up news ways of manipulating it to increase these interactions.”

The Quantum Metaphotonics and Metamaterials MURI team includes:

Harry Atwater, California Institute of Technology

Seth Bank, University of Texas at Austin

Mark Brongersma, Stanford University

Nader Engheta, University of Pennsylvania

Shanhui Fan, Stanford University

Nicholas Fang, Massachusetts Institute of Technology

Arto Nurmikko, Brown University

Jelena Vuckovic, Stanford University

Xiang Zhang, University of California, Berkeley

Rashid Zia, Brown University

“It’s really an exciting project,” Zia said. “Over the next five years, this program will bring together 10 groups and 40-plus researchers with complementary expertise to help answer questions that we couldn’t have imagined a short time ago. We are very optimistic about where this will lead.”

Source: http://www.brown.edu/about