Gold foil discovery could lead to wearable technology – Flexibility is the Key


goldfoildiscAn example of a gold foil peeled from single crystal silicon. Credit: Reprinted with permission from Naveen Mahenderkar et al., Science [355]:[1203] (2017).

Some day, your smartphone might completely conform to your wrist, and when it does, it might be covered in pure gold, thanks to researchers at Missouri University of Science and Technology.

Writing in the March 17 issue of the journal Science, the Missouri S&T researchers say they have developed a way to “grow” thin layers of gold on single crystal wafers of silicon, remove the gold foils, and use them as substrates on which to grow other electronic materials.

wearable-textiles-100616-0414_powdes_ti_f1The research team’s discovery could revolutionize wearable or “flexible” technology research, greatly improving the versatility of such electronics in the future.

According to lead researcher Dr. Jay A. Switzer, the majority of research into wearable technology has been done using polymer substrates, or substrates made up of multiple crystals. “And then they put some typically organic semiconductor on there that ends up being flexible, but you lose the order that (silicon) has,” says Switzer, Donald L. Castleman/FCR Endowed Professor of Discovery in Chemistry at S&T.

Because the polymer substrates are made up of multiple crystals, they have what are called , says Switzer. These grain boundaries can greatly limit the performance of an electronic device.

“Say you’re making a solar cell or an LED,” he says. “In a semiconductor, you have electrons and you have holes, which are the opposite of electrons. They can combine at grain boundaries and give off heat. And then you end up losing the light that you get out of an LED, or the current or voltage that you might get out of a solar cell.”

Most electronics on the market are made of silicon because it’s “relatively cheap, but also highly ordered,” Switzer says.

“99.99 percent of electronics are made out of silicon, and there’s a reason – it works great,” he says. “It’s a single crystal, and the atoms are perfectly aligned. But, when you have a single crystal like that, typically, it’s not flexible.”

By starting with single crystal silicon and growing gold foils on it, Switzer is able to keep the high order of silicon on the foil. But because the foil is gold, it’s also highly durable and flexible.

“We bent it 4,000 times, and basically the resistance didn’t change,” he says.

The gold foils are also essentially transparent because they are so thin. According to Switzer, his team has peeled foils as thin as seven nanometers.

Switzer says the challenge his research team faced was not in growing gold on the single crystal silicon, but getting it to peel off as such a thin layer of foil. Gold typically bonds very well to silicon.

“So we came up with this trick where we could photo-electrochemically oxidize the silicon,” Switzer says. “And the gold just slides off.”

Photoelectrochemical oxidation is the process by which light enables a semiconductor material, in this case silicon, to promote a catalytic oxidation reaction.

Switzer says thousands of gold foils—or foils of any number of other metals—can be made from a single crystal wafer of .

The research team’s discovery can be considered a “happy accident.” Switzer says they were looking for a cheap way to make single crystals when they discovered this process.

“This is something that I think a lot of people who are interested in working with highly ordered materials like single crystals would appreciate making really easily,” he says. “Besides making flexible devices, it’s just going to open up a field for anybody who wants to work with .”

Explore further: ‘Nanospears’ could lead to better solar cells, lasers, lighting

More information: Naveen K. Mahenderkar et al. Epitaxial lift-off of electrodeposited single-crystal gold foils for flexible electronics, Science (2017). DOI: 10.1126/science.aam5830

Read more at: https://phys.org/news/2017-03-gold-foil-discovery-wearable-technology.html#jCp

Read more at: https://phys.org/news/2017-03-gold-foil-discovery-wearable-technology.html#jCp

Environmentally-friendly graphene textiles could enable wearable electronics


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Credit: Jiesheng Ren

A new method for producing conductive cotton fabrics using graphene-based inks opens up new possibilities for flexible and wearable electronics, without the use of expensive and toxic processing steps.

Wearable, textiles-based electronics present new possibilities for flexible circuits, healthcare and environment monitoring, energy conversion, and many others. Now, researchers at the Cambridge Graphene Centre (CGC) at the University of Cambridge, working in collaboration with scientists at Jiangnan University, China, have devised a method for depositing graphene-based inks onto cotton to produce a conductive textile. The work, published in the journal Carbon, demonstrates a wearable motion sensor based on the conductive cotton.

Cotton fabric is among the most widespread for use in clothing and textiles, as it is breathable and comfortable to wear, as well as being durable to washing. These properties also make it an excellent choice for textile electronics. A new process, developed by Dr Felice Torrisi at the CGC, and his collaborators, is a low-cost, sustainable and environmentally-friendly method for making conductive cotton textiles by impregnating them with a graphene-based conductive ink.

Based on Dr Torrisi’s work on the formulation of printable graphene inks for flexible electronics, the team created inks of chemically modified graphene flakes that are more adhesive to cotton fibres than unmodified graphene. Heat treatment after depositing the ink on the fabric improves the conductivity of the modified graphene. The adhesion of the modified graphene to the cotton fibre is similar to the way cotton holds coloured dyes, and allows the fabric to remain conductive after several washes.

Although numerous researchers around the world have developed wearable sensors, most of the current wearable technologies rely on rigid electronic components mounted on flexible materials such as plastic films or textiles. These offer limited compatibility with the skin in many circumstances, are damaged when washed and are uncomfortable to wear because they are not breathable. img_0801

“Other conductive inks are made from precious metals such as silver, which makes them very expensive to produce and not sustainable, whereas graphene is both cheap, environmentally-friendly, and chemically compatible with cotton,” explains Dr Torrisi.

 

Co-author Professor Chaoxia Wang of Jiangnan University adds: “This method will allow us to put electronic systems directly into clothes. It’s an incredible enabling technology for smart textiles.”

The work done by Dr Torrisi and Prof Wang, together with students Tian Carey and Jiesheng Ren, opens a number of commercial opportunities for graphene-based inks, ranging from personal health technology, high-performance sportswear, military garments, wearable technology/computing and fashion.
Electron microscopy image of a conductive graphene/cotton fabric. Credit: Jiesheng Ren
Environmentally-friendly graphene textiles could enable wearable electronics

 

“Turning cotton fibres into functional electronic components can open to an entirely new set of applications from healthcare and wellbeing to the Internet of Things,” says Dr Torrisi “Thanks to nanotechnology, in the future our clothes could incorporate these textile-based electronics and become interactive.”

Graphene is carbon in the form of single-atom-thick membranes, and is highly conductive. The group’s work is based on the dispersion of tiny , each less than one nanometre thick, in a water-based dispersion. The individual graphene sheets in suspension are chemically modified to adhere well to the cotton fibres during printing and deposition on the fabric, leading to a thin and uniform conducting network of many graphene sheets. This network of nanometre flakes is the secret to the high sensitivity to strain induced by motion. A simple graphene-coated smart cotton textile used as a wearable strain sensor has been shown to reliably detect up to 500 motion cycles, even after more than 10 washing cycles in normal washing machine.

The use of graphene and other related 2D materials (GRMs) inks to create and devices integrated into fabrics and innovative textiles is at the centre of new technical advances in the smart textiles industry. Dr Torrisi and colleagues at the CGC are also involved in the Graphene Flagship, an EC-funded, pan-European project dedicated to bringing graphene and GRM technologies to commercial applications.

Graphene and GRMs are changing the science and technology landscape with attractive physical properties for electronics, photonics, sensing, catalysis and energy storage. Graphene’s atomic thickness and excellent electrical and mechanical properties give excellent advantages, allowing deposition of extremely thin, flexible and conductive films on surfaces and – with this new method – also on textiles. This combined with the environmental compatibility of graphene and its strong adhesion to cotton make the graphene- strain sensor ideal for wearable applications.

The research was supported by grants from the European Research Council’s Synergy Grant, the International Research Fellowship of the National Natural Science Foundation of China and the Ministry of Science and Technology of China. The technology is being commercialised by Cambridge Enterprise, the University’s commercialisation arm.

Explore further: New study shows nickel graphene can be tuned for optimal fracture strength

More information: Jiesheng Ren et al. Environmentally-friendly conductive cotton fabric as flexible strain sensor based on hot press reduced graphene oxide, Carbon (2017). DOI: 10.1016/j.carbon.2016.10.045

 

Nanotechnology in Smart Textiles and Wearables



The number and variety of smart textiles and wearable electronic devices has increased significantly in the past few years, as they offer significant enhancements to human comfort, health and well-being.

Wearable low-power silicon electronics, light-emitting diodes (LEDs) fabricated on fabrics, textiles with integrated Lithium-ion batteries (LIB) and electronic devices such as smart glasses, watches and lenses have been widely investigated and commercialized (e.g. Google glass, Apple Watch).

There is increasing demand for wearable electronics from industries such as:
Medical and healthcare monitoring and diagnostics.

Sportswear and fitness monitoring (bands).

Consumer electronics such as smart watches, smart glasses and headsets.

Military GPS trackers, equipment (helmets) and wearable robots.

Smart apparel and footwear in fashion and sport.

Workplace safety and manufacturing.

However, improvements in sensors, flexible & printable electronics and energy devices are necessary for wider implementation and nanomaterials and/or their hybrids are enabling the next phase convergence of textiles, electronics and informatics.

They  are opening the way for the integration of electronic components and sensors (e.g. heat and humidity) in high strength, flexible and electrically conductive textiles with energy storage and harvesting capabilities, biological functions, antimicrobial properties, and many other new functionalities.

The industry is now moving towards the development of electronic devices with flexible, thin, and large-area form factors.

Electronic devices that are fabricated on flexible substrates for application in flexible displays, electronic paper, smart packages, skin-like sensors, wearable electronics, implantable medical implements etc. is a fast growing market. Their future development depends greatly on the exploitation of advanced materials. (See Our YouTube Video – below)


Nanomaterials such as carbon nanotubes (CNT), silver nanowires graphene and other 2D materials are viewed as key materials for the future development of wearable electronics for implementation in healthcare and fitness monitoring, electronic devices incorporated into clothing and ‘smart skin’ applications (printed graphene-based sensors integrated with other 2D materials for physiological monitoring).

 


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WEARABLE NANOTECHNOLOGY ~ Imagine Charging Your Phone by “Plugging it Into Your Jacket” …


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Imagine plugging your phone into your jacket to charge it up or recharging your electric car just by leaving it in a sunny parking lot.

Associate Professor Jayan Thomas teaches nanotechnology at the University of Central Florida. He is working on a filament that can store the energy of the sun and could one day be woven into clothing or coat the roof of a car.wearable-textiles-100616-0414_powdes_ti_f1

To demonstrate how his project might work, Thomas had to learn how to use some old technology – a loom.

“Listen-In” to the Audio Link Below

 

Graphene Holds Great Promise for Electronics Applications – Wearable Electronics


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Applications that have really spurred a huge amount of graphene and other two-dimensional (2D) material research over the years have come from the field of electronics. The fear that complementary metal–oxide–semiconductor (CMOS) technology is quickly nearing the end of its ability to ward off Moore’s Law, in which the number of transistors in a dense integrated circuit doubles approximately every two years, has been the spur for much graphene research.

However, there has always been the big problem for graphene that it does not have an intrinsic band gap. It’s a pure conductor and not a semiconductor, like silicon, capable turning on and off the flow of electrons through it. While graphene can be functionalized in a way that it does have a band gap, research for it in the field of electronics have looked outside of digital logic where an intrinsic band gap is such an advantage.

In the stories below, we see how graphene’s unrivaled conductivity is being exploited to take advantage of its strengths rather than trying to cover up for its weaknesses.

Graphene Comes to the Rescue of Li-ion Batteries

The role of graphene in increasing the charge capacity of the electrodes in lithium-ion (Li-ion) batteries has varied. There’s been “decorated graphene” in which nanoparticles are scattered across the surface of the graphene, and graphene nanoribbons, just to name a few of the avenues that have been pursued.

Another way in which graphene has been looked at is to better enable silicon to serve as the electrode material for Li-ion batteries. Silicon is a great material for increasing the storage capacity of electrodes in Li-ion batteries, but there’s one big problem: it cracks after just few charge/discharge cycles. The aim has been to find a way to make silicon so that it’s not so brittle and can withstand the swelling and shrinking during the charge charging and discharing of lithium atoms into the electrode material In these efforts, like those out Northwestern University, the role of graphene has been to sandwich silicon between layers graphene sheets in the anode of the battery.

Now, Yi Cui from both Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory, who has been at the forefront of research to get silicon to be more flexible and durable for Li-ion batteries, has turned to graphene to solve the issue.

Cui and his colleagues were able to demonstrate in research described in the journal Nature Energy, a method for to encasing each particle of silicon in a cage of graphene that enables the silicon to expand and contract without cracking. In a full-cell electrochemical test, the graphene-infused silicon anodes retained 90 percent of their charge capacity after 100 charge-discharge cycles.

Previous attempts by Cui and many others to create nanostructured silicon has been very difficult, making mass production fairly impractical. However, based on these latest results, Cui believes that this approach is not only technologically possible, but may in fact be commercially viable.

The process involves coating the silicon particles with a layer of nickel. The nickel coating is used as the surface and the catalyst for the second step: growing the graphene. The final step of the process involves using an acid on the graphene-coated silicon particles so that the nickel is etched away.

“This new method allows us to use much larger silicon particles that are one to three microns, or millionths of a meter, in diameter, which are cheap and widely available,” Cui said in a press release. “Particles this big have never performed well in battery anodes before, so this is a very exciting new achievement, and we think it offers a practical solution.”

While a practical manufacturing approach was much needed, the technique also leads to an electrode material with very high charge capacity.

“Researchers have tried a number of other coatings for silicon anodes, but they all reduced the anode’s efficiency,” said Stanford postdoctoral researcher Kai Yan, in a press release. “The form-fitting graphene cages are the first coating that maintains high efficiency, and the reactions can be carried out at relatively low temperatures.”

Graphene Provides the Perfect Touch to Flexible Sensors

 

Photo: Someya Laboratory

Flexible sensors are the technological backbone of artificial skin technologies. The idea is that you can impart the sense of touch to a flexible sensor, making it possible to cover a prosthetic device for either a robot or replacement limb so it can feel. Creating materials that tick the boxes of flexibility, durability and sensitivity has been a challenge. Over the years, researchers have increasingly turned to nanomaterials, and graphene in particular, as a possible solution.

Researchers at the University of Tokyo have found that nanofibers produced from a combination of carbon nanotubes and graphene overcomes some of the big problems facing flexible pressure sensors: they’re not that accurate after being bent or deformed. The researchers have suggested that the flexible sensor they have developed could provide a more accurate detection breast cancer.

In research described in the journal Nature Nanotechnology, the scientists produced their flexible sensor by employing organic transistors and a pressure sensitive nanofiber structure.

The researchers constructed the nanofiber structure using nanofibers with diameters ranging between 300 to 700 nanometers. The researchers produced the nanofibers by combining carbon nanotubes and graphene and mixing that into a flexible polymer. The nanofibers entangled with each other to form a thin, transparent structure.

In contrast to other flexible sensors in which the striving for accuracy makes the sensors too sensitive to being deformed in any way, the fibers in this new flexible sensor does not lose their accuracy in measuring pressures. These fibers achieve this because of their ability to change their relative alignment to accommodate the bending. This allows them to continue measuring pressure because it reduces the strain in individual fibers.

Tunable Graphene Plasmons Lead to Tunable Lasers

Illustration: University of Manchester

A few years ago, researchers found that the phenomenon that occurs when photons strike a metallic surface and stir up the movement of electrons on the surface to the point where the electrons form into waves—known as surface plasmons—also occurs in graphene.

This discovery along with the ability to tune the graphene plasmons has been a big boon for the use of graphene in optoelectronic applications.  Now research out of the University of Manchester, led by Konstantin Novoselov, who along with Andre Geim were the two University of Manchester scientists who won the Nobel Prize for discovering graphene, has leveraged the ability of tuning graphene plasmons and combined it with terahertz quantum cascade lasers, making it possible to reversibly alter their emission.

This ability to reversibly the alter the emission of quantum cascade lasers is a big deal in optoelectronic applicatiopns, such as fiber optics telecommunication technologies by offering potentially higher bandwidth capabilities.

“Current terahertz devices do not allow for tunable properties, a new device would have to be made each time requirements changed, making them unattractive on an industrial scale,” said Novoselov in a press release. “Graphene however, can allow for terahertz devices to be switched on and off, as well as altering their state.”

In research described in the journal Science, were able to manipulate the doping levels of a graphene sheet so that it generated plasmons on its surface. When this doped graphene sheet was combined with a terahertz quantum cascade laser, it became possible to tune the transmission of the laser by tuning the graphene plasmons, essentially changing the concentration of charge carriers.

Graphene Flakes Speed Up Artificial Brains

Illustration: Alexey Kotelnikov/Alamy
Researchers out of Princeton University have found that graphene flakes could be a key feature in computer chips that aim at mimicking the function of the human brain.
In the human brain, neurons are used to transmit information by passing electrical charges through them. In artificial brains, transistors would take the place of neurons. One approach has been to construct the transistors out of lasers that would turn and off and the time intervals between the on and off states of the lasers would represent the 1s and 0s of digital logic.

One of the challenges that researchers have faced in this design is getting the time intervals between the laser pulses down to picosecond time scales, one trillionth of a second.

In research described in the journal Nature Scientific Reports, the Princeton researchers placed graphene flakes inside a semiconductor laser to act as a kind of “saturable absorber,” that absorbed photons and then was able to emit them in a quick burst.

It turns out graphene possesses a number of properties that makes it attractive for this application. Not only can it absorb and release photons extremely quickly, but it can also work at any wavelength. What this means is that even if semiconductor lasers are emitting different colors, the graphene makes it possible for them to work together simultaneously without interfering with each other, leading to higher processing speeds.

Posted By Terrance Barkan 

Defining “Nanotechnology” And … A New Energy Storage Company Comes of Age – Tenka Energy, LLC – Developing the Next Generation of Super Capacitors and Batteries


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“A New Energy Storage Company Comes of Age.” 

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Defining Nanotechnology

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Can you define nanotechnology? Although the term has circulated since the 1980s, there are still several misconceptions about the field and what it entails.

 

Perhaps that’s because how we define nanotechnology has evolved over the years and there’s still no widespread agreement.

 

In fact, the inaugural issue of Nature Nanotechnology, published in 2006, includeda feature in which numerous researchers attempted to map the subject’s parameters. One participant even predicted that the term would fall out of use within the decade!

But here we are, ten years later—and the term remains very much in play. As for the question of how to define nanotechnology? That’s still up for debate too.

 

A Standard Definition

Researchers can agree on some things: nanotechnology involves structures, devices or materials that are both manmade and very, very small. (“Great Things from Small Things”) But that’s where the consensus ends.

Most experts consider ‘very, very small’ to in this case refer to materials shorter than 100 nanometers (nm) in length. For context, a single strand of human hair is 80,000 nm wide.

Some scientists, however, find such a hard and fast definition unhelpful. They argue that a strict one to 100 nm range excludes several materials, particularly pharmaceutical ones, that rightfully fall within the nanotechnology realm. These materials still have special properties that result specifically from their nanoscale—such as increased magnetism or conductivity.

In fact, that’s the key to defining nanotechnology. Matter takes on different properties at nanoscale than it does in its other forms or sizes—and that allows researchers to manipulate or engineer it in unprecedented ways.

When it comes to a working definition, the American National Nanotechnology Initiative says it best. According to their website,“Nanotechnology is the understanding and control of matter at the nanoscale, at dimensions betweenapproximately 1 and 100 nanometers, where unique phenomena enable novel applications.”

 

A Big Impact for Life Science

But thinking in nanometers doesn’t necessarily mean thinking small. Despite the scale of the materials, nanotechnology can and does have a big impact—particularly when it comes to its applications in life scienceNano Body II 43a262816377a448922f9811e069be13

Perhaps that’s why companies like Merck (NYSE:MRK) continue to invest in nanotechnology. Emend, Merck’s anti-nausea drug for chemotherapy patients, is formulated as NanoCrystal drug particles.

Meanwhile, Pfizer (NYSE:PFE) recently bought the assets of Bind Therapeutics, a nanotech drug company. The Wall Street Journal reportedthat Pfizer will continue Bind Therapeutics’ work developing nanoparticle oncology drugs.

Nanotechnology has applications beyond pharmaceuticals, too. Several medical devices, including burn dressings, surgical mesh and a laparoscopic vessel fusion system all use nanotechnology. And over in the biotech space, it can even be used to engineer tissue.

 

Future Applications

Nanotechnology has more life science applications on the horizon. Nanorobots might one day detect the presence of cancerous cells, or seek out bacteria in the bloodstream. Nanoparticles could be used in drug delivery, targeting treatments to affected cells.

It may sound like the stuff of science fiction, but nanotechnology is making such developments possible. Indeed, its applications in healthcare are a major reason why the nanotechnology market is growing. A reportfrom Global Industry Analysts projects the global nanotech market to reach US$7.8 billion by 2020—just four short years from now.

With that timeline in mind, life science investors may consider investigating nanotechnology now. After all, such securities are usually a long term investment—and for the patient, savvy investor, the potential pay-offs could be huge.

 

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