Tag Archives: Kostya S. Novoselov

Study rare physics with electrically tunable graphene devices

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An April 7, 2022 news item on Nanowerk announces graphene research that could lead to advances in optoelectronics (Note: Links have been removed),

An international team, co-led by researchers at The University of Manchester’s National Graphene Institute (NGI) in the UK and the Penn State [Pennsylvania State University] College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points.

The team published their results in Science (“Topological engineering of terahertz light using electrically tuneable exceptional point singularities”).

The work could advance optoelectronic technologies to better generate, control and sense light and potentially communications, according to the researchers. They demonstrated a way to control THz waves, which exist at frequencies between those of microwaves and infrared waves. The feat could contribute to the development of ‘beyond-5G’ wireless technology for high-speed communication networks.

…

An April 8, 2022 University of Manchester press release (also on EurekAlert but published on April 7, 2022) delves further into the research,

Weak and strong interactions

Light and matter can couple, interacting at different levels: weakly, where they might be correlated but do not change each other’s constituents; or strongly, where their interactions can fundamentally change the system. The ability to control how the coupling shifts from weak to strong and back again has been a major challenge to advancing optoelectronic devices — a challenge researchers have now solved.

“We have demonstrated a new class of optoelectronic devices using concepts of topology — a branch of mathematics studying properties of geometric objects,” said co-corresponding author Coskun Kocabas, professor of 2D device materials at The University of Manchester. “Using exceptional point singularities, we show that topological concepts can be used to engineer optoelectronic devices that enable new ways to manipulate terahertz light.”

Kocabas is also affiliated with the Henry Royce Institute for Advanced Materials, headquartered in Manchester.

Exceptional points are spectral singularities — points at which any two spectral values in an open system coalesce. They are, unsurprisingly, exceptionally sensitive and respond to even the smallest changes to the system, revealing curious yet desirable characteristics, according to co-corresponding author Şahin K. Özdemir, associate professor of engineering science and mechanics at Penn State.

“At an exceptional point, the energy landscape of the system is considerably modified, resulting in reduced dimensionality and skewed topology,” said Özdemir, who is also affiliated with the Materials Research Institute, Penn State. “This, in turn, enhances the system’s response to perturbations, modifies the local density of states leading to the enhancement of spontaneous emission rates and leads to a plethora of phenomena. Control of exceptional points, and the physical processes that occur at them, could lead to applications for better sensors, imaging, lasers and much more.”

Platform composition

The platform the researchers developed consists of a graphene-based tunable THz resonator, with a gold-foil gate electrode forming a bottom reflective mirror. Above it, a graphene layer is book-ended with electrodes, forming a tunable top mirror. A non-volatile ionic liquid electrolyte layer sits between the mirrors, enabling control of the top mirror’s reflectivity by changing the applied voltage. In the middle of the device, between the mirrors, are molecules of alpha lactose, a sugar commonly found in milk.  

The system is controlled by two adjusters. One raises the lower mirror to change the length of the cavity — tuning the frequency of resonation to couple the light with the collective vibrational modes of the organic sugar molecules, which serve as a fixed number of oscillators for the system. The other adjuster changes the voltage applied to the top graphene mirror — altering the graphene’s reflective properties to transition the energy loss imbalances to adjust coupling strength. The delicate, fine tuning shifts weakly coupled terahertz light and organic molecules to become strongly coupled and vice versa.

“Exceptional points coincide with the crossover point between the weak and strong coupling regimes of terahertz light with collective molecular vibrations,” Özdemir said.

He noted that these singularity points are typically studied and observed in the coupling of analogous modes or systems, such as two optical modes, electronic modes or acoustic modes.

“This work is one of rare cases where exceptional points are demonstrated to emerge in the coupling of two modes with different physical origins,” Kocabas said. “Due to the topology of the exceptional points, we observed a significant modulation in the magnitude and phase of the terahertz light, which could find applications in next-generation THz communications.”

Unprecedented phase modulation in the THz spectrum

As the researchers apply voltage and adjust the resonance, they drive the system to an exceptional point and beyond. Before, at and beyond the exceptional point, the geometric properties — the topology — of the system change.

One such change is the phase modulation, which describes how a wave changes as it propagates and interacts in the THz field. Controlling the phase and amplitude of THz waves is a technological challenge, the researchers said, but their platform demonstrates unprecedented levels of phase modulation. The researchers moved the system through exceptional points, as well as along loops around exceptional points in different directions, and measured how it responded through the changes. Depending on the system’s topology at the point of measurement, phase modulation could range from zero to four magnitudes larger.

“We can electrically steer the device through an exceptional point, which enables electrical control on reflection topology,” said first author M. Said Ergoktas. “Only by controlling the topology of the system electronically could we achieve these huge modulations.” 

According to the researchers, the topological control of light-matter interactions around an exceptional point enabled by the graphene-based platform has potential applications ranging from topological optoelectronic and quantum devices to topological control of physical and chemical processes.

Contributors include Kaiyuan Wang, Gokhan Bakan, Thomas B. Smith, Alessandro Principi and Kostya S. Novoselov, University of Manchester; Sina Soleymani, graduate student in the Penn State Department of Engineering Science and Mechanics; Sinan Balci, Izmir Institute of Technology, Turkey; Nurbek Kakenov, who conducted work for this paper while at Bilkent University, Turkey.

I love the language in this press release, especially, ‘spectral singularities’. The explanations are more appreciated and help to make this image more than a pretty picture,

Caption: An international team, co-led by researchers at The University of Manchester’s National Graphene Institute (NGI) in the UK and the Penn State College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points. The feat could contribute to the development of beyond-5G wireless technology for high-speed communication networks. Credit: Image Design, Pietro Steiner, The University of Manchester

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

Topological engineering of terahertz light using electrically tunable exceptional point singularities by M. Said Ergoktas, Sina Soleymani, Nurbek Kakenov, Kaiyuan Wang, Thomas B. Smith, Gokhan Bakan, Sinan Balci, Alessandro Principi, Kostya S. Novoselov, Sahin K. Ozdemir, and Coskun Kocabas. Science • 7 Apr 2022 • Vol 376, Issue 6589 • pp. 184-188 • DOI: 10.1126/science.abn6528

This paper is behind a paywall.

Oddly, there is an identical press release dated April 8, 2022 on the Pennsylvania State University website with a byline for By Ashley J. WennersHerron and Alan Beck. Interestingly the first author is from Penn State and the second author is from the University of Manchester.

Regulating body temperature, graphene-style

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I find some illustrations a little difficult to decipher,

Caption: Graphene thermal smart materials. Credit: The University of Manchester

I believe the red in the ‘on/off’ images, signifies heat from the surrounding environment and is not an indicator for body heat and the yellow square in the ‘on’ image indicates the shirt is working and repelling that heat.

Moving on, a June 18, 2020 news item on Nanowerk describes this latest work on a smart textile that can help regulate body temperature when it’s hot,

New research on the two-dimensional (2D) material graphene has allowed researchers to create smart adaptive clothing which can lower the body temperature of the wearer in hot climates.

A team of scientists from The University of Manchester’s National Graphene Institute have created a prototype garment to demonstrate dynamic thermal radiation control within a piece of clothing by utilising the remarkable thermal properties and flexibility of graphene. The development also opens the door to new applications such as, interactive infrared displays and covert infrared communication on textiles.

A June 18, 2020 University of Manchester press release (also on EurekAlert), which originated the news item, provides more detail,

The human body radiates energy in the form of electromagnetic waves in the infrared spectrum (known as blackbody radiation). In a hot climate it is desirable to make use the full extent of the infrared radiation to lower the body temperature that can be achieved by using infrared-transparent textiles. As for the opposite case, infrared-blocking covers are ideal to minimise the energy loss from the body. Emergency blankets are a common example used to deal with treating extreme cases of body temperature fluctuation.

The collaborative team of scientists demonstrated the dynamic transition between two opposite states by electrically tuning the infrared emissivity (the ability to radiate energy) of the graphene layers integrated onto textiles.

One-atom thick graphene was first isolated and explored in 2004 at The University of Manchester. Its potential uses are vast and research has already led to leaps forward in commercial products including; batteries, mobile phones, sporting goods and automotive.

The new research published today in journal Nano Letters, demonstrates that the smart optical textile technology can change its thermal visibility. The technology uses graphene layers to control of thermal radiation from textile surfaces.

Professor Coskun Kocabas, who led the research, said: “Ability to control the thermal radiation is a key necessity for several critical applications such as temperature management of the body in excessive temperature climates. Thermal blankets are a common example used for this purpose. However, maintaining these functionalities as the surroundings heats up or cools down has been an outstanding challenge.”

Prof Kocabas added: “The successful demonstration of the modulation of optical properties on different forms of textile can leverage the ubiquitous use of fibrous architectures and enable new technologies operating in the infrared and other regions of the electromagnetic spectrum for applications including textile displays, communication, adaptive space suits, and fashion”.

This study built on the same group’s previous research using graphene to create thermal camouflage which would fool infrared cameras. The new research can also be integrated into existing mass-manufacture textile materials such as cotton. To demonstrate, the team developed a prototype product within a t-shirt allowing the wearer to project coded messages invisible to the naked eye but readable by infrared cameras.

“We believe that our results are timely showing the possibility of turning the exceptional optical properties of graphene into novel enabling technologies. The demonstrated capabilities cannot be achieved with conventional materials.”

“The next step for this area of research is to address the need for dynamic thermal management of earth-orbiting satellites. Satellites in orbit experience excesses of temperature, when they face the sun, and they freeze in the earth’s shadow. Our technology could enable dynamic thermal management of satellites by controlling the thermal radiation and regulate the satellite temperature on demand.” said Kocabas.

Professor Sir Kostya Novoselov was also involved in the research: “This is a beautiful effect, intrinsically routed in the unique band structure of graphene. It is really exciting to see that such effects give rise to the high-tech applications.” he said.

Advanced materials is one of The University of Manchester’s research beacons – examples of pioneering discoveries, interdisciplinary collaboration and cross-sector partnerships that are tackling some of the biggest questions facing the planet. #ResearchBeacons

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

Graphene-Enabled Adaptive Infrared Textiles by M. Said Ergoktas, Gokhan Bakan, Pietro Steiner, Cian Bartlam, Yury Malevich, Elif Ozden-Yenigun, Guanliang He, Nazmul Karim, Pietro Cataldi, Mark A. Bissett, Ian A. Kinloch, Kostya S. Novoselov, and Coskun Kocabas. Nano Lett. 2020, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acs.nanolett.0c01694 Publication Date:June 18, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Creating quantum dots (artificial atoms) in graphene

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An Aug. 22, 2016 news item on phys.org describes some recent work on artificial atoms and graphene from the Technical University of Vienna (Austria) and partners in Germany and the UK,

In a tiny quantum prison, electrons behave quite differently as compared to their counterparts in free space. They can only occupy discrete energy levels, much like the electrons in an atom – for this reason, such electron prisons are often called “artificial atoms”. Artificial atoms may also feature properties beyond those of conventional ones, with the potential for many applications for example in quantum computing. Such additional properties have now been shown for artificial atoms in the carbon material graphene. The results have been published in the journal Nano Letters, the project was a collaboration of scientists from TU Wien (Vienna, Austria), RWTH Aachen (Germany) and the University of Manchester (GB).

“Artificial atoms open up new, exciting possibilities, because we can directly tune their properties”, says Professor Joachim Burgdörfer (TU Wien, Vienna). In semiconductor materials such as gallium arsenide, trapping electrons in tiny confinements has already been shown to be possible. These structures are often referred to as “quantum dots”. Just like in an atom, where the electrons can only circle the nucleus on certain orbits, electrons in these quantum dots are forced into discrete quantum states.

Even more interesting possibilities are opened up by using graphene, a material consisting of a single layer of carbon atoms, which has attracted a lot of attention in the last few years. “In most materials, electrons may occupy two different quantum states at a given energy. The high symmetry of the graphene lattice allows for four different quantum states. This opens up new pathways for quantum information processing and storage” explains Florian Libisch from TU Wien. However, creating well-controlled artificial atoms in graphene turned out to be extremely challenging.

Florian Libisch, explaining the structure of graphene. Courtesy Technical University of Vienna

Florian Libisch, explaining the structure of graphene. Courtesy Technical University of Vienna

An Aug. 22, 2016 Technical University of Vienna press release (also on EurekAlert), which originated the news item, provides more detail,

There are different ways of creating artificial atoms: The simplest one is putting electrons into tiny flakes, cut out of a thin layer of the material. While this works for graphene, the symmetry of the material is broken by the edges of the flake which can never be perfectly smooth. Consequently, the special four-fold multiplicity of states in graphene is reduced to the conventional two-fold one.

Therefore, different ways had to be found: It is not necessary to use small graphene flakes to capture electrons. Using clever combinations of electrical and magnetic fields is a much better option. With the tip of a scanning tunnelling microscope, an electric field can be applied locally. That way, a tiny region is created within the graphene surface, in which low energy electrons can be trapped. At the same time, the electrons are forced into tiny circular orbits by applying a magnetic field. “If we would only use an electric field, quantum effects allow the electrons to quickly leave the trap” explains Libisch.

The artificial atoms were measured at the RWTH Aachen by Nils Freitag and Peter Nemes-Incze in the group of Professor Markus Morgenstern. Simulations and theoretical models were developed at TU Wien (Vienna) by Larisa Chizhova, Florian Libisch and Joachim Burgdörfer. The exceptionally clean graphene sample came from the team around Andre Geim and Kostya Novoselov from Manchester (GB) – these two researchers were awarded the Nobel Prize in 2010 for creating graphene sheets for the first time.

The new artificial atoms now open up new possibilities for many quantum technological experiments: “Four localized electron states with the same energy allow for switching between different quantum states to store information”, says Joachim Burgdörfer. The electrons can preserve arbitrary superpositions for a long time, ideal properties for quantum computers. In addition, the new method has the big advantage of scalability: it should be possible to fit many such artificial atoms on a small chip in order to use them for quantum information applications.

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

Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings by Nils M. Freitag, Larisa A. Chizhova, Peter Nemes-Incze, Colin R. Woods, Roman V. Gorbachev, Yang Cao, Andre K. Geim, Kostya S. Novoselov, Joachim Burgdörfer, Florian Libisch, and Markus Morgenstern. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.6b02548 Publication Date (Web): July 28, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Dexter Johnson in an Aug. 23, 2016 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides some additional insight into the world of quantum dots,

Quantum dots made from semiconductor materials, like silicon, are beginning to transform the display market. While it is their optoelectronic properties that are being leveraged in displays, the peculiar property of quantum dots that allows their electrons to be forced into discrete quantum states has long held out the promise of enabling quantum computing.

If you have time to read it, Dexter’s post features an email interview with Florian Libisch where they further discuss quantum dots and quantum computing.

Wearable tech for Christmas 2015 and into 2016

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This is a roundup post of four items to cross my path this morning (Dec. 17, 2015), all of them concerned with wearable technology.

The first, a Dec. 16, 2015 news item on phys.org, is a fluffy little piece concerning the imminent arrival of a new generation of wearable technology,

It’s not every day that there’s a news story about socks. But in November [2015], a pair won the Best New Wearable Technology Device Award at a Silicon Valley conference. The smart socks, which track foot landings and cadence, are at the forefront of a new generation of wearable electronics, according to an article in Chemical & Engineering News (C&EN), the weekly newsmagazine of the American Chemical Society [ACS].

That news item was originated by a Dec. 16, 2015 ACS news release on EurekAlert which adds this,

Marc S. Reisch, a senior correspondent at C&EN, notes that stiff wristbands like the popular FitBit that measure heart rate and the number of steps people take have become common. But the long-touted technology needed to create more flexible monitoring devices has finally reached the market. Developers have successfully figured out how to incorporate stretchable wiring and conductive inks in clothing fabric, program them to transmit data wirelessly and withstand washing.

In addition to smart socks, fitness shirts and shoe insoles are on the market already or are nearly there. Although athletes are among the first to gain from the technology, the less fitness-oriented among us could also benefit. One fabric concept product — designed not for covering humans but a car steering-wheel — could sense driver alertness and make roads safer.

Reisch’s Dec. 7, 2015 article (C&EN vol. 93, issue 48, pp. 28-90) provides more detailed information and market information such as this,

Materials suppliers, component makers, and apparel developers gathered at a printed-electronics conference in Santa Clara, Calif., within a short drive of tech giants such as Google and Apple, to compare notes on embedding electronics into the routines of daily life. A notable theme was the effort to stealthily [emphasis mine] place sensors on exercise shirts, socks, and shoe soles so that athletes and fitness buffs can wirelessly track their workouts and doctors can monitor the health of their patients.

“Wearable technology is becoming more wearable,” said Raghu Das, chief executive officer of IDTechEx [emphasis mine], the consulting firm that organized the conference. By that he meant the trend is toward thinner and more flexible devices that include not just wrist-worn fitness bands but also textiles printed with stretchable wiring and electronic sensors, thanks to advances in conductive inks.

Interesting use of the word ‘stealthy’, which often suggests something sneaky as opposed to merely secretive. I imagine what’s being suggested is that the technology will not impose itself on the user (i.e., you won’t have to learn how to use it as you did with phones and computers).

Leading into my second item, IDC (International Data Corporation), not to be confused with IDTechEx, is mentioned in a Dec. 17, 2015 news item about wearable technology markets on phys.org,

The global market for wearable technology is seeing a surge, led by watches, smart clothing and other connected gadgets, a research report said Thursday [Dec. 16, 2015].

IDC said its forecast showed the worldwide wearable device market will reach a total of 111.1 million units in 2016, up 44.4 percent from this year.

By 2019, IDC sees some 214.6 million units, or a growth rate averaging 28 percent.

A Dec. 17, 2015 IDC press release, which originated the news item, provides more details about the market forecast,

“The most common type of wearables today are fairly basic, like fitness trackers, but over the next few years we expect a proliferation of form factors and device types,” said Jitesh Ubrani , Senior Research Analyst for IDC Mobile Device Trackers. “Smarter clothing, eyewear, and even hearables (ear-worn devices) are all in their early stages of mass adoption. Though at present these may not be significantly smarter than their analog counterparts, the next generation of wearables are on track to offer vastly improved experiences and perhaps even augment human abilities.”

One of the most popular types of wearables will be smartwatches, reaching a total of 34.3 million units shipped in 2016, up from the 21.3 million units expected to ship in 2015. By 2019, the final year of the forecast, total shipments will reach 88.3 million units, resulting in a five-year CAGR of 42.8%.

“In a short amount of time, smartwatches have evolved from being extensions of the smartphone to wearable computers capable of communications, notifications, applications, and numerous other functionalities,” noted Ramon Llamas , Research Manager for IDC’s Wearables team. “The smartwatch we have today will look nothing like the smartwatch we will see in the future. Cellular connectivity, health sensors, not to mention the explosive third-party application market all stand to change the game and will raise both the appeal and value of the market going forward.

“Smartwatch platforms will lead the evolution,” added Llamas. “As the brains of the smartwatch, platforms manage all the tasks and processes, not the least of which are interacting with the user, running all of the applications, and connecting with the smartphone. Once that third element is replaced with cellular connectivity, the first two elements will take on greater roles to make sense of all the data and connections.”

Top Five Smartwatch Platform Highlights

Apple’s watchOS will lead the smartwatch market throughout our forecast, with a loyal fanbase of Apple product owners and a rapidly growing application selection, including both native apps and Watch-designed apps. Very quickly, watchOS has become the measuring stick against which other smartwatches and platforms are compared. While there is much room for improvement and additional features, there is enough momentum to keep it ahead of the rest of the market.

Android/Android Wear will be a distant second behind watchOS even as its vendor list grows to include technology companies (ASUS, Huawei, LG, Motorola, and Sony) and traditional watchmakers (Fossil and Tag Heuer). The user experience on Android Wear devices has been largely the same from one device to the next, leaving little room for OEMs to develop further and users left to select solely on price and smartwatch design.

Smartwatch pioneer Pebble will cede market share to AndroidWear and watchOS but will not disappear altogether. Its simple user interface and devices make for an easy-to-understand use case, and its price point relative to other platforms makes Pebble one of the most affordable smartwatches on the market.

Samsung’s Tizen stands to be the dark horse of the smartwatch market and poses a threat to Android Wear, including compatibility with most flagship Android smartphones and an application selection rivaling Android Wear. Moreover, with Samsung, Tizen has benefited from technology developments including a QWERTY keyboard on a smartwatch screen, cellular connectivity, and new user interfaces. It’s a combination that helps Tizen stand out, but not enough to keep up with AndroidWear and watchOS.

There will be a small, but nonetheless significant market for smart wristwear running on a Real-Time Operating System (RTOS), which is capable of running third-party applications, but not on any of these listed platforms. These tend to be proprietary operating systems and OEMs will use them when they want to champion their own devices. These will help within specific markets or devices, but will not overtake the majority of the market.

The company has provided a table with five-year CAGR (compound annual growth rate) growth estimates, which can be found with the Dec. 17, 2015 IDC press release.

Disclaimer: I am not endorsing IDC’s claims regarding the market for wearable technology.

For the third and fourth items, it’s back to the science. A Dec. 17, 2015 news item on Nanowerk, describes, in general terms, some recent wearable technology research at the University of Manchester (UK), Note: A link has been removed),

Cheap, flexible, wireless graphene communication devices such as mobile phones and healthcare monitors can be directly printed into clothing and even skin, University of Manchester academics have demonstrated.

In a breakthrough paper in Scientific Reports (“Highly Flexible and Conductive Printed Graphene for Wireless Wearable Communications Applications”), the researchers show how graphene could be crucial to wearable electronic applications because it is highly-conductive and ultra-flexible.

The research could pave the way for smart, battery-free healthcare and fitness monitoring, phones, internet-ready devices and chargers to be incorporated into clothing and ‘smart skin’ applications – printed graphene sensors integrated with other 2D materials stuck onto a patient’s skin to monitor temperature, strain and moisture levels.

Detail is provided in a Dec. 17, 2015 University of Manchester press release, which originated the news item, (Note: Links have been removed),

Examples of communication devices include:

• In a hospital, a patient wears a printed graphene RFID tag on his or her arm. The tag, integrated with other 2D materials, can sense the patient’s body temperature and heartbeat and sends them back to the reader. The medical staff can monitor the patient’s conditions wirelessly, greatly simplifying the patient’s care.

• In a care home, battery-free printed graphene sensors can be printed on elderly peoples’ clothes. These sensors could detect and collect elderly people’s health conditions and send them back to the monitoring access points when they are interrogated, enabling remote healthcare and improving quality of life.

Existing materials used in wearable devices are either too expensive, such as silver nanoparticles, or not adequately conductive to have an effect, such as conductive polymers.

Graphene, the world’s thinnest, strongest and most conductive material, is perfect for the wearables market because of its broad range of superlative qualities. Graphene conductive ink can be cheaply mass produced and printed onto various materials, including clothing and paper.

“Sir Kostya Novoselov

To see evidence that cheap, scalable wearable communication devices are on the horizon is excellent news for graphene commercial applications.

Sir Kostya Novoselov (tweet)„

The researchers, led by Dr Zhirun Hu, printed graphene to construct transmission lines and antennas and experimented with these in communication devices, such as mobile and Wifi connectivity.

Using a mannequin, they attached graphene-enabled antennas on each arm. The devices were able to ‘talk’ to each other, effectively creating an on-body communications system.

The results proved that graphene enabled components have the required quality and functionality for wireless wearable devices.

Dr Hu, from the School of Electrical and Electronic Engineering, said: “This is a significant step forward – we can expect to see a truly all graphene enabled wireless wearable communications system in the near future.

“The potential applications for this research are huge – whether it be for health monitoring, mobile communications or applications attached to skin for monitoring or messaging.

“This work demonstrates that this revolutionary scientific material is bringing a real change into our daily lives.”

Co-author Sir Kostya Novoselov, who with his colleague Sir Andre Geim first isolated graphene at the University in 2004, added: “Research into graphene has thrown up significant potential applications, but to see evidence that cheap, scalable wearable communication devices are on the horizon is excellent news for graphene commercial applications.”

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

Highly Flexible and Conductive Printed Graphene for Wireless Wearable Communications Applications by Xianjun Huang, Ting Leng, Mengjian Zhu, Xiao Zhang, JiaCing Chen, KuoHsin Chang, Mohammed Aqeeli, Andre K. Geim, Kostya S. Novoselov, & Zhirun Hu. Scientific Reports 5, Article number: 18298 (2015) doi:10.1038/srep18298 Published online: 17 December 2015

This is an open access paper.

The next and final item concerns supercapacitors for wearable tech, which makes it slightly different from the other items and is why, despite the date, this is the final item. The research comes from Case Western Research University (CWRU; US) according to a Dec. 16, 2015 news item on Nanowerk (Note: A link has been removed),

Wearable power sources for wearable electronics are limited by the size of garments.

With that in mind, researchers at Case Western Reserve University have developed flexible wire-shaped microsupercapacitors that can be woven into a jacket, shirt or dress (Energy Storage Materials, “Flexible and wearable wire-shaped microsupercapacitors based on highly aligned titania and carbon nanotubes”).

A Dec. 16, 2015 CWRU news release (on EurekAlert), which originated the news item, provides more detail about a device that would make wearable tech more wearable (after all, you don’t want to recharge your clothes the same way you do your phone and other mobile devices),

By their design or by connecting the capacitors in series or parallel, the devices can be tailored to match the charge storage and delivery needs of electronics donned.

While there’s been progress in development of those electronics–body cameras, smart glasses, sensors that monitor health, activity trackers and more–one challenge remaining is providing less obtrusive and cumbersome power sources.

“The area of clothing is fixed, so to generate the power density needed in a small area, we grew radially-aligned titanium oxide nanotubes on a titanium wire used as the main electrode,” said Liming Dai, the Kent Hale Smith Professor of Macromolecular Science and Engineering. “By increasing the surface area of the electrode, you increase the capacitance.”

Dai and Tao Chen, a postdoctoral fellow in molecular science and engineering at Case Western Reserve, published their research on the microsupercapacitor in the journal Energy Storage Materials this week. The study builds on earlier carbon-based supercapacitors.

A capacitor is cousin to the battery, but offers the advantage of charging and releasing energy much faster.

How it works

In this new supercapacitor, the modified titanium wire is coated with a solid electrolyte made of polyvinyl alcohol and phosphoric acid. The wire is then wrapped with either yarn or a sheet made of aligned carbon nanotubes, which serves as the second electrode. The titanium oxide nanotubes, which are semiconducting, separate the two active portions of the electrodes, preventing a short circuit.

In testing, capacitance–the capability to store charge–increased from 0.57 to 0.9 to 1.04 milliFarads per micrometer as the strands of carbon nanotube yarn were increased from 1 to 2 to 3.

When wrapped with a sheet of carbon nanotubes, which increases the effective area of electrode, the microsupercapactitor stored 1.84 milliFarads per micrometer. Energy density was 0.16 x 10-3 milliwatt-hours per cubic centimeter and power density .01 milliwatt per cubic centimeter.

Whether wrapped with yarn or a sheet, the microsupercapacitor retained at least 80 percent of its capacitance after 1,000 charge-discharge cycles. To match various specific power needs of wearable devices, the wire-shaped capacitors can be connected in series or parallel to raise voltage or current, the researchers say.

When bent up to 180 degrees hundreds of times, the capacitors showed no loss of performance. Those wrapped in sheets showed more mechanical strength.

“They’re very flexible, so they can be integrated into fabric or textile materials,” Dai said. “They can be a wearable, flexible power source for wearable electronics and also for self-powered biosensors or other biomedical devices, particularly for applications inside the body.” [emphasis mine]

Dai ‘s lab is in the process of weaving the wire-like capacitors into fabric and integrating them with a wearable device.

So one day we may be carrying supercapacitors in our bodies? I’m not sure how I feel about that goal. In any event, here’s a link and a citation for the paper,

Flexible and wearable wire-shaped microsupercapacitors based on highly aligned titania and carbon nanotubes by Tao Chen, Liming Dai. Energy Storage Materials Volume 2, January 2016, Pages 21–26 doi:10.1016/j.ensm.2015.11.004

This paper appears to be open access.