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Graphene Supercharges Concrete, Altering the Construction Industry

Posted By Dexter Johnson, IEEE Spectrum, Tuesday, May 1, 2018

Graphene often gets discussed in gee-whiz applications like post-CMOS electronics, or solar cells  that can provide extremely high electricity-to-light conversion ratios.

However, it is perhaps in the more mundane aspects of our world that graphene is providing an important impact. The perfect example of this is graphene in concrete—a material that has been with us since the ancient Romans. In a feature at the beginning of the year, The Graphene Council reported on how the addition of graphene oxide is providing concrete with greater compressive and tensile strength

Now researchers at the University of Exeter in the UK have developed a technique for adding graphene to concrete that provides such a wide gamut of new and improved properties that some are predicting that it could revolutionize the construction industry. 

In research described in the journal Advanced Functional Materials, the University of Exeter researchers demonstrated that the addition of graphene to concrete could improve the material’s compressive strength by 149 percent. This compressive strength increase was accompanied with a 79 per cent increase in flexural strength, a 400 per cent decrease in water permeability, and improved electrical and thermal performance.

The key to this development is that it is completely compatible with today’s large-scale production of concrete. It simply involves suspending atomically thin graphene in water. The resulting process keeps costs low and results in very few defects in the end product

“This ground-breaking research is important as it can be applied to large-scale manufacturing and construction,” said Dimitar Dimov, a PhD student at the University of Exeter and the lead author of the research. “The industry has to be modernized by incorporating not only off-site manufacturing, but innovative new materials as well.”

What may grab the headlines beyond its improved properties is that the graphene-enabled concreted appeals to so-called green manufacturing.

“By including graphene we can reduce the amount of materials required to make concrete by around 50 per cent — leading to a significant reduction of 446 kilograms per ton of the carbon emissions,” said Monica Craciun, professor at Exeter and co-author of the research. “This unprecedented range of functionalities and properties uncovered are an important step in encouraging a more sustainable, environmentally-friendly construction industry worldwide.”

Tags:  CMOS  Concrete  construction  solar cells 

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Graphene-based Image Sensors Offer New Commerical Avenues

Posted By Dexter Johnson, IEEE Spectrum, Tuesday, March 13, 2018

The Mobile World Congress (MWC) held annually in Barcelona, Spain is one of the largest technology conferences in the world. For the last three years, the MWC has been hosting the Graphene Pavilion that showcases the research institutes and technologies that they have developed under the EU’s Graphene Flagship

The Graphene Council visited the Graphene Pavilion last month in Barcelona and we came back with some videos. One of the anchor institutions at the Pavilion is The Institute of Photonics (ICFO)  located just outside of Barcelona. The Graphene Council has been speaking to Frank Koppens at ICFO since 2015 about how graphene was impacting photonics and optoelectronics. 

In our latest visit with them at MWC this year, we got an update on some of the ways they are applying their technologies to various technologies.

In the one shown in the video below, the researchers have developed ultraviolet (UV) sensors for protecting the wearers from overexposure to the sun.

While specifics of the underlying technology are not discussed in the video, it would appear to be based on the CMOS-based image sensor for UV-visible-infrared light that the ICFO developed based on a combination of graphene and quantum dots.

What the ICFO discovered six years ago was that while graphene generates an electron-hole pair for every single photon the material absorbs generates, it doesn’t really absorb that much light. To overcome this limitation of graphene, they combined it with quantum dots with the hybrid material being capable of absorbing 25 percent of the light falling on it. When you combine this new absorption capability with graphene’s ability to make every photon into an electron-hole pair, the potential for generating current became significant.

The ICFO has been proposing applications like this for this underlying technology for years, and producing working prototypes. At the MWC in 2016, the ICFO was exhibiting a heart rate monitor. In that device, when a finger is placed on the photodetector, the digit acts as an optical modulator, changing the amount of light hitting the photodetector as your heart beats and sends blood through your fingertip. This change in signal is what generates a pulse rate on the screen of the mobile device.

This same basic technology is at the heart of another technology ICFO was exhibiting this year (see video below) in which the graphene-based photodector can determine what kind of milk you are about to drink. This could conceivably be used by someone who has a lactose intolerance that could threaten their lives and by using the detector could determine if it was cow’s milk or soy milk, for instance.

While ICFO goes so far as to discuss prices for the devices, it’s not clear that ICFO is really committed to any of these technologies for its wide-spectrum CMOS graphene image sensor, or not. In the case of the heart monitor, the researchers claimed at the time it was really just intended to demonstrate the capabilities of the technology.

The long-range aim of the technology is to improve the design of these graphene-based image sensors to operate at a higher resolution and in a broader wavelength range. Once the camera is improved, the ICFO expects that will be used inside a smartphone or smart watch. In the meantime, these wearable technologies offer intriguing possibilities and maybe even a real commercial avenue for the technology.

Tags:  CMOS  graphene  ICFO  infrared  Mobile World Congress  photodetectors  quantum dots  ultraviolet 

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Graphene and CMOS Become One, Offering New Hope in Electronics

Posted By Dexter Johnson, IEEE Spectrum, Friday, June 9, 2017

 

 

Complimentary metal-oxide semiconductors (CMOS) have served as the backbone of the electronics industry for over four decades.  However, the last decade has been marked by increasing concerns that CMOS will not be able to continue to meet the demands of Moore’s Law in which the number of transistors in a dense integrated circuit doubles approximately every two years. If CMOS is going to continue to be a force in electronics, it will become necessary to integrate CMOS with other semiconductor materials other than silicon.

It appears that research out of The Institute of Photonic Sciences in Barcelona (ICFO) and supported by The Graphene Flagship has found a way to integrate graphene into a CMOS integrated circuit

In research described in the journal Nature Photonics, the ICFO researchers combined the graphene-CMOS device with quantum dots to create an array of photodetectors.

While the photodetector arrays could enable digital cameras capable of seeing UV, visible and infrared light simultaneously, the technology could have a wide range of applications, including microelectronics to low-power photonics.

“The development of this monolithic CMOS-based image sensor represents a milestone for low-cost, high-resolution broadband and hyperspectral imaging systems" said, Frank Koppens, a professor at ICFO in a press release.

Koppens, who The Graphene Council interviewed back in 2015believes that "in general, graphene-CMOS technology will enable a vast amount of applications, that range from safety, security, low cost pocket and smartphone cameras, fire control systems, passive night vision and night surveillance cameras, automotive sensor systems, medical imaging applications, food and pharmaceutical inspection to environmental monitoring, to name a few."

The researchers were able to integrate the graphene and quantum dots into a CMOS chip by first depositing the graphene on the CMOS chip. Then this graphene layer is patterned to define the pixel shape. Finally a layer of quantum dots is added.

“No complex material processing or growth processes were required to achieve this graphene-quantum dot CMOS image sensor,” said Stijn Goossens, another researcher from ICFO in Barcelona. “It proved easy and cheap to fabricate at room temperature and under ambient conditions, which signifies a considerable decrease in production costs. Even more, because of its properties, it can be easily integrated on flexible substrates as well as CMOS-type integrated circuits."

The graphene-enabled CMOS chip achieves its photoresponse through something called the photogating effect, which starts as the quantum dot layer absorbs light and transfers it as photo-generated holes or electrons to the graphene. These holes or electrons move through the material because of a bias voltage applied between two pixel contacts. The photo signal triggers a change in the conductivity of the graphene and it is this change that is sensed. Because graphene has such high conductivity, a small change can be quickly detected giving the device extraordinary sensitivity.

Andrea Ferrari, science and Technology offficer of the Graphene Flagship added: "The integration of graphene with CMOS technology is a cornerstone for the future implementation of graphene in consumer electronics. This work is a key first step, clearly demonstrating the feasibility of this approach.”

Tags:  CMOS  digital cameras  graphene  low-power photonics  quantum dots  The Graphene Flagship 

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