Graphene Night-Vision Contact Lenses
by Francie Diep / 03.18.2014
“Nobody has made night-vision contact lenses yet… but there’s a glimpse at how that technology might work, if it ever comes to be. University researchers have created a super-light, super-thin material that detects infrared light. Infrared includes the wavelengths of light that, in part, help night-vision goggles see warmer objects in the dark. In the future, a material like this could fit into a number of interesting devices. “It can be stacked on a contact lens or integrated with a cell phone,” lead researcher Zhaohui Zhong said in a statement. For now, Zhong and his team’s accomplishment is getting graphene to emit a stronger signal after absorbing infrared light. Graphene—a material composed of a single layer of carbon atoms—is able to absorb a wide spectrum of wavelengths of light, including infrared. Normally, however, graphene absorbs very little of what hits it, producing a weak signal as a result. For any kind of graphene optical device to work, it has to get a strong signal from its graphene detector. Zhong and a team of three other engineers at the University of Michigan constructed a material consisting of two layers of graphene separated by an insulating layer. That material reacted more strongly to infrared light, producing an electrical field that the team measured to deduce how much infrared was hitting it. The material worked at room temperature, which is another accomplishment because previous attempts to amp up graphene’s light detection required the graphene to be cooled to far below freezing. It also worked for a wide range of infrared wavelengths. Infrared detectors in use now are narrower in range, with different materials specializing in detecting near-infrared and mid-infrared wavelengths. Zhong and his team published their work in the journal Nature Nanotechnology.”
NIGHT VISION CONTACT LENSES
Thermal vision: Graphene light detector first to span infrared spectrum
by Kate McAlpine / Mar 16, 2014
“The first room-temperature light detector that can sense the full infrared spectrum has the potential to put heat vision technology into a contact lens. Unlike comparable mid- and far-infrared detectors currently on the market, the detector developed by University of Michigan engineering researchers doesn’t need bulky cooling equipment to work. “We can make the entire design super-thin,” said Zhaohui Zhong, assistant professor of electrical and computer engineering. “It can be stacked on a contact lens or integrated with a cell phone.” Infrared light starts at wavelengths just longer than those of visible red light and stretches to wavelengths up to a millimeter long. Infrared vision may be best known for spotting people and animals in the dark and heat leaks in houses, but it can also help doctors monitor blood flow, identify chemicals in the environment and allow art historians to see Paul Gauguin’s sketches under layers of paint. Unlike the visible spectrum, which conventional cameras capture with a single chip, infrared imaging requires a combination of technologies to see near-, mid- and far-infrared radiation all at once. Still more challenging, the mid-infrared and far-infrared sensors typically need to be at very cold temperatures.
Graphene, a single layer of carbon atoms, could sense the whole infrared spectrum—plus visible and ultraviolet light. But until now, it hasn’t been viable for infrared detection because it can’t capture enough light to generate a detectable electrical signal. With one-atom thickness, it only absorbs about 2.3 percent of the light that hits it. If the light can’t produce an electrical signal, graphene can’t be used as a sensor. “The challenge for the current generation of graphene-based detectors is that their sensitivity is typically very poor,” Zhong said. “It’s a hundred to a thousand times lower than what a commercial device would require.” To overcome that hurdle, Zhong and Ted Norris, the Gerard A. Mourou Professor of Electrical Engineering and Computer Science, worked with graduate students to design a new way of generating the electrical signal. Rather than trying to directly measure the electrons that are freed when light hits the graphene, they amplified the signal by looking instead at how the light-induced electrical charges in the graphene affect a nearby current. “Our work pioneered a new way to detect light,” Zhong said. “We envision that people will be able to adopt this same mechanism in other material and device platforms.”
To make the device, they put an insulating barrier layer between two graphene sheets. The bottom layer had a current running through it. When light hit the top layer, it freed electrons, creating positively charged holes. Then, the electrons used a quantum mechanical trick to slip through the barrier and into the bottom layer of graphene. The positively charged holes, left behind in the top layer, produced an electric field that affected the flow of electricity through the bottom layer. By measuring the change in current, the team could deduce the brightness of the light hitting the graphene. The new approach allowed the sensitivity of a room-temperature graphene device to compete with that of cooled mid-infrared detectors for the first time. The device is already smaller than a pinky nail and is easily scaled down. Zhong suggests arrays of them as infrared cameras. “If we integrate it with a contact lens or other wearable electronics, it expands your vision,” Zhong said. “It provides you another way of interacting with your environment.” While full-spectrum infrared detection is likely to find application in military and scientific technologies, the question for the general tech market may soon be, “Do we want to see in infrared?” The device is described in a paper titled “Graphene photodetectors with ultra-broadband and high responsivity at room temperature,” which appears online in Nature Nanotechnology.”
“The corona discharge seen here is off a corona ring of a 500-kV high-tension line, which is mean to limit corona discharges. But they don’t eliminate all of them.”
Animals see power lines as glowing, flashing bands, research reveals
by Damian Carrington / 12 March 2014
“Power lines are seen as glowing and flashing bands across the sky by many animals, research has revealed. The work suggests that the pylons and wires that stretch across many landscapes are having a worldwide impact on wildlife. Scientists knew many creatures avoid power lines but the reason why was mysterious as they are not impassable physical barriers. Now, a new understanding of just how many species can see the ultraviolet light – which is invisible to humans – has revealed the major visual impact of the power lines. “It was a big surprise but we now think the majority of animals can see UV light,” said Professor Glen Jeffery, a vision expert at University College London. “There is no reason why this phenomenon is not occuring around the world.” Dr Nicolas Tyler, an ecologist at UIT The Arctic University of Norway and another member of the research team, said: “The flashes occur at random in time and space, so the power lines are not grey and passive, but seen as lines of light flashing.” He said the discovery has global significance: “The loss and fragmentation of habitat by infrastructure is the principle global threat to biodiversity – it is absolutely major. Roads have always got particular attention but this will push power lines right up the list of offenders.” The avoidance of power lines can interfere with migration routes, breeding grounds and grazing for both animals and birds.
“UV camera inspection of power lines reveals coronal discharges, but would appear much brighter to animals who see the full UV spectrum.”
Autopsies on dozens of mammals from zoos and abbatoirs showed their eyes were able to see UV, including cattle, cats, dogs, rats, bats, okapi, red pandas and hedgehogs. Also on the list were reindeer and further work published in the journal Conservation Biology showed these animals, whose eyes are specially adapted to the dark Arctic winters, are particularly sensitive to UV light. UV vision helps reindeer find plants in snow cover, but in the depths of winter their wide irises and sensitive eyes means the power lines appear particularly bright. The avoidance of power lines had been explained in the past by the corridors cut through forests to accommodate them, where animals would be exposed in the open to predators. But this explanation could not apply in the treeless tundra of northern Norway, where 220,000 reindeer are tended by 7,000 herders from the traditional Sami people. “Right now, there is a plan to build a 186-mile long power line in north Norway,” said Tyler. “This new work will encourage power companies to negotiate with herders about where they put the power lines.” Around the world, Tyler said: “There are hundred of examples of animals avoiding power lines. Now we know that, not only do these clear-cut corridors mean exposure to predators, at the same time there is this damn thing flashing at you.”
“UV vision help reindeers find plants in snow cover, but in the depths of winter their wide irises and sensitive eyes means the power lines appear particularly bright.”
Jeffery said burying all power cables would be unrealistically expensive but added that one idea would be to put a non-conducting shield around the cable to screen it from view. The UV light, which is caused by electricity ionising the air around cables, are a major source of inefficiency for electricity companies and also cause the hissing or crackling noises sometimes heard. Power companies already use helicopter-mounted UV cameras to monitor power cables, because the flashes can be an early sign of conduction problems, but the cameras only record a very narrow range of UV. “Animals see across the range, so the intensity of light seen by them is much more than seen by the helicopter flights,” said Jeffery.”
HIGH VOLTAGE IMAGING
High Voltage Image Making, Exploring the Use of Electrical Discharge to Create Photographs
by Rollin Bishop / March 20, 2014
“High Voltage Image Making is a photography project by artist Phillip Stearns that explores the use of electrical discharge in creating interesting images. In a process developed over the last year, Stearns uses around 15,000 volts to create interesting images using instant film. The project has an ongoing Kickstarter crowdfunding campaign.”
the NAKED EYE
Invisible: How to see beyond sight
by Michael Brooks / 20 March 2014
“The naked eye is not a reliable guide to the world. If you believed your eyes, you might conclude that the head louse is pretty much the smallest thing in existence. Fortunately, we can overcome this sensory limitation. The invention of the microscope, for example, allowed Robert Hooke and others to document hitherto unseen aspects of nature – details of the flea and other disease-bearing parasites, and of course the existence of microbes such as bacteria. Without that knowledge, we wouldn’t be living as long as we do. If we had stuck with our natural vision alone, we would also have very little conception of what is going on at the other end of the size scale. The invention of the telescope changed our view of the universe. And eventually, we learned to use spectrographs to split light into its component parts and so reveal the chemical composition of stars and distant planetary atmospheres. And yet, for all our technological sophistication, there is still more invisible stuff to uncover. Dark matter and dark energy together make up 95 per cent of the universe. Neither shines in the conventional way, so we have had to be ingenious to discern what our eyes cannot see.
That’s how dark matter came to light in the first place: Swiss astronomer Fritz Zwicky was watching galaxy clusters in the 1930s and realised that their motion could only be accounted for by the gravitational pull of invisible mass. Today, we suspect dark matter is made of particles that could be detected by a series of ever more sensitive experiments. The front runner is LUX, a vast vat of xenon atoms wired to equipment to detect the energy released by a collision between a dark matter particle and a xenon nucleus. Its trial run last October turned up nothing, but the researchers are undaunted. “Finding the Higgs boson took almost 50 years,” says LUX team member Henrique Araujo of Imperial College London. Dark energy remains another unseen, inexplicable component of the universe. The latest instrument on the case is the Dark Energy Survey, which will analyse light from over 300 million galaxies to try to uncover what dark energy really is. Our assault on the invisible universe also involves observing how galaxy clusters evolve, as well as looking at how structures in the cosmic microwave background radiation have changed in the last 13 billion years and how light’s path warps as it travels across the heavens. With that multi-pronged approach, we should avoid being fooled by a distortion in any one of our cosmic microscopes. Josh Frieman, director of the Dark Energy Survey sees great progress in the coming years. “As Abe Lincoln might have said, you can perhaps fool one dark energy probe, but not all of them,” he says. Our technology for shedding light on hidden realities has come a long way since Robert Hooke’s efforts in the 17th century. Today, a scanning transmission electron holography microscope, for instance, allows us to see down to a resolution of 35 trillionths of a metre. Meanwhile the Large Hadron Collider allows us to probe things that don’t even have a physical presence in the everyday world. Eventually the dark energy and dark matter searches should complete the picture, bringing the invisible essence of the universe within our sights.”
Infrared film turns a war zone into a pink fantasy landscape
by Lauren Davis / 10/06/13
“Many photographers play with the way infrared photography transforms mundane landscapes into cotton candy fantasy lands. The Richard Mosse-directed video installationThe Enclave goes a step further, juxtaposing those landscapes against the lives of rebel groups in the Democratic Republic of Congo.
In the video above, Mosse discusses the project, and we get to see some of the sequences from The Enclave. He, along with cinematographer Trevor Tweeten and sound designerBen Frost, infiltrated armed rebel groups in the eastern Democratic Republic of Congo to capture them on film. He used discontinued military surveillance film that registers infrared light that was original meant to spot camouflaged people and objects, rendering the invisible visible. And by showing video of these people and these areas to Western audiences, Mosse feels he is doing just that, making visible what is so often invisible. He also means to make his war photography beautiful as a way to make people pay attention to it. The oddly colored landscapes attract the eye, enticing the viewer to sit and watch the people who pop out against the backgrounds. It also, he believes, creates an ethical problem in the viewers’ minds, as they find themselves finding these depictions of human suffering as aesthetically beautiful. The Enclave is shown on as an installation, projected on six screens simultaneously. It is currently showing at the Venice Biennale in the Pavilion of Ireland, where it will be until November 24th. The videos below give you an idea of what the installation looks like:
Mosse also has still infrared images from the project up at his website.”