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article imageEssential Science: Graphene makes improved night vision tech

By Tim Sandle     Nov 16, 2015 in Science
Graphene is the "wonder material" of our age, discovered just ten years ago. The scientific properties of the material are varied, from electronics to power systems. A new use applies to improved ways of penetrating the dark.
In a new weekly column called "Essential Science," Editor-at-Large Tim Sandle will look into big scientific breakthroughs and how they'll soon impact the world at large.
Graphene has been used to create fold-away computer screens and heralds a new generation of computer chips, due to its efficient way of conducting electricity (and many other applications covered in-depth on Digital Journal.) A further development with graphene, announced this week, is with creation of a prototype for improved, potentially lower-cost, flexible and transparent night vision technology.
Night vision goggles have been around for several decades, initially only used by the military but now popular with home users. Good night vision equipment is strong in two areas, having both sufficient spectral range (beyond just visible light) and sufficient intensity range (ability to produce an image with only a tiny amount of light.)
Such equipment works in one of two ways: utilizing several parts of the electromagnetic spectrum or through thermal imaging. The former process uses image enhancement technology to collect all the available light (a combination of a photocathode and a photomultiplier.) This includes infrared light, which is not visible to the human eye, and amplifies it so the wearer of the goggles can visualize images that would ordinarily be hidden in the dark. With thermal imaging, this is based on 'hot objects', like humans and other animals emitting a heat pattern that can be clarified through variations of infrared light.
The Sun seen through an infrared filter on a DSLR.
The Sun seen through an infrared filter on a DSLR.
Night vision technology has advanced a long-way in the past decade. However, it remains hampered by performance issues and attempts to seek better performance lead to the downside of device weight increasing.
Moreover the technology is being increasingly used by emergency services, the American Chemical Society notes, including the military, police, and firefighters. The technology is not only useful at night to track people or equipment; it also helps to track objects in smoky conditions. Another application is with building inspection, to identify overheating circuits. An alternative is to enable conservationists to detect animals in safari parks, as shown in the photograph below.
Infrared image of possible albino elephant. Kaeng Krachan National Park  Thailand
Infrared image of possible albino elephant. Kaeng Krachan National Park, Thailand
The Nation, Thailand
The reason many thermal imaging based devices are heavy is because they require cryogenic cooling systems in order to filter out background radiation (termed "noise") so that a good quality image is obtained.
To find a more practical solution, researchers have turned to graphene. Graphene is a one atom thick form of graphite and it has many useful properties relating to strength, flexibility and conductivity (it conducts electricity at room temperature like a superconductor at near-absolute zero.)
Making a superlattice with patterns of hydrogenated graphene is the first step in making the materia...
Making a superlattice with patterns of hydrogenated graphene is the first step in making the material suitable for organic chemistry. The process was developed in the Rice University lab of chemist James Tour.
Tour Lab/Rice University
By integrating graphene with silicon micro-electromechanical systems (termed MEMS), a new generation of night vision devices can be produced. Graphene forms the core of the thermal sensor. According to Controlled Environments magazine, initial trials have shown such a device is sensitive enough to detect a person's heat signature at room temperature. Here the research team scientists discovered the prototype device could detect the heat signature of a human hand at room temperature without needing cooling fluids (refrigerants.)
The most important thing is the devices are lightweight and no longer require cryogenic cooling. The device is also flexible, and the researchers behind the device are confident it can be produced at a low-cost.
The lead researcher, Tomás Palacios, told Scientific American: "The advantage of significantly reducing the cost and increasing the performance of infrared imagers is that now you can start introducing these cameras in many new places."
He added: "For example, in the future, we can have infrared detectors integrated in every cellphone and every laptop. That means that in the future, you can control them just by waving your hand in front of them."
The development was carried out at the Massachusetts Institute of Technology, with the findings reported to the journal Nano Letters. The paper is titled “Graphene-Based Thermopile for Thermal Imaging Applications”, and it is free to access.
In related (and recent) graphene news, researchers have used ultra-thin flakes of graphene to construct a very fast and very accurate stopwatch.
More about Graphene, Night vision, infrared, Electromagnetic spectrum
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