Night-vision windshields on automobiles may someday be possible with advanced thermal imaging technology based on flexible, transparent, atomically thin sheets of carbon, researchers say.
Thermal imaging lets people see the invisible infrared rays that objects shed as heat. Thermal imaging devices have helped soldiers, police, firefighters and others see in the dark and in smoky conditions so they can better do their jobs.
At present, many thermal imaging units need cooling systems to filter out background heat to be able to create useful images. However, these cooling systems complicate the design of the devices, increasing their price and bulkiness.
Now researchers have developed a new thermal imaging system based on sheets of graphene, which are each made from a single layer of carbon atoms organized in a honeycomb pattern. Graphene is extraordinarily strong—about 200 times stronger than steel by weight—and extremely electrically conductive.
The center of the device is a square patch of graphene mixed with microscopic silicon devices (MEMS). This square patch serves as the thermal sensor, converting thermal signals into electrical signals.
“Graphene isn’t only great for transistors and nice for reinforcing structural materials, but it’s also one of the best possible materials we know for infrared detection,” stated study co-author Tomás Palacios, an electrical engineer at the Massachusetts Institute of Technology.
Instead of utilizing a cooling system, the researchers isolated the thermal sensor from the remainder of the system. They did this by using strips of graphene to suspend the thermal sensor in the open air, where it could detect incoming heat. These strips also convey electrical signals from the thermal sensor to the rest of the machine.
The scientists discovered that their device could make out the heat signature of a human hand at room temperature without needing cooling fluids, often called refrigerants. The researchers suggest their findings could in the future result in flexible, transparent, low-cost thermal imaging systems.
“The benefit of significantly reducing the price and increasing the performance of infrared imagers is that now you can start introducing these cameras in many new places,” Palacios informed Live Science. “For instance, in the future, we can have infrared detectors built-in 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.”
Although computers nowadays can use regular cameras to recognize gestures, “it takes a lot of computing power to identify where your hands are and how they are moving,” Palacios stated. “By utilizing an infrared sensor, imaging of the body is simplified, since it’s very easy for thermal imaging to identify the contours of the human body with respect to backgrounds, which tend to be at a lower temperature.”
Thin, flexible, clear thermal imaging systems “may be integrated into the windshields of automobiles,” suggested Palacios, “You’ll be able to view night-vision systems in real time with out blocking a driver’s regular view of the street.”
The scientists detailed their findings online Oct. 15 in the journal Nano Letters.