University of Michigan engineering researchers have developed infrared technology that 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% of the light that hits it. If the light can’t produce an electrical signal, graphene can’t be used as a sensor.
