Always-alert zero-power IR sensor has promise for national security, IoT
The sensor, which uses virtually zero stand-by power, was developed as part of DARPA’s Near Zero Power RF and Sensor Operations (N-ZERO) program – a primary goal of which is developing fundamental technologies that open the way to new and more-capable sensor systems relevant to national security. However, the researchers also predict that it could have “a groundbreaking impact on the proliferation of the Internet of Things.”
The infrared (IR) digitizing sensor consists of “plasmonically enhanced micromechanical photoswitches” that selectively harvest electromagnetic energy in design-defined spectral bands of interest. It then uses that energy to create, mechanically, a conducting channel between two electrical contacts without using any additional power.
“What is really interesting about the Northeastern IR sensor technology, is that, unlike conventional sensors, it consumes zero stand-by power when the IR wavelengths to be detected are not present,” says Troy Olsson, manager of the N-ZERO Program in DARPA’s Microsystems Technology Office.
“When those IR wavelengths are present and impinge on the Northeastern team’s IR sensor, the energy from the IR source heats the sensing elements which, in turn, causes physical movement of key sensor components. These motions result in the mechanical closing of otherwise open circuit elements, thereby leading to signals that the target IR signature has been detected.”
The sensor includes a grid of nanoscale patches, the specific dimensions of which limit them to absorbing only particular IR wavelengths. Multiple sensing elements are each tuned to absorb a specific IR wavelength.
“Together, these combine into complex logic circuits capable of analyzing IR spectrums,” says Olsson, “which opens the way for these sensors to not only detect IR energy in the environment but to specify if that energy derives from a fire, vehicle, person, or some other IR source.”
One potential application is identification of gasoline-powered vehicles from their IR emissions. The infrared emission spectra of heated tailpipe gases coming from vehicles such as trucks, cars, or aircraft can act as a signature “fingerprint” specific to a vehicle type.
According to the researchers, prototypes of the zero-power digitizing sensor produced a digitized output bit when exposed to infrared radiation in a specific narrow spectral band with the intensity above a power threshold of only ~500 nW, which, they say, is not achievable with any existing photoswitch technologies.
For more, see “Zero Power Infrared Digitizers Based on Plasmonically-enhanced Micromechanical Photoswitches.”
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