To satisfy the requirements of the Defense Advanced Research Projects Agency (DARPA; Arlington, VA) Near Zero Power RF and Sensor Operations (N-ZERO) program with a goal of developing reliable sensors that improve warfighter safety, researchers at Northeastern University (Boston, MA) have developed an infrared (IR) sensor based on a plasmonically enhanced micromechanical photoswitch that does precisely what N-ZERO demands: remain dormant with near-zero power consumption until awakened by an external trigger or stimulus—in this case, a heat source that could be a potential threat.
The new type of photoswitch essentially consists of a light-actuated microelectromechanical (MEM) relay that, through a plasmonically enhanced thermomechanical coupling mechanism, harvests the energy in a specific spectral band of light and uses it to mechanically create a conducting channel between the device terminals only when that specific light is present, enabling near-zero power consumption in the standby mode. The plasmonically enhanced micromechanical photoswitches (PMPs) are sensitive to only a narrow spectral signal, thanks to photolithographically engineered plasmonic nanostructures. When IR radiation matching the absorption band defined by the nanostructures is absorbed and converted to heat, it causes a downward bend in the thermally sensitive bimaterial legs of the device and a vertical displacement of a metal tip that then touches the opposite terminal, creating a conductive channel when the IR power exceeds the designed threshold level. Multiple PMPs can be engineered on the same chip to detect different IR signals such as tailpipe combustion signals, burning wood in a forest fire, or possibly the presence of human heat energy. Reference: Z. Qian et al., Nature Nanotechnol. online, doi:10.1038/nnano.2017.147 (Sep. 11, 2017).
