A Tunable Metasurface Filter Could Give Future Drones Smart Infrared Crop-Monitoring Powers

Researchers from the City University of New York, the University of Rochester, the University of Melbourne, and RMIT University have developed a compact sensor built around image-processing metasurfaces and which could be fitted to drones to deliver cost-effective large-scale crop monitoring for irrigation, fertilization, and pest control.

"While a few recent demonstrations have achieved analog edge detection using metasurfaces, most of the devices demonstrated so far are static," explains co-first and co-corresponding author Michele Cotrufo of the team's creation. "Their functionality is fixed in time and cannot be dynamically altered or controlled. "Yet, the ability to dynamically reconfigure processing operations is key for metasurfaces to be able to compete with digital image processing systems. This is what we have developed."

The team's work is based on a vanadium dioxide filter system, capable of switching between delivering infrared edge detection and full-detail imaging on demand. "Materials such as vanadium dioxide add a fantastic tuning capability to render devices 'smart,'" Madhu Bhaskaran, co-author on the paper, explains. "When the temperature of the filter is changed, the vanadium dioxide transforms from an insulating state to a metallic one, which is how the processed image shifts from a filtered outline to an unfiltered infrared image."

The idea behind the metasurface filter: delivering a flat-optic sensor that could be fitted to drones and satellites, delivering the sort of smart imaging capabilities that would normally take a power-hungry digital system and heavy lenses in a much more compact package. These sensors could then be used for large-scale crop monitoring, warning when areas are in need to changes to irrigation, fertilization, or are suffering an attack from pests.

The filter system is, the team claims, able to be mass-manufactured at temperatures compatible with existing manufacturing techniques — with co-author Shaban Sulejman suggesting it could "move from research to real-world use rapidly." RMIT University, meanwhile, has a vested interest in its success: the organization holds a US patent and has a pending Australian patent on its method of producing the vanadium dioxide film used in the project.

The team's work has been published in the journal Nature Communications under open-access terms.