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Researchers have devised a method for using an origami-based structure to create radio frequency filters that have adjustable dimensions.

The method would enable devices to change which signals they block throughout a large range of frequencies, researchers say.

The new approach to creating these tunable filters could have a variety of uses, including antenna systems capable of adapting to ambient conditions in real-time and the next generation of electromagnetic cloaking systems that could be reconfigured on the fly to reflect or absorb different frequencies.

The team focused on one particular pattern of origami, called Miura-Ori, which has the ability to expand and contract like an accordion.

Folded filter

“The Miura-Ori pattern has an infinite number of possible positions along its range of extension from fully compressed to fully expanded,” says Glaucio Paulino, the chair of engineering and a professor in the Georgia Tech School of Civil and Environmental Engineering. “A spatial filter made in this fashion can achieve similar versatility, changing which frequency it blocks as the filter is compressed or expanded.”

The researchers used a special printer that scored paper to allow a sheet to be folded in the origami pattern. An inkjet-type printer was then used to apply lines of silver ink across those perforations, forming the dipole elements that gave the object its radio frequency filtering ability.

“The dipoles were placed along the fold lines so that when the origami was compressed, the dipoles bend and become closer together, which causes their resonant frequency to shift higher along the spectrum,” says Manos Tentzeris, a professor in flexible electronics in the School of Electrical and Computer Engineering at Georgia Tech.

To prevent the dipoles from breaking along the fold line, the perforations were suspended at the location of each silver element and then continued on the other side. Additionally, along each of the dipoles, a separate cut was made to form a “bridge” that allowed the silver to bend more gradually. For testing various positions of the filter, the team used 3D-printed frames to hold it in place.

The origami advantage

The researchers found that a single-layer Miura-Ori-shaped filter blocked a narrow band of frequencies while multiple layers of the filters stacked could achieve a wider band of blocked frequencies.

Because the Miura-Ori formation is flat when fully extended and quite compact when fully compressed, antenna systems that need to stay in compact spaces until deployed, such as those used in space applications, could use the structures. Additionally, the single plane along which the objects expand could provide advantages, such as using less energy, over antenna systems that require multiple physical steps to deploy.

“A device based on Miura-Ori could both deploy and be re-tuned to a broad range of frequencies as compared to traditional frequency selective surfaces, which typically use electronic components to adjust the frequency rather than a physical change,” says Abdullah Nauroze, a graduate student who worked on the project. “Such devices could be good candidates to be used as reflectarrays for the next generation of cubesats or other space communications devices.”

There were also physical advantages to using origami.

“The Miura-Ori pattern exhibits remarkable mechanical properties, despite being assembled from sheets barely thicker than a tenth of a millimeter,” says Larissa Novelino, a graduate student who worked on the project. “Those properties could make lightweight yet strong structures that could be easily transported.”

Results from the study appear in the Proceedings of the National Academy of Science.

The National Science Foundation, the US Department of Defense, the Semiconductor Research Corporation, and the Air Force Office of Scientific Research funded the research. The Brazilian National Council for Scientific and Technological Development also supported the work. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of these agencies.

Source: Georgia Tech