New technique to print 3D materials with optical or microwave properties developed

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Moth eye-inspired omnidirectional microwave antenna. Image: Hojat Rezaei Nejad, Tufts University, Nano Lab
Image:

Moth eye-inspired omnidirectional microwave antenna. Image: Hojat Rezaei Nejad, Tufts University, Nano Lab

Metamaterials can be designed and printed to demonstrate unique electromagnetic properties not found in nature

Researchers from Tufts University's Nano Lab claim to have devised a novel hybrid fabrication technique enabling the 3D printing of  metamaterials with unique optical or microwave properties.

According to the researchers, the method uses different techniques - 3D printing, etching and metal coating - to create metamaterials characterised by complex geometries and unique functionalities for wavelengths in the microwave range.

Metamaterials are artificially engineered materials that can be designed to demonstrate unique electromagnetic properties not found in nature. Such materials may find their use in a variety of applications such as sensors, phase shifters, absorbers, and modulators.

In the current study, the researchers used stereolithography (SLG) technique for 3D printing of metamaterials. In SLG, light is focused to polymerise photo-curable resins into the preferred shapes.

The team then created a variety of new optical devices, which they describe as metamaterial embedded geometrical optics (MEGO) devices. These included a frequency selective moth eye hemispherical absorber, curved wide-angle metamaterial absorbers/reflectors and mushroom-type metamaterials.

The frequency selective hemispherical absorber is an omnidirectional microwave antenna inspired by the moth's compound eye. The main feature of the device is its ability to absorb electromagnetic signals coming from any direction at specific wavelengths.

The mushroom-type metamaterials device is basically an array of small mushroom shaped structures, where each structure holds a tiny patterned metal resonator.

In this device, the geometry and the spacing of the "mushrooms" can be changed to allow absorption of microwaves of certain frequencies.

The team also developed parabolic reflectors capable of absorbing and transmitting specific frequencies.

The functionality and performance of all these devices were validated through simulation and measurement using terahertz continuous-wave spectrometer.

Researchers believe MEGO devices can reach terahertz and optical frequencies in the near future with further improvements in 3D printing resolutions.

They also suggest that these 3D printed metamaterials could be used to design telecommunication antennas, imaging detectors and sensors for medical diagnosis.

The findings of the study are published in the journal Microsystems & Nanoengineering.

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