Electromagnetic wave absorber enables clear 6G comms

Terahertz waves are predicted to serve as carriers for the upcoming sixth-generation networks, with recent reports on tests with terahertz waves showing data transmission speeds of up to 240 Gbps. But due to their higher frequency and shorter wavelength, terahertz waves are subject to greater interference from electromagnetic noise, making clear and secure transmission a challenge.

That’s where electromagnetic wave absorbers come in: they can inhibit the transmission or reflection of electromagnetic waves and, when placed on the covers of transmitters and antennas, help to enhance communication precision.

Now, researchers at The University of Tokyo and Japanese chemical and iron-based alloy manufacturer Nippon Denko claim in a new study to have developed the world’s thinnest electromagnetic wave absorber, capable of absorbing waves in the 0.1–1 THz range. To date, only absorbers for waves below 0.3 THz have been made commercially available, but a frequency range beyond this is anticipated to be used for large-capacity 5G and 6G.

“This frequency range is expected to be used for various applications including wireless communications, noncontact vital monitoring systems, quality-inspection scanning systems via tomographic imaging, and security sensing for detecting hazardous materials,” said Tokyo’s Professor Shin-ichi Ohkoshi, corresponding author on the study published in ACS Applied Materials & Interfaces.

Composed of an electrically conductive metal oxide called lambda-trititanium-pentoxide (λ-Ti₃O₅), insulated within a titanium dioxide (TiO₂) coating, the absorber is made entirely of titanium and oxygen. The absorber is made in powder form, which can be turned into an ultrathin film through compression moulding and then applied to surfaces as needed.

“Our strategy was to combine an electrically conductive material with an insulating material,” Ohkoshi said. “When a terahertz wave passes through, its alternating electric field induces scattering of the electric current generated inside of the conductive material, which causes energy loss and results in the dissipation of electromagnetic energy. This dissipation of interfering waves enables the suppression of noise, ie, unwanted waves, resulting in a clear signal.”

As the film is only 48 µm thick (an average human hair is around 100 µm) and titanium is a highly abundant element, the absorber is economical for mass production and can be used even inside compact devices. It is also resistant to heat, water, light and organic solvents, and so can be used in outdoor environments and can even withstand harsh conditions.

“The higher frequency range above 0.3 THz remains an unexplored area in materials science and I have been eager to contribute to its development,” Ohkoshi said. “Our next step is to further develop the terahertz absorber and work toward its practical application, so that we can contribute to a more sustainable, eco-friendly, superfast wireless future.”

Image caption: Lambda-trititanium-pentoxide can be synthesised on a large scale relatively easily and cost-effectively, and its surface coating can be obtained simply by mixing it with titanium dioxide nanoparticles. Image ©2025 S Ohkoshi, Y Tsuzuo, M Yoshikiyo et al under CC-BY-ND