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Researchers in China report a surprising new route to radar stealth: a thin, carbonized coating derived from a common plant. Combining ancient biology with modern nanomaterials, the team says the film can soak up almost all Ku‑band radar waves and could dramatically reduce an aircraft's radar cross section.
From loofah to low observable material
Scientists from Chinese research institutions and the China Aerospace Science and Industry Corporation (CASIC) converted dried loofah — a fibrous plant long used as a bath sponge — into a lightweight carbon scaffold. They then decorated that structure with nickel–cobalt oxide (NiCo2O4) magnetic nanoparticles to produce a composite called NCO-2. The resulting film is just 4 mm thick but, according to the study published in High Power Laser and Particle Beams, can absorb more than 99.99% of incident electromagnetic energy in the Ku band (12–18 GHz).
Why the structure matters
The key lies in the plant's natural three-dimensional network of cellulose fibers. After carbonization, this network becomes a conductive, ultralight scaffold — a "microforest" of interconnected channels. Electromagnetic waves entering the material undergo multiple internal reflections along tortuous paths, increasing the interaction length and enhancing energy loss to the material.
Electromagnetic-to-thermal conversion
- Multiple reflections lengthen the wave's path through the absorber.
- The NiCo2O4 nanoparticles provide magnetic loss mechanisms that dissipate energy.
- The conductive carbon framework enables free-electron motion and Joule heating, turning incoming radar energy into heat.
Together these effects give the thin film exceptional absorption even for radar pulses coming from directly above — a critical test for satellite-based Ku‑band sensors.
Performance, implications and numbers
Study authors claim that applying this coating could shrink the radar cross section (RCS) of a stealth aircraft dramatically. As an example, an object with a vertical RCS of 50 square meters might be reduced to under 1 square meter, making detection by satellite radars far more difficult. RCS is a standardized way to express how "large" an object appears to radar; reducing it by orders of magnitude is the core goal of stealth engineering.
Sustainable materials and future prospects
Beyond the military angle, the research highlights a broader trend: developing high-performance carbon materials from bio-based, sustainable precursors. Converting agricultural or plant waste into advanced functional materials could lower cost and environmental footprint compared with purely synthetic routes. The authors also note everyday analogues — the same loofah-like material has traditional uses as bath sponges — underscoring how ancient natural structures can inspire modern technology.
Questions remain about scalability, environmental resistance, durability under flight conditions, and detection across other radar bands. Still, this work offers a provocative demonstration of how simple biological architectures, combined with targeted nanochemistry, can produce powerful electromagnetic-absorbing coatings.
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