Fire-Beetle-Inspired Aerogel Absorbs Microwaves Across a Record-Broad Band

A beetle that can smell a forest fire from more than a hundred kilometers away has inspired a new class of ultralight materials that swallow microwaves across an unprecedented range of frequencies. In a study published in Advanced Science, researchers report a bio-inspired aerogel that achieves an effective absorption bandwidth of 9.43 gigahertz within the 2 to 18 GHz band, the widest value reported to date for a carbon-based microwave absorber, while weighing so little that a sample can rest on a flower stamen. The material contains only 3.74 weight percent of active absorber in an epoxy matrix, yet it attenuates incoming electromagnetic waves with a minimum reflection loss of −63.10 dB, meaning that more than 99.999 percent of the incident power is dissipated rather than reflected.

The biological prototype is Melanophila acuminata, the fire-chaser beetle, whose thoracic pit organs house infrared sensilla capable of detecting the thermal glow of distant burning forests. Using scanning electron microscopy, the team mapped the ultrastructure of these natural photodetectors and found a densely packed array of synaptic-like protrusions separated by gaps, each covered in nanoscale wrinkles and dotted with nanopores. The gaps provide paths for repeated reflection and scattering of incoming radiation, the micrometer-scale protrusions act as resonant structures, the nanoscale wrinkles resonate with far-infrared waves, and the nanopores push the impedance of the sensillum closer to that of air, so that radiation enters rather than bounces off. The sensilla detect infrared rather than microwave radiation, but the researchers recognized that the underlying wave-management principles were transferable.

Crucially, the team emphasizes that the strategy is one of functional translation rather than geometric copying. The beetle’s architecture operates in the infrared regime, whereas the synthetic material targets microwaves in the 2 to 18 GHz band. The designers therefore mapped each biological feature onto a corresponding synthetic element: the cavities and interspaces of the sensillum became a three-dimensional porous carbon framework that lowers the effective permittivity and improves impedance matching with free space; the synaptic protrusions became rough, interconnected carbon struts decorated with cerium dioxide and MXene nanosheets; and the nanoscale wrinkles and pores became abundant heterointerfaces, oxygen vacancies, and surface terminations that act as polarization and loss centers. The result is a hierarchical structure that preserves the beetle’s strategy of multiscale impedance regulation and interfacial energy dissipation while rescaling the characteristic dimensions to microwave physics.

Before fabricating anything, the team validated the concept computationally. They modeled the aerogel as an irregular Voronoi polyhedral framework, a geometry chosen both for its resemblance to the biological template and because structural irregularity favors absorption. Density functional theory calculations on the two chosen nanomaterials, cerium dioxide and Ti3C2Tx MXene, revealed strong electronic coupling at their junction. Differential charge density analysis showed electrons accumulating on the cerium dioxide side and depleting on the MXene side, creating a built-in electric field and prominent interfacial dipoles. Work function calculations quantified the driving force: 6.030 eV for the cerium dioxide surface versus 5.394 eV for Ti3C2OF, the stoichiometry derived from quantitative elemental analysis of the actual synthesized MXene. Electrons therefore flow from MXene to cerium dioxide until the Fermi levels align, strengthening Maxwell-Wagner interfacial polarization, a key dielectric loss mechanism under an alternating electromagnetic field.

The electronic structure calculations added further support. The density of states near the Fermi level is dominated by titanium 3d orbitals, indicating that the heterostructure retains good intrinsic conductivity channeled through the MXene layers, which enables energy dissipation via conduction losses. Significant orbital hybridization among Ce 4f, Ti 3d, O 2p, and F 2p states above the Fermi level creates unoccupied hybridized states into which incident radiation can excite electrons, opening an additional channel for energy dissipation. COMSOL electromagnetic simulations of the materialized unit cell, combined with transmission line theory and the ABCD matrix method, predicted reflection loss below −10 dB, corresponding to more than 90 percent absorption, across nearly the entire 2 to 18 GHz range.

To realize the design experimentally, the researchers used melamine foam as a sacrificial template because its skeletal structure and pore dimensions closely mimic the theoretically optimized Voronoi-like architecture. The foam was impregnated with a dispersion of cerium dioxide and MXene nanosheets, freeze-dried, and then heat-treated under argon at 350 and 800 degrees Celsius, which carbonizes the template and burns it away as a sacrificial scaffold. The resulting aerogels have densities between 0.018 and 0.117 grams per cubic centimeter and shrink only 5.60 to 13.07 percent during formation. X-ray diffraction confirmed cubic cerium dioxide and the characteristic (002) reflection of MXene, Raman spectroscopy identified the component phases and the graphitic carbon framework, and X-ray photoelectron spectroscopy revealed the coexistence of Ce3+ and Ce4+ states, a signature of high oxygen-vacancy concentration in the ceria lattice.

Those oxygen vacancies matter enormously for performance. The presence of Ce3+ introduces additional electronic energy levels and local charge imbalance, generating defect dipoles that relax under an alternating electromagnetic field and convert wave energy into heat. The minor titanium dioxide phase detected in the spectra further enhances interfacial polarization at newly formed heterogeneous boundaries. When the aerogels were vacuum-impregnated with epoxy resin for testing, dielectric measurements showed that increasing nanomaterial loading raised the complex permittivity substantially, while the permeability remained essentially unchanged because the primary components are non-magnetic. Cole-Cole analysis revealed four distinct Debye relaxation processes in the optimal samples, and impedance spectroscopy showed low charge-transfer resistance at high frequencies, consistent with the highly conductive MXene and carbon networks.

The absorption measurements validated every element of the design. The CMX5 sample achieved a minimum reflection loss of −63.10 dB at 3.1 mm thickness and 13.58 GHz, with an effective bandwidth of 6.46 GHz, and reached its maximum bandwidth of 7.82 GHz at 4.0 mm thickness. The CMX3 sample performed even more impressively in bandwidth terms: at 3.9 mm it covered 9.43 GHz, spanning 6.70 to 16.13 GHz, surpassing all previously reported carbon-based absorbers while using an ultralow 3.74 weight percent loading. By simply adjusting thickness, the material can be tuned to cover 100 percent of the X-band and up to 84.5 percent of the Ku-band, or 73 percent of the C-band, because polarization relaxation processes dominate at low and mid frequencies. Radar cross-section simulations confirmed that coated objects would be substantially harder for radar to detect.

The team also demonstrated practical relevance beyond the laboratory bench. When a resin patch of the material was placed over a chip inside a communication device, the measured radiation intensity dropped from 110 volts per meter on the bare chip to roughly 10 to 40 volts per meter, a striking reduction in electromagnetic pollution at the component level. The aerogels additionally proved mechanically resilient, retaining elasticity after compression and supporting a 100-gram load with minimal deformation, thermally insulating, with a cubic centimeter sample keeping its top surface below 50 degrees Celsius on a hot plate at 100 to 200 degrees Celsius, and fire-resistant, with the framework remaining largely intact after direct ablation. Filling the aerogel with epoxy even raised the resin’s thermal conductivity and glass transition temperature, because the continuous carbon network provides pathways for phonon transport and mechanically interlocks with the polymer chains.

The broader significance of the work lies in demonstrating that a biological sensory organ tuned to infrared radiation can be rationally translated into a metamaterial for an entirely different part of the electromagnetic spectrum. Rather than copying the beetle’s geometry, the researchers extracted its design logic, hierarchical impedance grading, radiation trapping through multiple scattering, extended propagation pathways, and interfacial energy conversion, and re-implemented it with cerium dioxide nanoparticles, MXene nanosheets, and a porous carbon scaffold. The synergy between dielectric loss in ceria, conductive and interfacial losses in MXene, and defect dipoles from oxygen vacancies produces complementary attenuation mechanisms that no single component could deliver. With broadband coverage, high absorption efficiency, ultralow density, and minimal filler content combined in one material, the beetle-inspired aerogel points toward next-generation electromagnetic interference shielding, stealth coatings, and protection for the ever-denser wireless electronics of modern life.

Subject of Research: Bio-inspired CeO2/MXene hierarchical aerogels for broadband microwave absorption

Article Title: Modified MXene Aerogel With Broadband Microwave Absorption Inspired by Melanophila Acuminata Beetle

Article References: Liu, Z., Xu, D., Liu, Z., Song, H., Zhang, Q., Zhou, J., & Wen, X. (2026). Modified MXene Aerogel With Broadband Microwave Absorption Inspired by Melanophila Acuminata Beetle. Advanced Science, 13(55), Article e76496. https://doi.org/10.1002/advs.76496

Image Credits: AI Generated

DOI: 10.1002/advs.76496

Keywords: MXene, aerogel, biomimetics, Melanophila acuminata, microwave absorption, electromagnetic interference, CeO2, carbon foam, impedance matching, stealth technology, dielectric loss, DFT calculations