Pixel-level metal blackbody microcavities via hierarchical laser writing

This study presents a new method for creating black coated metal surfaces with ultra-high emissivity using the method of hierarchical femtosecond laser writing. Researchers created pixel-level blackbody microcavities with microscale periodic pores by engraving microscale periodic pores. This allowed an emissivity over a wide spectral range, from visible light to long-wave infrared (0.25–20 μm). Unlike traditional bulky blackbody surfaces, these super-thin structures exhibit broadband absorption and can function as super black material surfaces without additional coatings.

The darkest black surfaces created through this technique demonstrate an average emissivity exceeding 0.94. They also exhibit ultralow reflectivity below 0.004 across infrared wavelengths, rivalling and, moreover, outperforming commercial IR coatings like Acktar Metal Velvet. The laser-designed structures significantly enhance stray light suppression. They achieve strong light trapping through integrating rough surface scattering, plasmonic effects, and geometrical optics.

The researchers programmed local emissivity variations by adjusting the depth and diameter of the microcavities. This advancement has progressed applications like thermal IR encryption, high-resolution grayscale infrared imaging, and digital thermal displays. Furthermore, the black coating retained its performance when exposed to extreme temperatures of up to 500°C by showcasing its exceptional thermal stability in harsh conditions.

The new microcavities performed comparably to the hemispherical emissivity of Acktar’s Metal Velvet coating. Those demonstrated an enhanced angular performance by maintaining emissivity even at incidence angles reaching 70 degrees and exhibited their ability to create detailed IR images without visible surface modifications. All of these highlighted the potential for stray light suppression in advanced optical systems, thermal management, and secure IR communications.

To sum up, this work paves the way for compact, durable, and high-performance ultra black surfaces, offering a breakthrough in designing black coated materials for next-generation optical, imaging, and IR technologies.

Chong-Kuong Ng et al. ,Pixel-level metal blackbody microcavities via hierarchical laser writing.Sci. Adv.11,eadu0608(2025).DOI:10.1126/sciadv.adu0608