Supreme-black levels enabled by touchproof microcavity surface texture on anti-backscatter matrix

Engineering flexible superblack materials

Flexible superblack materials are crucial for minimizing stray light, complicating object identification, and serving as low reflectance standards. However, the applications of existing superblack materials are limited due to challenges related to cost-effective scalable manufacturing, surface durability, and material conformability. Furthermore, existing fabrication platforms struggle to tailor superblack materials to application-specific needs. This work introduces an engineering platform that combines silicon mold fabrication and polymer casting to produce flexible superblack materials. This platform achieves repeatable wafer-scale production of superblack materials with a minimum reflectance of 0.15% and less than 0.4% across the visible spectrum. The sample reflectance is weakly dependent on illumination angles from 0° to 50° and observer angles from 0° to 70° when the illumination angle is less than 20°. This Lambertian-like reflectance profile enables the material to effectively conceal three-dimensional features in digital images even under intense lighting conditions. This platform can engineer the material surface to withstand tweezer scratches without significantly compromising its reflectance properties. This work introduces an engineering platform for designing flexible superblack materials, addressing key challenges in scalability, surface durability, mechanical flexibility, and customization.

In situ construction of multifunctional femtosecond laser-induced graphene on arbitrary substrates

The construction of laser-induced graphene (LIG) on various substrates is important for expanding new applications. However, current LIG transfer technologies are hampered by limited substrates, complicated processes, induced graphene defects, and single function. Herein, a facile laser processing method is proposed for in situ construction of multifunctional femtosecond laser-induced graphene (FsLIG) on arbitrary substrates utilizing femtosecond laser acting on polyimide tape. Unlike previous LIG transfer research, the proposed method is applicable to any substrates without introducing additional graphene defects, while also exhibiting multifunctionality. Raman spectra results confirm successful fabrication of FsLIG on various substrates involving paper, aluminum, ceramic, and silicon. Taking paper for example, FsLIG demonstrates multifunctional characteristics including high water contact angle (∼153.4°), large absorptance (∼98.8%), low sheet resistance (∼82.0 Ω sq-1), and reliable temperature sensing (∼-0.089% °C-1) properties. Our study provides a reliable pathway for fabricating multifunctional FsLIG on arbitrary substrates.

Lateral flow immunoassay using plasmonic scattering

The lateral flow immunoassay (LFIA) is one of the most successful sensing platforms for real-world point-of-care (POC) testing. However, achieving PCR-level sensitivity without compromising the inherent advantages of LFIA, such as rapid and robust operation, affordability, and naked-eye detection, has remained a primary challenge. In this study, a plasmonic scattering-utilising LFIA was proposed, created by transparentising a nitrocellulose membrane and placing a light-absorbing backing card under the membrane. This LFIA minimised the background signal from its matrix, leading to substantially enhanced sensitivity and enabling naked-eye detection of the plasmonic scattering signal from gold nanoparticles without optics. Our plasmonic scattering-utilising LFIA showed an approximately 2600-4400 times higher detection limit compared with that of commercial LFIAs in influenza A assays. In addition, it exhibited 90% sensitivity in clinical validation, approaching PCR-level sensitivity, while commercial LFIAs showed 23-30% sensitivity. The plasmonic scattering-utilising LFIA plays a ground-breaking role in POC diagnostics and significantly boosts follow-up research.

Suspending Light-Absorbing Nanoparticles in Silica Aerogel Enables Numerous Superblacks

Current strategies for constructing sparse nanostructures for fabricating superblacks are only suitable for a few light-absorbing materials, severely limiting their applications. Herein, ultra-low reflective silica aerogels with ultra-high light transparency are used as solid smokes to individually or simultaneously suspend at least 100 species of light-absorbing nanoparticles with a volume fraction as low as 0.005%, for creating > 100 superblacks in practice and one billion superblacks in theory if taken permutation and combination among these 0D, 1D, or 2D nanoparticles into account. Depending on the composition of suspended nanoparticles and the structure of solid smoke, the resulting mechanically robust superblacks with supplementary properties including magnetism, full-spectrum absorption, high thermal stability, and excellent mechanical strength, are first observed. The wide choice of metallic or semiconductive LNs allows as-made superblacks to glitter in different catalytic reactions, and the resulting superblacks have been on-demand modified for endowing the self-cleaning performance in some contaminable environments. Benefiting from the superblack feature and porous network, these superblack monoliths have shown high-efficiency solar-heat conversion in some emerging light harvesting and managing fields. This powerful synthetic strategy for superblacks is expected to inspire researchers to conduct in-depth investigations on super-black optics, functional materials, etc.

Ultrablack surface with omnidirectional high absorption

Black surface plays an important role in solar-thermal conversion systems and space optical systems. Despite the significant efforts in developing a black surface with strong broadband absorption, realizing scalable omnidirectional high absorption ultrablack surfaces remains challenging. Here, we report an ultrablack surface based on a structural black paint (SBP), realized by femtosecond (fs) laser fabrication of high aspect ratio microstructure mold followed by mold transferring on black paint coating. The SBP exhibits extremely low hemispheric reflectance (R < 1.2%) in the solar spectrum at a normal incident angle; even at an 80° incident angle, the SBP also has good anti-reflection performance (R < 9%). Based on such properties, we further show the enhanced solar-thermal performance over commercial black paints. Our approach holds promises for scalable and cost-effective manufacturing of ultrablack surface, with potential applications in solar-thermal conversion efficiency improvement and space optical system stray light suppression.

Wood-based superblack

Light is a powerful and sustainable resource, but it can be detrimental to the performance and longevity of optical devices. Materials with near-zero light reflectance, i.e. superblack materials, are sought to improve the performance of several light-centered technologies. Here we report a simple top-down strategy, guided by computational methods, to develop robust superblack materials following metal-free wood delignification and carbonization (1500 °C). Subwavelength severed cells evolve under shrinkage stresses, yielding vertically aligned carbon microfiber arrays with a thickness of ~100 µm and light reflectance as low as 0.36% and independent of the incidence angle. The formation of such structures is rationalized based on delignification method, lignin content, carbonization temperature and wood density. Moreover, our measurements indicate a laser beam reflectivity lower than commercial light stoppers in current use. Overall, the wood-based superblack material is introduced as a mechanically robust surrogate for microfabricated carbon nanotube arrays.