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Zhao B, Shi X, Khakalo S, Meng Y, Miettinen A, Turpeinen T, Mi S, Sun Z, Khakalo A, Rojas OJ, Mattos BD. Wood-based superblack. Nat Commun 2023; 14:7875. [PMID: 38052773 DOI: 10.1038/s41467-023-43594-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/14/2023] [Indexed: 12/07/2023] Open
Abstract
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.
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Affiliation(s)
- Bin Zhao
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Espoo, FI-02150, Finland
| | - Xuetong Shi
- Bioproduct Institute, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Sergei Khakalo
- Department of Civil Engineering, School of Engineering, Aalto University, Espoo, FI-02150, Finland
- Integrated Computational Materials Engineering, VTT Technical Research Centre of Finland Ltd, Espoo, FI-02044, Finland
| | - Yang Meng
- Faculty of Chemical Engineering, Kunming University of Science and Technology, Kunming, 650500, PR China
| | - Arttu Miettinen
- Department of Physics, University of Jyvaskyla, Jyväskylä, FI-40014, Finland
| | - Tuomas Turpeinen
- Fiber Web Processes, VTT Technical Research Centre of Finland Ltd, Jyväskylä, FI-40400, Finland
| | - Shuyi Mi
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
| | - Zhipei Sun
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
- QTF Centre of Excellence, Department of Applied Physics, Aalto University, Espoo, FI-02150, Finland
| | - Alexey Khakalo
- Cellulose Coatings and Films, VTT Technical Research Centre of Finland Ltd, Espoo, FI-02044, Finland
| | - Orlando J Rojas
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Espoo, FI-02150, Finland.
- Bioproduct Institute, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
| | - Bruno D Mattos
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Espoo, FI-02150, Finland.
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Does Structural Color Exist in True Fungi? J Fungi (Basel) 2021; 7:jof7020141. [PMID: 33669274 PMCID: PMC7920071 DOI: 10.3390/jof7020141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 02/12/2021] [Accepted: 02/12/2021] [Indexed: 12/25/2022] Open
Abstract
Structural color occurs by the interaction of light with regular structures and so generates colors by completely different optical mechanisms to dyes and pigments. Structural color is found throughout the tree of life but has not, to date, been reported in the fungi. Here we give an overview of structural color across the tree of life and provide a brief guide aimed at stimulating the search for this phenomenon in fungi.
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Ultra-black Camouflage in Deep-Sea Fishes. Curr Biol 2020; 30:3470-3476.e3. [PMID: 32679102 DOI: 10.1016/j.cub.2020.06.044] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/25/2020] [Accepted: 06/12/2020] [Indexed: 12/27/2022]
Abstract
At oceanic depths >200 m, there is little ambient sunlight, but bioluminescent organisms provide another light source that can reveal animals to visual predators and prey [1-4]. Transparency and mirrored surfaces-common camouflage strategies under the diffuse solar illumination of shallower waters-are conspicuous when illuminated by directed bioluminescent sources due to reflection from the body surface [5, 6]. Pigmentation allows animals to absorb light from bioluminescent sources, rendering them visually undetectable against the dark background of the deep sea [5]. We present evidence suggesting pressure to reduce reflected bioluminescence led to the evolution of ultra-black skin (reflectance <0.5%) in 16 species of deep-sea fishes across seven distantly related orders. Histological data suggest this low reflectance is mediated by a continuous layer of densely packed melanosomes in the exterior-most layer of the dermis [7, 8] and that this layer lacks the unpigmented gaps between pigment cells found in other darkly colored fishes [9-13]. Using finite-difference, time-domain modeling and comparisons with melanosomes found in other ectothermic vertebrates [11, 13-21], we find the melanosomes making up the layer in these ultra-black species are optimized in size and shape to minimize reflectance. Low reflectance results from melanosomes scattering light within the layer, increasing the optical path length and therefore light absorption by the melanin. By reducing reflectance, ultra-black fish can reduce the sighting distance of visual predators more than 6-fold compared to fish with 2% reflectance. This biological example of efficient light absorption via a simple architecture of strongly absorbing and highly scattering particles may inspire new ultra-black materials.
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