Antireflective surface inspired from biology: A review

Han, Zhiwu; Wang, Z.; Feng, Xiaoming; Li, Bo; Mu, Zhengzhi; Zhang, J.Q.; Niu, Shichao; Liu, Ren

doi:10.1016/j.bsbt.2016.11.002

Cited by 98 publications

(50 citation statements)

References 96 publications

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“…Figure 5c showing <1% reflectance (R) over the wavelength range λ = 200-800 nm on the urchin surface, compared to two control samples (bare Si and Si with 20 nm ZnO thin film). There have been previous reports on fabrication of nanostructured anti-reflective surfaces [6,11,[64][65][66][67][68][69][70]. Different techniques such as dry etching, wet etching, metal assisted etching, nanoimprint lithography, etching using O 2 plasma and inductively coupled plasma, optical lithography followed by etching etc.…”

Section: Resultsmentioning

confidence: 99%

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Tripathy

Wąsik

Sreedharan

et al. 2018

Colloids and Interfaces

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Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report the simple fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, µm-long, tapered nanoneedles radiating from the urchin center. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of "infant" urchins at the early growth stage and subsequent progressive increases in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. ε-Zn(OH) 2 orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth times were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins-with spiky nanoneedles and at high surface density-on Si substrates was demonstrated. First, bacteria colonization was found to be suppressed on the surface after 24 h incubation in gram-negative Escherichia coli (E. coli) culture, in contrast to control substrates (bare Si and Si sputtered with a 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle ∼ 0 • , could be rendered superhydrophobic with a simple silanization step, characterized by an apparent water contact angle θ of 159 • ± 1.4 • and contact angle hysteresis ∆θ < 7 • . The dynamic superhydrophobicity of the surface was demonstrated by the bouncing-off of a falling 10 µL water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200-800 nm. The ZnO urchins with a unique morphology fabricated via a simple route at room temperature, and readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations.

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Section: Resultsmentioning

confidence: 99%

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Tripathy

Wąsik

Sreedharan

et al. 2018

Colloids and Interfaces

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“…In There have been previous reports on fabrication of nanostructured anti-reflective surfaces 6,11,[59][60][61][62][63][64][65] .…”

Section: Resultsmentioning

confidence: 99%

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Tripathy¹,

Wąsik²,

Sreedharan³

et al. 2018

Preprint

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Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report facile fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, μm-long, tapered nanoneedles radiating from the urchin centre. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of “infant” urchins at the early growth stage and subsequent progressive increase in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. ε-Zn(OH)2 orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth time were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins—with spiky nanoneedles and at high surface density—on Si substrates was demonstrated. First, bacteria colonisation was found to be suppressed on the surface after 24 h incubation in Gram-negative E. coli culture, in contrast to control substrates (bare Si and Si sputtered with 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle ~0°, could be rendered superhydrophobic with a simple silanization step, characterised by a water static contact angle θ of 159° ± 1.4° and contact angle hysteresis ∆θ < 7°. The dynamic superhydrophobicity of the surface was demonstrated by bouncing-off of a falling 10 μL water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200–800 nm. The ZnO urchins with unique morphology via a facile fabrication route at room temperature, readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations.

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“…In reference [31], the formation of a fine structure on the hair surface is described. When the size of the fine structure is less than the wavelength of visible light, the reflection at the surface is suppressed and the apparent hair color is enhanced, similar to the moth-eye effect [32].…”

Section: Effect Of Surface Roughness (Cuticle)mentioning

confidence: 93%

Hair Structures Affecting Hair Appearance

Nagase

2019

Cosmetics

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Optical factors affecting hair appearance are reviewed based on hair structures from macroscopic to microscopic viewpoints. Hair appearance is the result of optical events, such as reflection, refraction, scattering, and absorption. The effects of hair structures on such optical events are summarized and structural conditions for hair appearance are considered. Hair structures are classified into the following: the alignment of multiple hair fibers, the cross-sectional shape of the hair fiber, and the microstructures of hair fiber (cuticle, cortex, and medulla). The alignment of multiple hair fibers is easily affected by the existence of meandering fibers and their alignment along hair length becomes less-synchronized. The less-synchronized orientation of multiple fibers causes the broadening of the apparent reflection and luster-less dull impression. The cross-sectional shape of hair fiber affects light reflection behavior. Hair fibers with elliptical cross-section show glittering colored light based on total reflection in the hair. The scaly structures of cuticles at the surface of hair are often uplifted and cause light scattering, and then affect hair luster. The porous structure of the cortex and medulla in hair fiber can cause light scattering and affect hair luster and color. The above phenomena suggest that important factors for hair appearance are the alignment of multiple hair fibers, appropriate cross-sectional shape, ordered scaly structure, and pore-less internal structure.

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Antireflective surface inspired from biology: A review

Cited by 98 publications

References 96 publications

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

Hair Structures Affecting Hair Appearance

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