Silica Nanospheres as Photonic Nanostructure Found in the ‘Disco’ Clam Ctennoides Ales
Scientists from UC Berkeley have recently discovered that a strange naturally occurring bright display of the ‘disco’ or ‘electric’ clam Ctenoides ales is actually a photonic display created by a layer of silica nanospheres. The display functions solely by reflecting light.
An article was published in the Journal of The Royal Society titled “A Dynamic Broadband Reflector Built from Microscopic Silica Spheres in the ‘Disco’ Clam Ctenoides Ales“, where the researchers shared their findings.
Laboratory elemental analysis of the reflective nanospheres showed that they are indeed composed of amorphous silica. Both the outer shells and the cores are composed of silica. Silica nanospheres are secreted by the animal and used as a light scattering structure in a behavior modulated reflective photonic display.
The measurements show that the diameter of the silica nanospheres is at around 300nanometers, an optimal particle size for scattering visible light, especially the shorter blue-green wavelengths of 400-500nm that predominate at 3-50m underwater, which is typically the clam’s habitat. In addition to the diameter, the highly organized packing structure of the nanospheres aid in the scattering of the visible light at the shorter wavelengths.
The display is so bright that it has been mistakenly thought of as bioluminescent, but the findings show that it is actually based on light scattered by photonic nanostructures.
Silica has a high index of refraction at n=1.43 at 589nm.
This study is extremely interesting to scientists in many different fields because it opens their minds up to many creative uses of silica nanospheres that have not been known before. The findings show a practical way to manipulate light in low light situations. Among its other advantages, silica, similar to glass, is a very durable material, with high melt point. Using silica nanospheres in tightly packed arrays to create photonic nanostructures seems like a great idea.
Highly precise and spherical silica nanospheres with narrow size distribution, diameters around 300nm and sphericity of greater than 99% in dry powder from can be purchased from CosphericNano—a new website specializing in precise silica nanospheres.
Silane and Fluorochemical Coated Glass Spheres
Solid glass imparts visual and material benefits that cannot be replicated when spheres are made of other materials such as ceramics or polymerics, aluminum oxides, or silicas and mineral fillers. Solid glass refracts [bends] and reflects light. Most ceramics [with exceptions] do not transmit light or exhibit specular [mirror-like] reflection due to their internal crystalline structures and surface irregularities. Instead of being reflected back, the light is “trapped” in the structure and emitted as diffuse or scattered reflectance, which is not as strong or direct as light transmitted through glass, which produces mirror-like reflectance. Prizmalite glass spheres distributed by Cospheric offer off the shelf pre-coated spheres for enhancing these effects.
Silane coated solid glass spheres with increased hydrophobicity are offered to improve the dispersion of spheres throughout paints and coatings. Silane coated spheres are not recommended for pure water solutions as the spheres will be too hydrophobic to wet.
Fluorochemical Coating is available for paint and coating applications where it is desired to bring the spheres to the top of the surface of the coating. This is best used in applications where retro reflectance is desired.
The following products are offered in both Silane and Fluorochemical Coating.
P2011SL 3-6um mean diameter solid soda lime glass
P2015SL 8-12um mean diameter solid soda lime glass
P2050SL 35-45um mean diameter solid soda lime glass
P2075SL 65-75um mean diameter solid soda lime glass
P2453BTA 40-60um mean diameter solid barium titanate glass with aluminum shell.
- Act as mini-magnifying glasses to deliver visually truer color
- Clarify and magnify the visual impact of pigments and metallic flakes
- Create a richer, wetter, deeper look
- Visually extend expensive color-shift pigments to create cost-effective new looks
- Prop up other pigments, mica and aluminum flakes
- Increase exposed surface area and visual impact
- Facilitate even dispersion of colorants and reflectors
- Are anti-mottling agents that enhance visual consistency
- Act as mini-ball bearings to improve material flow and reduce flow lines
- Provide color consistency from all viewing angles
High Index of Refraction Retroreflective Glass Microspheres
Barium Titanate Glass Microspheres are excellent for use as a functional retro reflective additive to paints and coatings. Spheres with sizes of about 50 micron (~0.002 inches) mean diameter provide a small enough size for most coatings while offering a large enough size to reflective a significant amount of light. Barium Titanate Glass Spheres are offered in both partially aluminum coated retro-reflective version for addition into transparent coatings, or as uncoated glass spherical powder for uses in colored paints.
For those applications calling for a high density filler, barium titanate glass spheres offer a density of 4.5g/cc, that is almost double that of the more common soda lime glass spheres. In addition to a high density, barium titanate glass spheres have a hardness of about 55-65 on the Gardner scale and a crush strength of over 30,000 psi (207 Mpa) making these spheres very durable in high wear environments.