Tiny spider with a rainbow back could spawn wealth of optical technologies

3 Jan 2018

An Australian peacock spider. Image: Jurgen Otto/Flickr (CC BY-NC-ND 2.0)

Nature’s smallest rainbow, contained within the body of a tiny spider, could spawn a whole range of new optical technologies.

While you might not spot the tiny Australian peacock spider at first glance, at only 5mm in size, its body plays host to a truly dazzling sight that is not only impressive to look at, but could aid our efforts in the life sciences and biotechnology sectors.

The male variant of the Maratus robinsoni species of peacock spider displays diverse and intricate body colourations, patterns and movements during courtship. This is the first known instance of a male species using the entire spectrum of the rainbow to entice a female.

In an attempt to understand how the spider creates such a dazzling display, a team of international researchers led by Dr Bor-Kai Hsiung from the University of California San Diego has recently published a paper in Nature Communications documenting its discovery.

The team investigated the spider’s photonic structures using techniques that included light and electron microscopy, hyperspectral imaging, imaging scatterometry and optical modelling to generate hypotheses about how the spider can generate such intense rainbows.

Rainvow pattern

Light micrograph of rainbow patterned Maratus robinsoni scales. Image: Dr. Bor-Kai Hsiung

Not possible with human technology

Using nano 3D printing to fabricate different peacock spider prototypes, the team found that the intense rainbow iridescence emerged from specialised abdominal scales on the spiders.

These incredible scales combine an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface, allowing for the separation and isolation of light into its component wavelengths at angles far in advance of what is possible with human technology.

With this new knowledge of how the spider creates such a spectacle, the team believes it can unlock more of its secrets to bring major advances to optical and colour technologies.

“As an engineer, what I found fascinating about these spider structural colours is how these long-evolved complex structures can still outperform human engineering,” said Dr Radwanul Hasan Siddique, co-author of this research.

“Even with high-end fabrication techniques, we could not replicate the exact structures. I wonder how the spiders assemble these fancy structural patterns in the first place!”

This marks the second rainbow-related breakthrough of the past few days after another team of researchers successfully developed the first single lens that can focus the entire visible spectrum of light – including white light – in the same spot and in high resolution.

An Australian peacock spider. Image: Jurgen Otto/Flickr (CC BY-NC-ND 2.0)

Colm Gorey was a senior journalist with Silicon Republic