Mantis shrimp eye inspires camera that senses colour and polarisation

The bioinspired imager can potentially improve early cancer detection and help provide a new understanding of underwater phenomena, said researchers from the University of Illinois.

"The animal kingdom is full of creatures with much more sensitive and sophisticated eyes than our own," said Viktor Gruev , a University of Illinois professor of electrical and computer engineering and co-author of the new study. "These animals perceive natural phenomena that are invisible to humans.

"Polarisation of light - that is, the direction of oscillation of light as it propagates in space - is one such example. While most of us are familiar with polarised sunglasses, which simply remove glare, many animals use polarized vision as a covert communication channel, to find food, or even to navigate by sensing polarisation patterns in the sky."

The mantis shrimp is said to possess one of the most sophisticated eyes in nature. Compared with human vision, which has three different types of colour receptors, the mantis shrimp has 16 different plus six polarisation channels, Gruev said.

Gruev and graduate student Missael Garcia led an effort to replicate the shrimp's visual system using some basic physical concepts. They report their findings in the journal Optica.

"Nature has constructed the mantis shrimp eye in such a way that photosensitive elements are vertically stacked on top of each other," Gruev said. This stacking allows for absorption of shorter wavelengths, such as blue light, in the shallow photoreceptors and red light in the deeper receptors. The photoreceptors are organized "in a periodic fashion at the nanoscale that allows them to also 'see' the polarised properties of light," he said.

"The same laws of physics that apply to the mantis visual system also apply to silicon materials, the material used to build our digital cameras" Garcia said. "By stacking multiple photodiodes on top of each other in silicon, we can see colour without the use of special filters. And by combining this technology with metallic nanowires, we effectively have replicated the portion of the mantis shrimp visual system that allows it to sense both colour and polarisation."

This combination of silicon photodetectors and nanomaterials allowed the Illinois research team to create a point-and-shoot colour-polarisation camera. The applications for such cameras are wide-ranging, from early cancer detection to monitoring changes in the environment to decoding the covert communication channels that many underwater creatures appear to exploit, the researchers said.

In a previously published study by Gruev, a bioinspired polarisation sensor fitted to a colonoscope could detect the disordered nature of cancerous cells in the human colon.

"By mimicking the mantis shrimp visual system, we have created a unique camera that can be used to improve the quality of our lives," Gruev said. "The notion that we can detect early formation of cancer is what is driving this research forward. The cost of this technology is less than $100, which will enable quality health care in resource-limited places around the world."