A new camera, inspired by the eye of the mantis shrimp, can sense polarisation as well as colour, meaning it can potentially improve early cancer detection and help provide a new understanding of underwater phenomena.
“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.
“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 polarised vision as a covert communication channel, to find food, or even to navigate by sensing polarisation patterns in the sky.”
He says the mantis shrimp possesses 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 types of colour receptors and six polarisation channels.
“Nature has devised materials such that different colours of light penetrate at different depths,” said Gruev.
“If we shine a blue laser and a red laser on the tip of our finger, we can only observe the red light on the other side of the finger. This is because the red light can penetrate deeper in the tissue. Nature has constructed the mantis shrimp eye in such a way that photosensitive elements are vertically stacked on top of each other. 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.”
His team realised the same laws applied to silicon materials and, by stacking multiple photodiodes on top of each other, they were able to see colour without the use of special filters. By combining this technology with metallic nanowires, they effectively replicated the portion of the mantis shrimp visual system that allows it to sense both colour and polarisation.
[Prof Viktor Gruev (right) with graduate student Missael Garcia. Photo: Brian Stauffer/UIllinois]