The googly eyes of the mantis shrimp inspire new optical sensors

Smartphone cameras have improved dramatically since the first camera-equipped phone was introduced in 1999, but they are still subject to small errors in the alignment of different wavelengths of light in the final image. This is not a concern for your average Instagram selfie, but it is far from ideal when it comes to scientific image analysis, for example.

Nature apparently provided a solution in the eyes of the mantis shrimp, which inspired North Carolina State University (NCSU) researchers to develop a new type of optical sensor. The sensor is small enough for smartphone applications, but is also capable of breaking down wavelengths of visible light into narrower bands than current smartphone cameras can drive, as well as capturing polarized light, according to a recent article in the journal Science Advances has been published.

Human eyes have three photoreceptors to detect red, green and blue light. Dogs have only two photoreceptors (green and blue), while birds have four, one of which is for the detection of ultraviolet (UV) light. Octopuses, meanwhile, can detect polarized light. Mantis shrimp (also known as stomatopods) have the most complex eyes of all: they can have between 12 and 16 individual photoreceptors and can therefore detect visible, UV and polarized light.

Mantis shrimp have three pseudo-pupils stacked on top of each other. There are tens of thousands of clusters of photoreceptor cells called ommatidia, similar to the eyes of flies. Six rows of ommatidia in the middle of the eye, known as the midrib, can each have specific wavelengths of light polarized light detection.The first four rows are devoted to the former, including UV light, while the last two rows are lined with small hairs that give the ability to detect the latter.

Each composite eye can move independently and thus also boasts an independent depth perception, as approximately 70 percent of each eye focuses on the same point in space. As a result, the eyes function a bit like scanning a photo; Mantis shrimp constantly move their eyes to scan their surroundings, see a ribbon, move a row of ommatidia, and repeat the scan.

These features inspired the NCSU researchers to base the design of their new organic light sensor on the structure of mantis shrimp eyes. Called the Stomatopod Inspired Multispectral and POLarisation sensitive (SIMPOL) sensor, it contains elements (six polarization-sensitive organic photovoltaic and four polymer retarder films), stacked vertically along a single optical axis, just like the rows of ommatidia in the mantis shrimp – all on a single pixel. It can therefore detect hyperspectral and polarization light simultaneously.

“Our work demonstrates that it is possible to create small, efficient sensors that can capture hyperspectral and polarimetric images simultaneously,” said NCend co-author Brendan O’Connor. “I think it opens the door to a new kind of organic electronic sensing technologies.”

The researchers built a proof of the concept prototype of the SIMPOL sensor and tested its capabilities in the laboratory. They found that although standard CCD cameras for smartphones use three spectral image sources for red, green and blue light, the SIMPOL can handle four spectrum channels and three polarization channels simultaneously. Modeling simulations suggest that the team can further improve its design to build detectors that can detect up to 15 spectrum channels simultaneously.

“Many artificial intelligence (AI) programs can use data-rich hyperspectral and polarimetric images, but the equipment needed to record the images is currently somewhat bulky,” said co-author Michael Kudenov, also of NCSU. “Our work here enables smaller, more user-friendly devices. And it will enable us to better leverage the AI ​​capabilities in fields from astronomy to biomedicine.”

DOI: Science Advances, 2021. 10.1126 / sciadv.abe3196 (On DOIs).