Mantis shrimp googly eyes inspire new optical sensors

Smartphone cameras have improved dramatically since the introduction of the first camera-equipped cell phone in 1999, but they are still prone to tiny errors in the alignment of the different wavelengths of light in the image. final. That’s not a problem for your average Instagram selfie, but it’s far from ideal when it comes to scientific image analysis, for example.

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

Human eyes have three photoreceptors to detect red, green, and blue light. Dogs only have two photoreceptors (green and blue), while birds have four, including one for detecting ultraviolet (UV) light. Octopuses, on the other hand, can detect polarized light. But mantis shrimp (aka stomatopods) have the most complex eyes of all – they can have between 12 and 16 individual photoreceptors and can thus detect visible, UV and polarized light.

Mantis shrimp have three pseudo-pupils stacked on top of each other. There are tens of thousands of clumps of photoreceptor cells called ommatidia, similar to the eyes of flies. Six rows of ommatidia in the middle of the eye, called the middle band, are each capable of detecting either specific wavelengths of light or polarized light. The first four rows are devoted to the first including UV light, while the last two rows are lined with tiny hairs which confer the ability to sense the second.

Each compound eye can move independently and thus enjoys independent depth perception, as around 70% of each eye is focused on the same point in space. For this reason, the eyes work much like scanning a photograph; mantis shrimp constantly move their eyes to scan their surroundings, spot a band of color, move a row of ommatidia, and repeat the scan.

These properties inspired NCSU researchers to base the design of their new organic light sensor on the structure of mantis shrimp eyes. Dubbed the SIMPOL (Stomatopod Inspired Multispectral and POLarization sensitive) sensor, it includes elements (six polarization-sensitive organic photovoltaics and four polymer retardant films), stacked vertically along a single optical axis, just like the rows of ommatidia in mantis shrimp – all on one pixel. Thus, it can simultaneously detect hyperspectral and polarization light.

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

Researchers built a proof-of-concept prototype of the SIMPOL sensor and tested its capabilities in the laboratory. They found that although standard smartphone CCD cameras use three spectral imaging sources for red, green and blue light, SIMPOL can handle four spectral channels and three polarization channels, all at the same time. Modeling simulations suggest that the team could further improve their design to build detectors capable of detecting up to 15 spectral channels simultaneously.

“Many artificial intelligence (AI) programs can use data-rich hyperspectral and polarimetric images, but the equipment needed to capture these images is currently a bit cumbersome,” said co-author Michael Kudenov, also of NCSU. . “Our work here makes smaller, more user-friendly devices possible. And that would allow us to better exploit these artificial intelligence capacities in fields ranging from astronomy to biomedicine.

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