The mantis shrimp’s wiggling eyes inspire new optical sensors

Smartphone cameras have improved dramatically since the first camera phone was introduced in 1999, but they are still subject to minor errors in the alignment of different wavelengths of light in the final image. 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 in the eyes of the mantis shrimp, which inspired researchers at North Carolina State University (NCSU) to develop a new type of optical sensor. The sensor is small enough for smartphone applications, but it is also capable of splitting visible light wavelengths into narrower bands than current smartphone cameras can handle and capturing polarized light, according to a recent article published in the journal Science Advances.

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

Mantis shrimp have three “pseudopupils 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 center of the eye, also called the middle band. to detect specific wavelengths of light or polarized light. The first four rows are dedicated to the first, including UV light, while the last two rows are lined with tiny hairs that allow the latter to be detected.

Each compound eye can move independently and thus also has independent depth perception, as about 70 percent of each eye focuses on the same point in space. This makes the eyes act a bit like scanning a photo; Mantis shrimp constantly move their eyes to scan their surroundings, see a color band, move a row of ommatidia, and repeat the scan.

Those properties inspired the NCSU researchers to base the design for their new organic light sensor on the structure of mantis shrimp. Called the Stomatopod-inspired Multispectral and POLarisation Sensitive (SIMPOL) sensor, it contains elements (six polarization sensitive organic photovoltaic cells and four polymer retarder films) stacked vertically along a single optical axis, much like the rows of ommatidia in the mantis shrimp. on a single pixel. Thus, it can detect hyperspectral and polarizing light at the same time.

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

The researchers built a proof-of-concept prototype of the SIMPOL sensor and tested its capabilities in the lab. They found that while the standard smartphone CCD cameras use three spectral image sources for red, green, and blue light, the SIMPOL can handle four spectral channels and three polarization channels simultaneously. Modeling simulations suggest the team could further improve its design to build detectors capable of detecting as many as 15 spectral channels simultaneously.

“Many artificial intelligence (AI) programs can use data-rich hyperspectral and polarimetric images, but the equipment needed to capture those images is currently quite bulky,” said study co-author Michael Kudenov, also of NCSU. “Our work here enables smaller, more user-friendly devices. And that would allow us to better apply those AI capabilities in fields from astronomy to biomedical medicine.”

DOI: Science Advances, 2021.10.1126 / sciadv.abe3196 (About DOIs).