Shrimp Inspires New Breed of Light Sensors

Experimental prototype of the shrimp sensor. The tandem structure consists of 6 polarization-sensitive organic photovoltaics and 4 polymer retarder films cascaded in series along the same optical axis. (Source: A. Altaqui)

Inspired by the eyes of mantis shrimp, researchers have developed a new kind of optical sensor that is small enough to fit on a smartphone but is capable of hyper­spectral and polari­metric imaging. “Lots of arti­ficial intelligence programs can make use of data-rich hyper­spectral and polari­metric images, but the equipment necessary for capturing those images is currently somewhat bulky,” says Michael Kudenov at North Carolina State University. “Our work here makes smaller, more user friendly devices possible. And that would allow us to better bring those AI capa­bilities to bear in fields from astronomy to biomedicine.”

In the context of this research, hyper­spectral imaging refers to technologies that can break down the visible wavelengths of light into more narrow bands. The human eye can’t distinguish between these slight variations in color, but computers can – making hyper­spectral imaging valuable for tasks such as determining the chemical compo­sition of objects in the image. Polarimetry refers to the measurement of polari­zation in light, which is data that can be used to determine the surface geometry of an object in the image. For example, is the surface rough or smooth? And what is the angle of the surface relative to the light source?

While there are larger devices that are capable of capturing hyper­spectral and polari­metric images, smartphone-sized imaging techno­logies have run into signi­ficant challenges. For example, the design of cell phone camera techno­logies results in very slight errors in the alignment of the different wavelengths of light in the final image. The result is not a big deal for taking family photos, but is problematic for scientific image analysis. And the problem is exacer­bated when a camera can capture more colors, as is the case with hyper­spectral techno­logies. The creators of the new light sensors were inspired by the eyes of mantis shrimp, which are excep­tionally good at accurately capturing subtle gradations of color. So, the researchers created an organic electronic sensor that mimics the mantis shrimp’s eye. It’s called the Stomatopod Inspired Multi­spectral and POLari­zation sensitive (SIMPOL) sensor.

The researchers developed a prototype SIMPOL sensor that can simul­taneously register four spectral channels and three polari­zation channels. By comparison, the charge-coupled devices used in smart­phones have only three spectral imaging sensors, which detect red, green, and blue; and only two polari­zation channels. In addition, the SIMPOL prototype can measure the four color channels and three polarization channels at one point, whereas CCDs rely on imaging sensors spread across several points. While only a proof of concept, the researchers used modeling simu­lations to determine that the design could be used to create detectors capable of sensing up to 15 spatially registered spectral channels.

“SIMPOL’s color channels can discern spectral features 10 times narrower than typical imaging sensors; in other words, it is 10 times more precise,” Kudenov says. “Our work demons­trates that it is possible to create small, efficient sensors that can simul­taneously capture hyper­spectral and polari­metric images,” says Brendan O’Connor. “I think this opens the door to a new breed of organic electronic sensing techno­logies.” (Source: NCSU)

Reference: A. Altaqui et al.: Mantis shrimp–inspired organic photodetector for simultaneous hyperspectral and polarimetric imaging, Sci. Adv. 7, eabe3196 (2021); DOI: 10.1126/sciadv.abe3196

Link: Physical Electronics, Photonics & Magnetics, Dept. of Electrical and Computer Engineering, North Carolina State University, Raleigh, USA

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