Researchers have looked into nature for inspiration, understanding the mechanisms animals, insects and plants use to capture and process light and then designing next generation optoelectronics devices and systems like light-emitting diodes (LEDs), sensors and materials. Biomimicry has led to the development of several naturally inspired structures, such as curved imaging sensors or compound lens arrays.
Inspired from fireflies, Researchers from belgium enhanced the efficiency of LEDs and Korean researchers designed efficient OLEDs. GE researchers have fabricated Nanostructures based gas sensors following a design of natural Morpho butterfly wings and Researchers from University of Pennsylvania, have employed liquid crystals to create compound lenses similar to those found in nature.
Nature provides many examples of optical structures whose properties arise from an intricate morphology. The brilliant colors seen in butterfly wings, beetle carapaces, and peacock feathers, for example, are due in large part to their complex structure, says DARPA. These hierarchical structures, scaling from micron to nanometer level, achieve remarkable optical functionality through a complex combination of scattering, reflection, and absorption phenomena. Fabrication of advanced photonic devices can take inspiration from the fault tolerance of these structures, nature’s ability to manufacture at the nanoscale, and the hierarchical structurally dependant optical properties.
Inspired by the visual system of the mantis shrimp—among the most complex found in nature–researchers have created a new type of camera that could greatly improve the ability of cars to spot hazards in challenging imaging conditions.
The new camera accomplishes this feat by detecting a property of light known as polarization and featuring a dynamic range about 10,000 times higher than today’s commercial cameras. Dynamic range is a measure of the brightest and darkest areas a camera can capture simultaneously. With these, the camera can see better in driving conditions such as the transition from a dark tunnel into bright sunlight or during hazy or foggy conditions.
In Optica, The Optical Society’s journal for high impact research, the researchers describe the new camera, which could be mass-produced for as little as $10 apiece. The researchers say the new camera would enable cars to detect hazards, other cars and people three times farther away than color cameras used on cars today.
Military is also interested in bioinspired photonics , cephalopods invertebrates have emerged as exciting sources of inspiration for futuristic adaptive camouflage and shapeshifter-like technologies which can disguise an object or physically changing it to resemble something entirely different. Bio-inspired nanostructured sensors are enabling faster, more selective chemical and explosives detection.
The natural world displays marvelous examples of light manipulation, processing, and light-driven actuation. Nature’s most vivid colours rely on ordered, quasi-ordered, and disordered structures with lattice constants or scattering elements whose sizes are on the order of the wavelength of visible radiation. Knowledge of the interplay between the morphology, composition, and optical appearance of biological photonic systems can provide inspiration for novel artificial photonic materials.
The synergy between advanced imaging techniques, micro- and nanofabrication tools, including colloidal assembly and electromagnetic wave predictive tools has been enabling to the replication of these naturally occurring structures with impressive demonstrations of photonic crystal lattices, aberration-free imaging systems, curvilinear optics, implantable and/or injectable micro- and nanoscale optical interfaces, among many others, writes Fiorenzo G. Omenetto, Associate Editor APL photonics.
Perhaps one of the most daunting technical challenges to emulate lies in Nature’s ability to form materials with dimensional control over multiple orders of magnitude that span from the nano-to the macroscale. These systems have very elegant hierarchical geometries that are mostly formed in bottom-up fashion, through directed assembly. Of special interest are optical structures that are dynamic and adaptable, embedding active biochemical cues that allow them to react either physiologically or mechanically.
An approach of recent interest involves co-opting the same materials used by Nature to construct photonic systems while studying the assembly processes that lead to the formation of these structures. Some examples include photonic structures based on structural proteins such as keratins or silks, polysaccharides such as cellulose or starch (e.g., PLA, chitosan, or zein), or structures that assemble within living organisms such as lipids within cells, collagens, guanine crystals, and so on. The departure from inorganic materials in favor of naturally derived materials not only introduces the paradigm of bottom-up fabrication, but also new modalities of bulk-doping and controlled interactions between photons and biological matter in modalities that are not trivial to achieve otherwise.
The natural drive for survival, mating, resource harvesting, energy management, and environmental adaptation imposes functional constraints to naturally assembled structures which, more often than not, present multiple functions in a single geometry. The simple familiar example of butterfly wing iridescence provides not only a marvelous example of growth of a photonic crystal—it is accompanied by a light, multilayered, mechanically robust structure suitable for flight, which also uses its surface structure to repel dust and water, while assisting in the thermal regulation of the animal.
Multifunctional optical systems that are inspired by these paradigms are a direction of particular opportunity. Such convergence of function has started to develop in disciplines such as optofluidics, where photons and volumetric flow in macro- or microfluidic channels come together to play off of one another to add degrees of freedom for light modulation and light manipulation.
The connection to natural systems expands such degrees of freedom further: systems such as a plant leaves have the capacity to actuate in response to photon flux, reorient, and manage their nutrient transport, respiration, and metabolism, providing a multiscale fluidic network that is surrounded by a light responsive, adaptable environment. The fluidic network of plants has been permeated with organic electronics devices, opening the door for systems that leverage the sophistication of biological signaling and communication for next-generation energy harvesters, environmental sensors, or optical device templates.
One of the fundamental biological tenets is to grow materials rather than build them. While biomimicry has led to the development of several naturally inspired structures, such as curved imaging sensors or compound lens arrays, the opportunity to “grow” optics is looming on the horizon. With access and availability to new biotechnology tools paired with the existing micro- and nanoscale fabrication backbone, an expanded kit of materials of optical relevance can be obtained through genetic synthesis and modification.
An example is DNA origami that templates molecules into desired structures with nanoscale precision. While the use of genetic editing tools such CRISPR-Cas9 are widely covered in the literature for their medical promise, it is quite plausible that the same tools can be used to enhance functional outcomes of technical relevance such as increased luminescence or charge transport, for instance. A recent demonstration of this explored the manipulation of structural color in bacterial colonies through the isolation of the genetic code in control of their nanoscale assembly, exemplifying the possibility of “growing color.”
Using living components as enablers for photonics opens the door to many of the functional behaviors found in natural systems and vice versa, with opportunities in sensing, energy harvesting, photoconversion and photocatalysis, along with optically based transduction systems that can empower new distributed sensing approaches that will allow for deeper knowledge of complex natural systems while offering new strategies for photonics discovery, technological development, and manufacturing, writes Fiorenzo G. Omenetto, Associate Editor APL photonics.
Bioinspired Camera Could Help Self-Driving Cars See Better
“In a recent crash involving a self-driving car, the car failed to detect a semi-truck because its color and light intensity blended with that of the sky in the background,” said research team leader Viktor Gruev of the University of Illinois at Urbana-Champaign, USA. “Our camera can solve this problem because its high dynamic range makes it easier to detect objects that are similar to the background and the polarization of a truck is different than that of the sky.”
In addition to automotive applications, the researchers are exploring using the cameras to detect cancerous cells, which exhibit a different light polarization than normal tissue, and to improve ocean exploration.
“We are beginning to reach the limit of what traditional imaging sensors can accomplish,” said Missael Garcia, first author of the paper. “Our new bioinspired camera shows that nature has a lot of interesting solutions that we can take advantage of for designing next-generation sensors.”
Mimicking shrimp vision
Mantis shrimp, a grouping that includes hundreds of species worldwide, have a logarithmic response to light intensity. This makes the shrimp sensitive to a high range of light intensities, allowing them to perceive very dark and very bright elements within a single scene.
To achieve a similarly high dynamic range for their new camera, the researchers tweaked the way the camera’s photodiodes convert light into an electrical current. Instead of operating the photodiodes in reverse bias mode — which is traditionally used for imaging — the researchers used forward bias mode. This changed the electrical current output from being linearly proportional to the light input to having a logarithmic response like the shrimp.
For the polarization sensitivity, the researchers mimicked the way that the mantis shrimp integrates polarized light detection into its photoreceptors by depositing nanomaterials directly onto the surface of the imaging chip that contained the forward biased photodiodes. “These nanomaterials essentially act as polarization filters at the pixel level to detect polarization in the same way that the mantis shrimp sees polarization,” said Gruev.
Although traditional imaging sensor fabrication processes can be used to make the sensors, they are not optimized for making photodiodes that operate in a forward bias. To compensate, the researchers developed additional processing steps to clean up the images and to improve the signal to noise ratio.
Taking the camera on the road
After testing the camera under different light intensities, colors and polarization conditions in the lab, the researchers took the camera into the field to see how well it operated in shadows as well as in bright conditions. “We used the camera under different driving lighting conditions such as tunnels or foggy conditions,” said Tyler Davis, a member of the research team. “The camera handled these challenging imaging conditions without any problems.”
The researchers are now working with a company that manufactures air bags to see if the new camera’s high dynamic range and polarization imaging capability can be used to better detect objects to either avert a collision or deploy the air bag a few milliseconds earlier than is currently possible.
Exploring the ocean
The researchers also received funding to use the new imaging system to make small GoPro-like cameras that could be used to explore the ocean. While GPS systems such as those in cell phones do not work under water, the new camera’s polarization detection capability allows it to use the polarization of sunlight in water to calculate location coordinates. In addition, the camera’s high dynamic range could be used to record high quality images under water.
“We are coming full circle by taking the camera, which was inspired by mantis shrimp, to different tropical oceans to learn more about how this shrimp behaves in its natural habitat,” said Gruev. “They live in shallow waters and bury themselves under corals or in little burrow. This creates a challenging high dynamic range imaging situation because there’s a lot of light in the water but dim conditions inside the holes.”
Fireflies inspire 61% brighter Organic light-emitting diodes (OLEDs)
Jae-Jun Kim from the Korea Advanced Institute of Science and Technology and colleagues inspired from firefly hierarchical lantern ultrastructures developed a highly efficient organic light-emitting diode (OLED) prototype. The external quantum efficiency (EQE) of the bioinspired OLEDs was enhanced by up to 61%. The bio-inspired OLED also emits light at a broader angle, so could be used in energy-efficient televisions and computer screens with larger viewing angles.
Fireflies have long been the subject of photonics researchers. Their glowing rears are the product of a chemical reaction within special cells called photocytes. A cuticle, or skin, lies atop the photogenic layer, and the light shines through it, signalling to other fireflies that they’re ready to mate. To minimise the amount of light reflected back into the body, firefly lanterns have a layer below the photocytes which bounces light back up and out of the insect.
The hierarchical structures are comprised of longitudinal nanostructures and asymmetric microstructures, which were successfully replicated using geometry-guided resist reflow, replica molding, and polydimethylsiloxane (PDMS) oxidation.
“The highly efficient light extraction and wide-angle illumination suggest how the hierarchical structures likely improve the recognition of firefly optical courtship signals over a wide-angle range. At the same time, the biologically inspired designs provide a new paradigm for designing functional optical surfaces for lighting or display applications,” write authors.
Fireflies inspire increase in efficiency of LED design by 55%
Researchers at the university of Namur(Belgium), studied the surface pattern found on the abdomen of fireflies and applied it in design of surface coating on LED which increased its light extraction efficiency by 55%. Annick C K Bay, a doctoral student and her colleagues, modeled the emission of 560 nm light,close to its peak emission wavelength from the abdomen of fireflies of genyus Photuris. They found that light extraction from the abdomen is increased due to corrugated surface formed from overlapping scales.
The researchers are hopeful that in few years LED production methods would be able to adopt these enhancements with only minor modifications and achieve high energy efficiency.
Compound insect eyes inspire digital camera which can take wide angle photos
The compound eyes found in insects and some sea creatures are marvels of evolution. There, thousands of lenses work together to provide sophisticated information without the need for a sophisticated brain. Human artifice can only begin to approximate these naturally self-assembled structures, and, even then, they require painstaking manufacturing techniques
Now, engineers and physicists at the University of Pennsylvania, have employed liquid crystals to create compound lenses similar to those found in nature. Taking advantage of the geometry in which these liquid crystals like to arrange themselves, the researchers are able to grow compound lenses with controllable sizes.
To make the lenses, the researchers used photolithography to fashion a sheet of micropillars, then spread the liquid crystal on the sheet. At room temperature, the liquid crystal adheres to the top edges of the posts, transmitting an elastic energy cue that causes the crystal’s focal conic domains to line up in concentric circles around the posts
These lenses produce sets of images with different focal lengths, a property that could be used for three-dimensional imaging. They are also sensitive to the polarization of light, one of the qualities that are thought to help bees navigate their environments.
The compound eyes of insects can provide an extremely wide field of view due to presence of curved compound structure which is made of a collection of smaller eyes called ommatidia. Each ommatidia is made up of independent corneal lens which funnels the light onto photoreceptors through a cone. The number of ommatidia determines the resolution and varies from 180 in fire ant to 18,000 in a dragonfly.
Researchers from University of Illinois, University of Colorado Boulder and Beckman Institute have fabricated an experimental digital camera which can take wide angle photos, 160 degrees at present without distortion thus mimicking the curved compound eye of an insect eye.
This technology has potential to be utilized from micro unmanned vehicles for battlefield surveillance to endoscopy for medical diagnosis. The research was funded by the Defense Advanced Research Projects Agency and the National Science Foundation.
The scientists fabricated a 180 pixel compound eye by fabricating a layer of small microlenses connected to the second layer of stretchable silicon photodiodes through individual columns made of elastomeric polydimethylsiloxane. A third, “black matrix” layer sat on top of both the lens layer and the photodiode layer to act as the shield against background light. The lens sheet, and electronics sheet are integrated together when they are flat and later molded together into hemispherical shape that creates a near-infinite depth of field.
Octopus-Inspired Camouflage Sheet Developed By US, Chinese Research Team
Drawing inspiration from the color-changing capabilities of cephalopod skin, researchers have developed a new camouflage sheet capable of quickly reading its environment and adapting to mimic its surroundings.
The technology, known as an optoelectronic camouflage system, is based on the ability of the octopus, squid and cuttlefish to alter their appearance to hide from predators and as a way to issue warnings. In fact, in addition to changing color, the creatures can alter the shape and texture of their skin, said National Geographic’s Ed Yong. “No man-made technology comes close” to matching the transforming talents of cephalopods, Yong said.
Rogers explained that he and his colleagues are working to develop adaptive sheets that can wrap around solid objects and change their appearance – technology that could allow military vehicles to automatically camouflage themselves, or clothing that can change its color based on current lighting conditions, the National Geographic reporter added.
Lead investigators Cunjiang Yu, assistant professor of mechanical engineering at the University of Houston, and John Rogers of the Beckman Institute for Advanced Science at the University of Illinois at Urbana-Champaign have developed a prototype that currently works in black and white, with shades of gray.
However, Yu said in a statement that the technology could be enhanced to operate in the full color spectrum. The device has a flexible skin comprised of extremely thin layers of semiconductor actuators, switching components and light sensors with inorganic reflectors and organic color-changing materials that combine to allow it to autonomously color-match its background.
The three-layer design of the device was copied from the skin of the marine animals, as they have a top layer that contains the colors, a middle layer that drives the color changes, and a lower layer that senses the background patterns to be copied.
In comparison, the camouflage system is a 16-by-16 grid of squares, each of which is comprised of multiple layers, Yong explained. The top one contains heat-sensitive dye that can change color from black at room temperature to colorless at 47 degrees Celsius and back again.
The next layer is a thin piece of silver used to create a bright white background, and the one below that heats the dye and controls the color. The final layer contains a light-detector in one corner, and each of the layers above it have notches removed from their corners to allow this instrument to always view the surrounding environment. The device also possesses a flexible base, allowing it to bend and contract without breaking.
“So, the light-detectors sense any incoming light, and tell the diodes in the illuminated panels to heat up,” Yong explained. “This turns the overlying dye from black to transparent. These pixels now reflects light from their silver layer, making them look white. ”
Morpho butterfly wings inspire development of Gas sensors by GE
GE reported in Nature Communications that Nanostructures fabricated following a design of natural Morpho butterfly wings demonstrate highly selective response to gases in a variable chemical background. “These new sensors not only selectively detect separate gases but also quantify gases in mixtures, and when blended with a variable chemical background. The research team, led by Dr. Radislav Potyrailo, a Principal Scientist at Global Research’s headquarters in Niskayuna, reported its finding in the latest issue of the journal, Nature Communications.
“Material-design principles applied in nature impact many scientific fields. We found the origin of the unusually high gas selectivity of the wing scales of Morpho butterflies and fabricated a new kind of gas sensors based on these principles,” Potyrailo said.
“Our fabricated three-dimensional nanostructures not only selectively detect individual closely related vapours in pristine dry-gas conditions, similar to the natural Morpho scales and conventional sensor arrays, but also quantify these vapours even in mixtures in the presence of a variable moisture background.”
“Our design criteria for selective vapour sensing using individual photonic nanostructures involve equally important physical and chemical control. Physical control can be achieved by the nanostructure geometry and physical mechanisms of light loss in the nanostructure. Chemical control can be achieved by gradient functionalization of the whole photonic nanostructure or individual sensing lamella.”
“While quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, we achieve this goal using new individual sensors. These colorimetric sensors can be tuned for numerous gas sensing scenarios in confined areas or as individual nodes for distributed monitoring”, says Potyrailo.
“Our next goal is to make these sensors in a cost-effective manner to offer new attractive sensing solutions in the marketplace.”Potyrailo noted that the sensors can be made in very small sizes, with low production costs, enabling large volumes of them to be readily produced and deployed wherever needed.
Selective detection of vapours in the presence of a complex background is needed in medical diagnostics, environmental surveillance, homeland protection and other applications. Some Specific application requirements could include chemical surveillance in public places using unobtrusive self-contained sensor nodes of wireless sensor networks, home health care, workplace monitoring using wearable sensors, monitoring in subsea or down-hole oil and gas production, monitoring in harsh environments and others.
“GE’s bio-inspired sensing platform could dramatically increase sensitivity, speed and accuracy for detecting dangerous chemical threats,” said Radislav Potyrailo, principal investigator and a principal scientist at GE Global Research. “All of these factors are critical, not only from the standpoint of preventing exposure, but in monitoring an effective medical response if necessary to deal with such threats.”