Biocompatible Lenses Inspired by Spider Silk

Innovation: Academia

Tamkang University

2020

Image: Hans / Pixabay / CC BY - Creative Commons Attribution alone

Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Modify Material Characteristics

The materials found in living systems are variable, yet often made from the same basic building blocks. For example, all insect exoskeletons consist of a material called chitin. Because material resources are limited, each material within or used by a given living system must frequently serve multiple purposes. Therefore, living systems have strategies to modify materials’ softness, flexibility, and other characteristics. To ensure survival, the benefits of these modifications must outweigh the living system’s energy and material expenditure to generate them. For example, spiders store the liquid components of spider silk in a gland, converting them into silk thread when needed. Some threads have different characteristics, such as elasticity and UV reflectance, than others.

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Dome lens from Tamkang University utilizes the properties of spider silk to form a dome shape out of resin.

Benefits

Improved efficiency
Biocompatible
Versatile

Applications

Medical imaging
Medical implants

UN Sustainable Development Goals Addressed

Goal 3: Good Health & Wellbeing
Goal 12: Responsible Production & Consumption

Bioutilization

Spider silk

The Challenge

Medical imaging needs to be high resolution at very small scales, which requires specialized lenses. These lenses are oftentimes composed of intricate shapes, resulting in a higher error rate during manufacturing. This also makes them more expensive and difficult to manufacture.

Innovation Details

Spider silk exhibits many impressive properties, including high elasticity and tensile strength, while still being biocompatible. This makes it superior to current synthetic fibers. The lens is made using dragline silk collected from daddy longlegs spiders. Resin is dripped onto the fiber, and as the resin condenses it causes the silk to form into a dome shape, which can be used as an optical lens.

When a laser is shined onto the lens, it generates a high-quality photonic nanojet, which is a type of beam that can provide large-area, super-resolution imaging for biomedical applications. The size of the dome lens can be altered for different types of imaging by altering the time the silk is suspended in the resin.

Biological Model

Spider silk contains properties that allow water to stick to it and condense, helping the spider to harvest water when it’s thirsty. To maximize the amount of water that gets trapped in its web, spiders use a comb-like structure on their legs to puff up their silk into a ball-like tangle. They then weave webs that alternate these tangles with straight, smooth, thin sections of silk threads, making a kind of beaded necklace structure. When water condenses on the web it starts to move, migrating from the thin threads towards the tangles, where it gets stuck because the tangled parts of the web have more area for the water to stick to.

See Related Strategy

Biological Strategy

Web Continuously Collects Water From Air

The structure of special silk from cribellate spiders continuously pulls and transports water from the air.

References

Journal article

Optimal photonic nanojet beam shaping by mesoscale dielectric dome lens

Journal of Applied Physics

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