Ultra-Flexible Single Crystal Electronics Inspired by Virus Tails

Innovation: Academia

University of Illinois Urbana-Champaign

2020

Image: CDC / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Manage Compression

When a living system is under compression, there is a force pushing on it, like a chair with a person sitting on it. When evenly applied to all sides of a living system, compression results in decreased volume. When applied on two sides, it results in deformation, such as when pushing on two sides of a balloon. This deformation can be temporary or permanent. Because living systems must retain their most efficient form, they must ensure that any deformation is temporary. Managing compression also provides an opportunity to lessen the effects of other forces. Living systems have strategies to help prevent compression or recover from it, while maintaining function. For example, African elephant adults weigh from 4,700 to 6,048 kilograms. Because they must hold all of that weight on their four feet, the tissues of their feet have features that enable compression to absorb and distribute forces.

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Fatigue

When materials that comprise living systems are subjected to repeated loads, they can weaken over time. This is called fatigue and it can lead to cracks and eventually failure. However, fatigue doesn’t occur just anywhere on a material; the cracks usually start in areas subjected to elevated local stresses. Therefore, living systems often employ shapes, materials, and/or smooth transitions to decrease the potential for fatigue. An example of using shape is found in brown algae, an intertidal seaweed. Rather than being bent by the constant flow forces of waves and currents, its shape causes it to be pulled. This reduces stress by roughly 800 times compared to another species that bends with the flow, ultimately reducing structural fatigue.

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Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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Electronic system from University of Illinois Urbana-Champaign is made of crystals that increase stretchability.

Benefits

Increased flexability

Applications

Electronics
Sensors
Medical implants

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Electronics are usually hard objects made of silicon and germanium that can break when stretched too far. This limits their applications for certain use cases, such as soft robotics and medical devices.

Innovation Details

The researchers looked for single crystal materials that could easily stretch without deforming. They found that the bacteriophage T4 virus tail is made of a single crystal of molecules. When the virus injects its DNA into bacteria, the tail is compressed over 60% of its length without deforming. They researchers mimicked this by creating an electronic system that contains an organic crystal called bis(triisopropylsilylethynyl)pentacene. This crystal can be deformed up to 10% its original length, which is ten times as much as a typical electronic crystal. Due to the crystal’s innate flexibility, the electronic system also becomes flexible.

Biological Model

The tail of the bacteriophage T4 virus is a single crystal of protein molecules. When the virus injects its DNA into bacteria, the tail is compressed over 60% of its length without losing its structural integrity.

References

Journal article

Super‐ and Ferroelastic Organic Semiconductors for Ultraflexible Single‐Crystal Electronics

Angewandte Chemie

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