Self-Assembling Composite Inspired by Squid Ring Teeth Proteins

Innovation: Academia

Penn State

2020

Image: Klaus Stiefel / Flickr / CC BY NC - Creative Commons Attribution + Noncommercial

Store Energy

Once a living system captures energy or transforms one energy form into another, it must frequently save that energy for future use. But energy is difficult to store in some forms. So living systems need strategies to either use energy quickly, or to convert it from forms that are difficult to store (such as electrical or kinetic) to more storable forms. For example, grasshoppers store energy as potential energy in an elastic material in their tendons. When they need to jump, that energy converts into kinetic energy, providing the force needed to escape predators.

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Chemically Assemble Polymers

We might think that complex polymers are the result of human industrial ingenuity, but nature cornered the market on polymers billions of years earlier. Examples of biopolymers are proteins, carbohydrates, and genetic material. In contrast to human industrial processes, within a cell, ribosomes covalently bond amino acids together to form proteins.

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Composite material from Penn State University has tunable electric properties due to bioengineered tandem repeat proteins.

Benefits

Flexible
Conductive
Controllable

Applications

Electronic devices

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Composite materials have limited physical properties due to the physical limits of the components and interactions between them. The ‘rule of mixtures’ is a prediction theory that states that while the matrix-to-filler ratios of one component to another can vary in a mixture, there is a limit to the physical properties (elastic modulus, tensile strength, etc.) of the composite. This has prevented material scientists from creating mixtures with tunable properties.

Innovation Details

The composite material is made of a synthetic tandem repeat inspired by the structure of squid ring teeth proteins, and a very thin metal known as titanium carbide 2D MXene. The composite self-assembles into a cross-linked network, which changes the electrical properties of the layered material and causes the matrix-to-filler ratios in tiny areas to ‘break’ the mixture rules. On the microscopic scale, when the structural symmetry is broken, electrical conductivity depends on direction. As long as the current is going along the plane of the 2D material layers, the conductivity is linear, but if the current is directed across the layers, the conductivity becomes nonlinear. This allows the researchers to make different types of electronic devices, such as storage devices, diodes, switches, or regulators. The researchers can control the distance between conducting layers without changing the composite fraction by controlling the length of the tandem repeat proteins, which they have bioengineered.

Biological Model

Squid have teeth in ring formations inside suction cups on their tentacles. The squid ring teeth are made up of proteins that can combine in different ways to produce materials with different properties. These teeth help the squid grip onto a surface or grasp prey. If the teeth break, they can self-heal.

See related strategy on how squid capture prey

Biological Strategy

Composites Provide Strength

Humboldt squid

The beaks of jumbo squid are flexible near the body and stiff near the tip, as defined by varying degrees of water content in a composite of chitin nanofibrils infused with cross-linked proteins.

References

Journal article

Self-Assembly of Topologically Networked Protein–Ti3C2Tx MXene Composites

ACS Publications

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