Implantable Composite Material Inspired by Silkworm Silk

Innovation: Academia

Beihang University

2020

Image: Butterflyarc / Pixabay / CC BY SA - Creative Commons Attribution + ShareAlike

Manage Tension

When a living system is under tension, it means there is a force pulling on it, like a person pulling on a rope tied to a horse. When applied to a living system, unless the system is completely rigid, the result is that it gets stretched. If stretching exceeds the strength of the living system’s material, it can damage it. Living systems manage tension using materials that are flexible and stretchable enough to survive most tension that occurs in their environment. The ocean’s intertidal zone offers a good example. The waves and incoming and outgoing tides put tension on soft-bodied organisms. Mussels resist tension with flexible threads that hold them onto rocks; in contrast, large algae have stretchy fronds.

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Manage Mechanical Wear

A living system is subject to mechanical wear when two parts rub against each other or when the living system comes in contact with abrasive components in its environment, such as sand or coral. Some abrasive components are a constant force, such as finger joints moving, while others occur infrequently, such as a sand storm moving across a desert. Living systems protect from mechanical wear using strategies appropriate to the level and frequency of the source, such as having abrasion-resistant surfaces, replaceable parts, or lubricants. For example, human joints like shoulders and knees move against each other all day, every day. To protect from mechanical wear, a lubricant reduces friction between the cartilage and the joint.

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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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Robust biomaterial from Beihang University uses a mixture of silkworm silk and a polymer matrix to create a durable, biocompatible material.

Benefits

Biocompatible
Increased efficiency
Durable
Versatile

Applications

Medical implants
Composite materials
Manufacturing

UN Sustainable Development Goals Addressed

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

Bioutilization

Silkworm silk

The Challenge

Many people need surgical implants throughout their lifetime for a variety of medical reasons. Each time a foreign material is implanted into the human body, it risks incompatibility and rejection. Furthermore, many materials can become uncomfortable, causing irritation over time that can lead to further complications.

Innovation Details

The composite material is made from silkworm silk and a matrix such as epoxy. This mixture creates a laminate material with inherent biocompatibility. The silk’s long fibers are able to more evenly distribute mechanical stresses throughout the durable epoxy. The material can be cut and formed into different shapes and sizes.

Biological Model

Silkworm silk is made of stretchable fibers approximately 5,000 feet long. Having a single, long fiber enables the material to more effectively distribute mechanical stress than several shorter, individual ones.

References

Book

Silk Lattice Structures from Unidirectional Silk Fiber–Reinforced Composites for Breaking Energy Absorption

Advanced Engineering Materials

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