Self-healing materials to shape the cars of the future
Ben Smye explores current trends in self-healing materials research, and where they could lead the automotive industry in the years to come
It sounds like something out of a sci-fi movie, but the idea of ââa self-healing car might not be as wild and futuristic as it sounds. While machines that can repair themselves are a long way off, materials engineers have developed technology that may soon make this fiction a reality.
How do self-healing materials work?
The best known way to create a material that can heal is to incorporate small capsules of healing agent inside the material itself. When the material is damaged, the capsules shatter and release the repair substance. However, the size of the capsules is crucial in this design, because if they are too large, the material will be weakened. They can also only be used once, which is not ideal if a material is susceptible to repeated damage.
However, engineers have created self-healing materials that work through vascular networks, similar to veins on a leaf. In these microvascular materials, when there is a crack, the healing agent travels through the vascular network and heals the rupture. This has been shown to be effective, but it is also a slower method of repairing a material.
One challenge when creating self-healing materials that can be used in the automotive industry is that it is much more difficult to create metals with these properties. Many vehicle parts are made of metal, but due to the chemical construction of metals and the way their atoms bond together, it is difficult to create a self-healing metal. As a result, design engineers often focus their research on polymers.
Cars that never get scratched or can repair their own damage could roll on the roads for decades to come
Research on self-healing polymers has yielded groundbreaking results. It is now possible to have an intelligent polymer that can regain its previous characteristics even after being damaged. Even more exciting, materials scientists were able to develop smart polymers called intrinsic polymers that can repair themselves without external stimuli. These intrinsic polymers have specific reversible chemical bonds, which means that they can return to their original properties.
All of these developments are promising, but the question remains how these early steps in self-healing materials can be more than mere curiosities from a lab. Many researchers are therefore exploring the practical applications of their developments. For example, researchers are studying the potential of self-healing polymeric coatings in the context of space exploration and the high seas. In these situations, a coating would greatly reduce maintenance costs, as these are difficult places for repair work.
These coatings are designed for extreme environments, but if successful in these areas, products will likely be available in other areas. Some of the coatings being designed are anticorrosive, while others are scratch resistant. These features are obviously useful for traveling in space and under the sea, but they would also be beneficial for vehicles that operate in less extreme conditions.
The painting of cars is one of the main reasons for the increase in costs during car maintenance. If developments in self-healing polymer coatings can create a paint capable of withstanding minor scratches and corrosion, this could impact the amount auto operators have to spend on repairs. Even something this simple has the potential to extend vehicle life, which would be good news for users.
Reversible chemical bonds are also at the heart of another technological breakthrough. Researchers from Harvard University has developed a strong, self-healing rubber. To do this, they combined covalent and reversible bonds to create a molecular string. The result is a transparent rubber that heals by distributing the stresses around the material.
When rubber cracks, it is usually because the stress has localized at some point. The molecular makeup of self-healing rubber prevents this from happening, as the material distributes stress through a network of cracks, which are essentially cracks connected by fibrous strands. By allowing the stress to be dispersed more evenly throughout the substance, the self-healing rubber is much more able to cope with the force applied to it.
Self-healing rubber has many potential practical applications. It could be used to make rubber bands that never break, but the main use that researchers have highlighted is in tires. Tires made with this type of rubber would be able to withstand more stress than those currently available and would likely last longer, even in extreme environments. It has even been suggested that if a tire were to be cut, if it was made of self-healing rubber, it would not need to be replaced immediately.
It sounds like something out of a sci-fi movie, but the idea of ââa self-healing car might not be as wild and futuristic as it sounds
But maybe we need to look beyond the cars themselves to the uses of self-healing materials. Road pavements are easy to overlook when thinking about improvements in materials science. However, recent developments mean that in addition to cars with self-healing properties, roads could also display these characteristics in the future.
In a promising development, scientists have patented a self-healing concrete. Hendrik Marius Jonkers concrete contains bacteria that produce lime, allowing the road surface to repair itself. The roads of the future thus have the potential to fill their own potholes. Pothole repair cost the UK around Â£ 1.3bn (US $ 1.84bn) in 2020, so developing a self-healing road could do more than just render smoother driving experience; this could reduce repair costs and potentially extend vehicle life.
In the area of ââself-healing materials, it looks like science is doing its best to catch up with fiction. However, it is not there yet. Until then, design engineers must work to select the materials best suited to the requirements of their project. Design engineers need simple ways to research and compare various materials in order to choose the one that performs best, and material databases like Matmatch can help.
For example, a polyamide material such as ForTii 11 provides optimum toughness for automotive electrical components. This high temperature polyamide contains halogen free and halogen containing flame retardants and works well in harsh environments. It minimizes the risk of cracking, and improves the reliability of the product in terms of aging by thermal shock.
Futuristic cars that can self-repair may not yet be available for purchase, but research into self-healing materials is gaining ground every year. Cars that never get scratched or can repair their own damage could roll onto the roads for decades to come. Although the technology is still under development, scientists and materials engineers are turning science fiction into scientific facts.
About the Author: Ben Smye is Head of Growth at Matmatch material search engine