Imagine making something thinner than a piece of hair that is stronger than steel! Nanomaterials are a broad grouping in materials science that describes very tiny materials. These tiny materials can have amazing properties. One example of these very tiny materials with extraordinary properties is a kevlar nanomaterial that is stronger than steel. This kevlar nanomaterial is a nanoribbon with a structure similar to a cell membrane and chemistry similar to an aramid. A group of researchers at the Massachusetts Institute of Technology led by Dr. Julia Ortny developed a self-assembled nanoribbon that is structurally similar to a cell membrane and chemically similar to Kevlar. And if that is confusing now, don’t worry, stay with me. We are going to break it all down.
What Are Nanomaterials?
So first, let’s refresh on nanomaterials. Nanomaterials are shapes and structures that some or all of their dimensions are 10-9 meters, and for context, a strand of hair is about 10-20 micrometers in diameter, which is 10-6. This makes a single strand of hair is 1000 larger than a nanomaterial. These strong materials we are talking about today are 1000 times smaller than the diameter of a single strand of hair.
What is Self-Assembly?
Self-assembly is a phenomenon that occurs when materials or objects can spontaneously generate order within a system. From individual shapes spontaneously forming patterns to a material’s components forming together to make a long nanosized chain called a nanoribbon.
Structure of the Nanoribbons
The researchers designed biologically inspired nanoribbons. The nanoribbons’ structure mimics the walls of cells. In biology classes, the cell membrane is called the lipid bilayer. Specifically, the cell membrane is made up of many tiny molecules that join themselves together in regards to the structure. These tiny molecules can join together to make the cell membrane because they have two parts. The outer layer is hydrophilic, which means it loves water and molecules similar to water or can be dissolved in water. Then the inner part is hydrophobic, which means it repels water and prefers molecules that do the same. Like magnets, their hydrophilic heads are attracted to other hydrophilic heads and repelled by the hydrophobic tails, and the opposite is true for the hydrophobic tails.
Challenges with the Nanoribbons
Dr. Ortnys’ team took inspiration from the cell wall structure and created tiny polymers with the same hydrophilic head and hydrophobic tail orientation. This style of strong nanoribbons has been made in the past. However, when they are dried after being formed, other nanoribbons often lose that strength and shape. Because they are not surrounded by water to maintain that same hydrophilic out hydrophobic in orientation. But if you think about the real world, if we want to use the strong threads for things like clothing or manufacturing, they have to be used wet and dry.
Strengthening the Nanoribbons
To solve this problem, Dr. Ortnys’ team took inspiration from a widely used material known for its strength, Kevlar. If you aren’t familiar with Kevlar’s name, you are probably familiar with one of its most common applications, body armor.
History of Kevlar
Kevlar is a synthetic polymeric material that Dupont developed in the 1960s by a female chemist named Stephanie Kwolek. It is known for being very strong and heat resistant, so it is commonly used for body armor. Kevlar belongs to a family of materials called aramids. They got this name because the polymer is made by binding a bunch of smaller molecules or monomers together with an amide bond resistant to heat and many harsh chemicals.
The strong amide bond that makes Kevlar and other popular aramids like Nomex strong and heat resistant is the same type of bond that Dr. Ortny’s group used to stabilize the hydrophobic tails cell membrane-like nanoribbons in and out of water. Once the nanoribbons were stabilized in and outside of water, they could dehydrate them and then pull them to make a long thread.
Applications for Kevlar Nanoribbons
They have used these threads to make filters with additional molecules. One of the first applications they tried was to filter heavy metals out of water. Filtration systems can be costly, so these very durable filters can be made as a potential replacement. Due to these nanoribbons’ strength, I am sure that many additional applications are discovered for them.