MIT technique produces nanofibres with exceptional strength and resilience

Researchers at MIT have developed a process, called gel electrospinning, that can produce ultrafine fibres that are exceptionally strong and tough. These fibres, which should be inexpensive and easy to produce, could be used in applications such as armour and nanocomposites.

Typically, researchers enhancing one characteristic of a material will see a decline in a different characteristic. Professor of chemical engineering Gregory Rutledge explained: “Usually when you get high strength, you lose something in the toughness. The material becomes more brittle and therefore doesn’t have the mechanism for absorbing energy, and it tends to break.”

But in the fibres made by prof Rutledge’s process, many of those trade-offs are eliminated. Using a variation of gel spinning that adds electrical forces results in ultrafine fibres of polyethylene that match or exceed the properties of some of the strongest fibre materials, such as Kevlar and Dyneema.

“We started off with a mission to make fibres below 1 micron, because those have a variety of interesting features in their own right,” prof Rutledge said. “There hasn’t been a whole lot new happening in that field in many years, because they have very top-performing fibres in that mechanical space.” But this new material, he says, exceeds all the others. “What really sets those apart is what we call specific modulus and specific strength, which means that on a per-weight basis they outperform just about everything.”

Compared to carbon fibres and ceramic fibres, which are widely used in composite materials, the new gel-electrospun polyethylene fibres have similar degrees of strength but are much tougher and have lower density.

In creating this ultrafine material, the team had aimed to match the properties of existing microfibers. However, the material turned out to be better in significant ways. Crucially, he said: “The strengths are about a factor of two better than the commercial materials and comparable to the best available academic materials, and their toughness is about an order of magnitude better.”

The researchers are still investigating what accounts for this impressive performance. Prof Rutledge explained that “most plastics are tough, but they’re not as stiff and strong as what we’re getting.”

These results might lead to protective materials that are as strong as existing ones but less bulky, making them more practical. And, prof Rutledge added: “They may have applications we haven’t thought about yet, because we’ve just now learned that they have this level of toughness.”

Author
Tom Austin-Morgan

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