Vascularised composites could lead to self-healing materials

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Illinois University researchers have developed vascularised structural composites, creating materials that are lightweight and strong with potential for self-healing or self-cooling.

‘We can make a material now that’s truly multifunctional by simply circulating fluids that do different things within the same material system,’ said Scott White, the Willett professor of aerospace engineering who led the group. ‘We have a vascularised structural material that can do almost anything.’

The Illinois team, part of the Autonomous Materials Systems Laboratory in the Beckman Institute for Advanced Science and Technology, developed a method of making fibre-reinforced composites with tiny channels for liquid or gas transport.

The key to the method, published in the journal Advanced Materials, is said to be the use of so-called sacrificial fibres.

The team treated commercially available fibres so that they would degrade at high temperatures. The sacrificial fibres are no different from normal fibres during weaving and composite fabrication. But when the temperature is raised further, the treated fibres vaporise — leaving tiny channels in their place — without affecting the structural composite material itself.

‘There have been vascular materials fabricated previously, including things that we’ve done, but this paper demonstrated that you can approach the manufacturing with a concept that is vastly superior in terms of scalability and commercial viability,’ said White.

In the paper, the researchers demonstrated four classes of application by circulating different fluids through a vascular composite: temperature regulation, chemistry, conductivity and electromagnetism.

They regulated temperature by circulating coolant or a hot fluid.

To demonstrate a chemical reaction, they injected chemicals into different vascular branches that merged, mixing the chemicals to produce a luminescent reaction.

They made the structure electrically active by using conductive liquid and changed its electromagnetic signature with ferrofluids, which is said to be a key property for stealth applications.

Next, the researchers hope to develop interconnected networks with membranes between neighbouring channels to control transport between channels. Such networks would enable many chemical and energy applications, such as self-healing polymers or fuel cells.

‘This is not just another microfluidic device,’ said co-author Nancy Sottos, the Willett professor of materials science and engineering and a professor of aerospace engineering. ‘It’s not just a widget on a chip. It’s a structural material that’s capable of many functions that mimic biological systems. That’s a big jump.’

The work was supported by the US Air Force Office of Scientific Research.