A vascularized fiber-reinforced composite material. Illinois researchers developed a class of sacrificial fibers that degrade after composite fabrication, leaving hollow vascular tunnels that can transport liquids or gases through the composite. Image: Piyush Thakre, Alex Jerez, Ryan Durdle and Jeremy Miller, Beckman Institute, U. of I. |
Taking their cue from biological circulatory systems, University of Illinois researchers have developed
vascularized structural composites, creating materials that are lightweight and
strong with potential for self-healing, self-cooling, metamaterials, and more.
“We can make a material now that’s truly multifunctional by
simply circulating fluids that do different things within the same material
system,” says Scott White, the Willet Professor of aerospace engineering who
led the group. “We have a vascularized structural material that can do almost
anything.”
Composite materials are a combination of two or more
materials that harness the properties of both. Composites are valued as
structural materials because they can be lightweight and strong. Many
composites are fiber-reinforced, made of a network of woven fibers embedded in
resin—for example, graphite, fiberglass, or Kevlar.
The Illinois
team, part of the Autonomous Materials Systems Laboratory in the Beckman
Institute for Advanced Science and Technology, developed a method of making
fiber-reinforced composites with tiny channels for liquid or gas transport. The
channels could wind through the material in one long line or branch out to form
a network of capillaries, much like the vascular network in a tree.
“Trees are incredible structural materials, but they’re
dynamic too,” says coauthor Jeffrey Moore, the Murchison-Mallory professor of chemistry
and a professor of materials science and engineering. “They can pump fluids,
transfer mass and energy from the roots to the leaves. This is the first step
to making synthetic materials that have that kind of functionality.”
The key to the method, published in Advanced Materials, is the use of sacrificial fibers. The team
treated commercially available fibers so that they would degrade at high
temperatures. The sacrificial fibers are no different from normal fibers during
weaving and composite fabrication. But when the temperature is raised further,
the treated fibers vaporize—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,” White says.
In the paper, the researchers demonstrate four classes of
application by circulating different fluids through a vascular composite:
temperature regulation, chemistry, conductivity, and electromagnetism. They
regulate 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—a key property for stealth
applications.
Next, the researchers hope to develop interconnected
networks with membranes between neighboring 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,” says coauthor
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.”
