MAKING THERMAL INSULATION WITH STRAW
Researchers from SUNY Buffalo are the first to 3D print insulation structures using wheat straw fibers.
Written by Kayt Sukel
IN THE CLASSIC ENGLISH FOLKTALE, “The Three Little Pigs,“ the first pig builds his house of straw—and immediately regrets it when the Big Bad Wolf easily blows the structure down. While straw on its own is not necessarily the most resilient building material, it has been used for centuries to fortify mud bricks, as well as being used as a roofing material. Settlers in the 1800s even used straw bales from their farms to create insulated, load-bearing walls in Nebraska homes. And today, there is a resurging interest in straw bale construction thanks to the material being both sustainable and cost-effective to use.
Chi Zhou, associate professor in the State University of New York (SUNY) Buffalo’s Department of Industrial and Systems Engineering, said he became interested in the use of straw for insulation purposes after working on an additive manufacturing project to produce silica aerogel-based materials. Like other common forms of building insulation, this material had good mechanical properties, but it is not environmentally friendly.
“We started to think about using a material for insulation that is biodegradable. Straw fibers have been used for centuries,” he explained. “We thought that it could be a good substitute to replace silicon, as well as the fiberglass, wool, foam, and other traditional materials that are used in insulation because wheat straw is reusable, cheap, and readily available.”
“Straw fibers have been used for centuries. We thought that it could be a good substitute to replace silicon, as well as the fiberglass, wool, foam, and other traditional materials that are used in insulation because wheat straw is reusable, cheap, and readily available.”
—Chi Zhou, associate professor in the State University of New York (SUNY) Buffalo
Zhou and colleagues decided to pursue an additive manufacturing approach to process straw fiber and combine it with silica aerogel to produce a new material with both strong thermal insulation and mechanical properties. As they looked to create this composite material for building applications, it was challenging to balance all the objectives they hoped to achieve, he said.
“We had multiple goals for the material, and they all conflicted with one another. We want a solution that has the right properties—but it has to have the right cost and be environmentally friendly,” Zhou continued. “We also have to make sure that the material we come up with is manufacturable.”
The team developed a novel formulation of a 3D printable ink made up of chopped wheat straw fibers. By leveraging a direct ink writing process, the researchers were able to deposit the straw fibers into 3D structures. When they tested the material, they were able to demonstrate it had strong insulative properties (i.e., low thermal conductivity) and maintained the mechanical strength similar to that of silica aerogel on its own. Zhou was surprised at how well it worked.
“It turns out it the cost is quite acceptable, and the performance is quite outstanding,” he said.
The biodegradable fiber that Chi Zhou's team has developed offers multiple environmental advantages over fiberglass, the current industry standard. Photo: State University of New York Buffalo
The team now plans to work out how to manufacture this new material at scale. Most insulated drywall panels are four feet by eight feet. Currently, the team has developed a prototype panel that is approximately one foot by one foot.
“We are looking at how to build this into an industrial panel and make sure that our material is compatible with existing manufacturing machines,” he said. “Then we can put this into large production.”
But, in the meantime, Zhou said he hopes that other engineers recognize the power of additive manufacturing and 3D printing for a wide range of base materials.
“These methods provide a lot of new pathways for existing materials like wheat straw fibers and more,” he said. “It is very flexible. You can use it to print ceramic, plastic, metal, and other things—but no one thought to use 3D printing for straw fiber. So, if any material can be processed traditionally, there’s a chance you can also use 3D printing with it to create new and interesting applications.”
Kayt Sukel is a technology writer and author in Houston.
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