Aimed at providing an environmentally friendly and low-waste alternative to forestry, researchers at the Massachusetts Institute of Technology (MIT) pioneered the tuneable technique to generate wood-like plant material in a lab. The process could enable a manufacturer to ‘grow’ a wooden product such as a table without needing to cut down trees or process lumber, the researchers said.
By adjusting certain chemicals during the growth process, the researchers said they can precisely control the physical and mechanical properties of the resulting material, such as stiffness and density.
Using 3D bioprinting techniques, they can also grow plant material in shapes, sizes, and forms that are not found in nature, and which cannot easily be produced using traditional agricultural methods.
“The idea is that you can grow these plant materials in exactly the shape that you need, so you don’t need to do any subtractive manufacturing after the fact, which reduces the amount of energy and waste,” said Ashley Beckwith, lead author of a paper on the work. “There is a lot of potential to expand this and grow three-dimensional structures.”
Desirable properties for lab-grown materials could include high strength for housebuilding, said senior author Luis Fernando Velásquez-García from MIT’s Microsystems Technology Laboratories, or certain thermal properties for efficient heating of internal spaces.
To begin the process, the researchers first isolated cells from the leaves of young Zinnia elegans plants. The cells were cultured in liquid medium for two days, then transferred to a gel-based medium, which contains nutrients and two different hormones.
Adjusting the hormone levels at this stage enabled researchers to tune the physical and mechanical properties of the plant cells that grow.
“In the human body, you have hormones that determine how your cells develop and how certain traits emerge. In the same way, by changing the hormone concentrations in the nutrient broth, the plant cells respond differently. Just by manipulating these tiny chemical quantities, we can elicit pretty dramatic changes, in terms of the physical outcomes,” Beckwith said.
The team used a 3D printer to extrude the cell culture gel solution into a specific structure in a petri dish, and let it incubate in the dark for three months. Following incubation, the resulting material was dehydrated and evaluated.
Even with the incubation period, the process is about two orders of magnitude faster than the time it takes for a tree to grow to maturity, Velásquez-García said.
Using a 3D bioprinting process, the researchers also demonstrated that the plant material can be grown into custom shapes and sizes. The process uses a CAD file fed into the bioprinter, which deposits the cell gel culture into specific shapes, such as a tiny model of an evergreen tree.
The cell cultures could survive and continue to grow for months after printing, the researchers said, and using a thicker gel did not impact the survival rate of the lab-grown cells.
“I think the real opportunity here is to be optimal with what you use and how you use it,” said Velásquez-García. “If you want to create an object that is going to serve some purpose, there are mechanical expectations to consider. This process is really amenable to customisation.”
The team will continue experimenting to better understand and control cellular development. They also hope to evaluate if the method could be transferred to other species of plant.
The research was published in Materials Today.
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