The technique harnesses living cells grown in the lab from the Zinnia elegans plant and could one day be used to print all sorts of custom shapes like chairs, tables and other wood products without the need to cut down trees. .
The team was also able to fine-tune the physical and mechanical properties of the printed structures by adjusting the chemicals used in the cell growth process. This includes characteristics such as density and stiffness.
Ashley Beckwith, lead author of the study, said: ‘The idea is that you can grow these plant materials in exactly the form you need, so you don’t have to do any subtractive manufacturing after the fact, which which reduces the amount of energy and waste. There is a lot of potential to extend this and develop three-dimensional structures.
The problem of deforestation
Trees are an essential natural resource heralded for their life-saving decarbonizing effects, and we use wood for everything from buildings and furniture to paper and tools.
However, despite its relatively low cost and widespread availability, wood is not infinite, and humans are slowly but surely diminishing its supply through deforestation. To put this into context, it is estimated that the world loses around 10 million hectares of forest each year. At the current rate, many of the world’s forests could disappear over the next few centuries.
Beckwith adds: “Trees and forests are a great tool to help us manage climate change, so being as strategic as possible with these resources will be a societal necessity in the future.
A more sustainable alternative
To reduce our dependence on mother nature, researchers are now turning to alternatives to petri dishes. The MIT team began by isolating live cells from the leaves of a Zinnia elegans plant, culturing them for two days, and transferring them to gel medium where they were fed vital nutrients and two different hormones.
By adjusting hormone levels at this initial stage of growth, researchers have found that they can alter the physical and mechanical properties of plant cells as they grow. Using a 3D printer, the team then extruded the cell-laden gel material into complex structures such as the outline of a small evergreen tree. After incubation in the dark for three months and dehydration, the printed structures showed their final set of physical properties.
It has been determined that the lower the hormone exposure, the lower the plant cell density. With higher hormone levels, plant cells grew with smaller and denser cell structures, as well as more rigidity. The team even managed to achieve a stiffness comparable to that of some natural woods. As a bonus, the MIT team was able to show that the printed cell structures could survive and even continue to grow for several months after being extruded.
Luis F. Velásquez-García, co-author of the article, said, “I think the real opportunity here is to be optimal with what you use and how you use it. If you want to create an object that will serve a purpose, there are mechanical expectations to take into account. This process really lends itself to customization.
For future work, Beckwith’s team intends to investigate how genetic and chemical factors influence cell growth. They also hope to apply the bioprinting method to other plant species, including trees like pine. Ultimately, they envision a future where we could one day grow wood products in the lab with properties based on their intended applications, such as high-strength and insulating structures for building walls.
Further details of the study can be found in the article titled ‘Physical, mechanical and microstructural characterization of new plant materials, 3D printed, tunable and cultured in the laboratory, generated from cell cultures of Zinnia elegans’.
The quest for 3D wood printing
3D printing of wood and wood-like materials is not new. Last year 3D printer OEM Metal desk made headlines when it launched its subsidiary Forust, a brand focused on 3D printing functional end-use wood parts using binder jetting. The Forust process works by upgrading waste by-products from the wood and paper manufacturing industries (sawdust and lignin) and mixing them with a special bio-epoxy resin composite that can be printed on.
Elsewhere, an alternative wood substitute made from kombucha tea waste received last year’s national award James Dyson Award. Pyrus, a 3D printable wood-like material made from bacterial cellulose grown on top of kombucha tea while it is steeped, was developed by University of Illinois student Gabe Tavas. Since then, he has been trying to increase the production of his material.
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Featured image shows microscopic images of cultured Zinnia plant cells prior to 3D printing. Image via MIT.