An exciting new breakthrough that still needs much more
Back in May, researchers at MIT announced an awesome breakthrough: they’d figured out how to make wood in a lab. Not only could they make wood, but they could make it from cultured cells, and print it out into any shape they wanted with a 3D printer.
It’s incredible work, and the full publication is available and open source for anyone to read. But does this soon mean that we’ll have 3D printed wood, and we’ll no longer need to cut down billions of trees each year to feed our construction, furniture, and paper industries?
Short answer: no. There are still a lot of hurdles to overcome.
But it’s a promising start.
Let’s break down, simply and easily, what lead author Ashley Beckwith, PhD, and her team have done — and what challenges still persist and need to be solved.
What wood we’ve grown in the lab
Let’s quickly cover what the researchers have been able to do.
They took plant cells from a plant called Zinnia elegans, commonly known as “common zinnia.” It’s a small, flowering plant that you’ve probably seen at a flower shop.
From the leaves of these zinnia plants, the researchers extracted plant cells. These plant cells were treated with a hormone cocktail to encourage them to grow in a liquid medium.
After a couple of days, the cells were added to a nutrient-filled gel, and then extruded with a needle into specific two-dimensional patterns on a Petri dish. The Petri dishes were sealed and incubated in the dark for two months (the reasoning for the darkness was not given, but it’s likely to ensure that the plant cells only used the available nutrients instead of attempting to synthesize their own).
After two months, the dishes were opened and the prints were extracted and examined.
The goal of this experiment is to see lignification — that is, the production of a material called lignin. Lignin is a class of polymer produced by plants that provides rigidity and stability. Lignins are what give wood its strength (although it’s a negative when making paper, since it yellows over time; newspaper contains significant amounts of lignin, which is why old newspapers turn yellow).
The researchers did see lignification, which varied based on the levels of hormones added to the gel. Their grown plant material had a storage modulus (measurement of stiffness) that was similar to some soft woods. The more hormones added to the gel, the more the cells grew, but the less stiff they became. By calibrating the hormone levels, the researchers could choose the flexibility of the end product.
The result — a material that is somewhat similar to wood, created from cells from a small plant and grown into custom shapes!
So are we good? Can we now just grow and 3D print whatever wooden structures we want?
Well, not really. There are a lot of challenges still to overcome.
Where the lab-made plant material falls short
Looking at the picture from the authors’ paper above, showing the 3D printed structure, you can probably see that we’re not quite at the stage of replacing the lumber industry just yet.
Some of the challenges that we still have to solve include:
- How thick can we make the structure? In the paper, the researchers were able to grow cells in the gel matrix up to 2.5 millimeters thick. (That’s a quarter of a centimeter, or a tenth of an inch.) That’s pretty thin. They did show that they can grow these cells even with up to 9 millimeters of cell-free gel on top, suggesting that maybe this can be made up to a centimeter thick.
- Can we print in more than two dimensions? All the products in the paper are two-dimensional. The gel solution grows solid at room temperature after it’s extruded from the syringe (it’s pushed out at 52 degrees Celsius to keep it flowing), but it may not be solid enough to maintain a 3D structure.
- Can we match hardness values of natural wood? The densest printed products were only about 400 MPa in storage modulus (stiffness), while hardwoods are closer to 1,200 MPa. The lab-made product will be softer and more flexible/springy than most natural wood.
- Can we scale up? The largest lab-made structures are only a couple of inches long. This process may not scale to producing 8-foot lumber boards.
- Could this process work in a different plant species? Zinnia plants don’t naturally produce any wood-like structures. The hormone cocktail would likely need to be modified if the process was tried again with a wood-producing plant, like pine or oak.
- How much hormone products are needed to grow these? The hormone cocktail may be more expensive and less environmentally friendly to produce than just growing natural trees.
In fact, that last question may be the real sticker.
Much of the lumber that we produce these days is grown in timber forests that are planted with fast-growing trees and carefully monitored. After loggers cut down the trees, the lumber company that owns the land re-plants fresh trees.
To grow, trees pull carbon out of the air, using it as the building block to make themselves larger. When we cut down a tree and use that lumber for something stable, like building a house or a table, we’re keeping the carbon locked away, or sequestered. (That’s right — your wooden chairs are helping to keep carbon out of the atmosphere! Don’t burn them!)
On the other hand, obtaining the chemical products needed to grow cultured plant cells into lab-made wood may be a more intensive process that could result in additional carbon release. At the macro scale, lab-grown wood may be worse for the planet than traditional logging.
Lab-made wood may help combat deforestation, adding an alternative to continuing to expand the lumber forests further and further (and cutting down old-growth forests that cannot easily be regrown or replaced). But it doesn’t sound likely to replace traditional lumber any time soon — and we shouldn’t be in such a rush to eliminate this industry that pulls significant amounts of carbon out of the atmosphere.
Sum it up: lab wood is cool but not viable (yet)
It’s awesome that we’re able to show the promise of combining 3D printing, nutrient-laden gels, and extracted plant cells. The ability to grow plant cells into custom structures is fascinating, and it offers a lot of promise if we can work out how to tune the hormone cocktails to produce the structural qualities that we want.
But despite hyped-up headlines, this approach isn’t going to make the timber industry go away any time soon. So far, we’ve only been able to grow soft, wood-like structures in two dimensions, in a Petri dish (which is usually about 4 inches across). And we’ve got a lot of challenges still to solve before this begins producing any useful wood at scale.
Lab-grown wood has a long way to go, still, and we’ll also need to determine whether it’s worth replacing the carbon-sequestering approach of timber growth with lab-made products.
Still, wood made in a lab, printed on a 3D printer. A cool demonstration of our ability to culture cells!
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