Your next wooden chair could arrive flat and then dry into a 3D shape.

Your next wooden chair could arrive flat and then dry into a 3D shape (video)

The wood ink printed as a flat rectangle is programmed to form a complex shape after drying and solidifying. (The ruler is marked in centimeters.) Credit: Doron Kam

Wooden objects are usually made by sawing, carving, bending, or pressing. That’s so old school! Today, scientists will describe how flat shapes of wood extruded by a 3D printer can be programmed to transform into complex 3D shapes. In the future, this technique could be used to make furniture or other wood products that could be shipped flat to a destination and then dried to the desired final shape.

The researchers will present their results at the fall meeting of the American Chemical Society (ACS).

In nature, plants and some animals can alter their own shapes or textures. Even after a tree is cut down, its wood can change shape as it dries. It shrinks unevenly and warps due to variations in the orientation of the fibers within the wood. “Deformation can be a hindrance,” says Doron Kam, a graduate student presenting the work at the meeting, “but we thought we could try to understand this phenomenon and turn it into a desirable transformation.”

Unlike some natural objects, man-made structures typically can’t mold themselves, says Eran Sharon, Ph.D., one of the project’s principal investigators. But in recent years, scientists have started printing flat sheets that could take on three-dimensional shapes after a stimulus, such as a change in temperature, pH, or moisture content, says Sharon. However, these self-transforming sheets were made of synthetic materials, such as gels and elastomers, he notes.

“We wanted to go back to the origin of this concept, to nature, and make it out of wood,” says Sharon. He and Kam, as well as Shlomo Magdassi, Ph.D., and Oded Shoseyov, Ph.D., the other principal investigators who took on this challenge with Ido Levin, Ph.D., who was a graduate student at the time. —They are at the Hebrew University of Jerusalem.

A few years ago, the team developed an environmentally friendly water-based ink made up of microparticles of wood waste known as “wood flour” mixed with nanocrystals of cellulose and xyloglucan, which are natural binders extracted from plants. The researchers then began using the ink in a 3D printer. They recently discovered that the way the ink is deposited, or the “path,” dictates the transformation behavior as the moisture content evaporates from the printed part. For example, a flat disk printed as a series of concentric circles dries and shrinks to form a saddle-like structure reminiscent of a Pringles potato chip, and a disk printed as a series of rays emanating from a point central becomes a dome or cone. -similar structure.

The final shape of the object can also be controlled by adjusting the print speed, the team found. This is because shrinkage occurs perpendicular to the wood fibers in the ink, and print speed changes the degree of alignment of those fibers. A slower speed leaves the particles more randomly oriented, so shrinkage occurs in all directions. Faster printing aligns the fibers with each other, so shrinkage is more directional.

Scientists learned to program the print speed and path to achieve a variety of final shapes. They found that stacking two rectangular layers that are printed in different orientations produces a helix after drying. In their latest work, they found they can program the print path, speed, and stacking to control the specific direction of the shape change, like whether the rectangles are twisted into a clockwise or counterclockwise helix.

Further refinement will allow the team to combine mounts, domes, propellers, and other design motifs to produce objects with complicated final shapes, such as a chair. Ultimately, it might be possible to make wood products that ship flat to the end user, potentially reducing shipping volume and costs, says Kam. “Then at the destination, the object could be deformed into the structure you want.” Eventually, it might be feasible to license the technology for home use so that consumers can design and print their own wooden objects with a regular 3D printer, says Sharon.

The team is also exploring whether the transformation process could be made reversible. “We hope to show that under some conditions we can make these elements respond, for example to moisture, when we want to change the shape of an object again,” says Sharon.

Essential 3-D morphing

More information:
Wood Warping Using 3D Printing, ACS Fall 2022.…tings/fall-2022.html

Provided by the American Chemical Society

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