From wood flour to 3D objects and shapes
Researchers from The Hebrew University of Jerusalem have investigated and worked on turning flat, wooden shapes ejected by 3D printing into programmed, self-morphing 3D shapes using what they call ‘wood flour.’ The powder comprises wood-waste microparticles mixed with nanocrystals and xyloglucan, which are natural binders extracted from plants, and the researchers developed a water-based ink from the mixture during and for their studies.
For the research, they used the ink mixture in a 3D printer and discovered that the way the ink is laid down governs the morphing behavior of the wood as the moisture from the mixture evaporates from the printed piece. The researchers believe this technique could be used to make furniture such as wooden chairs or other wooden products that can be used for architecture and as decorations. They could be shipped flat to a destination before drying them to form the desired, final shape.
screenshots courtesy of American Chemical Society | header image by Doron Kam
Stimuli affect the 3D-printed flat sheets
Eran Sharon, Ph.D., one of the project’s principal investigators, says that unlike the objects found in nature, artificial structures cannot typically shape themselves without manual labor, but scientists have begun printing flat sheets that could form themselves into 3D shapes using a stimulus, such as a change in temperature, pH, or moisture content. But these self-morphing sheets were made from synthetic materials, such as gels and elastomers, as Sharon notes.
He and his team from The Hebrew University of Jerusalem – which includes Doron Kam, Shlomo Magdassi, Ph.D., Oded Shoseyov, Ph.D., and Ido Levin, Ph.D. – circled back to the origin of the concept which was wood. During their research, they printed a flat disk as a series of concentric circles and it dried and shrunk to form a saddle-like structure reminiscent of a potato chip. The team is also exploring whether the morphing process could be made reversible. ‘We hope to show that under some conditions we can make these elements responsive — to humidity, for example — when we want to change the shape of an object again,’ says Sharon.
DNA-shaped self-morphing object
Shapes can be controlled by adjusting print speed
So far, the researchers have discovered that the ultimate shape of the object can also be controlled by adjusting print speed since shrinkage occurs to the wood fibers in the ink and print speed changes the degree of alignment of those fibers. They note that a slower rate leaves the particles more randomly oriented and faster printing aligns the fibers with one another, so shrinkage is more directional.
The scientists also learned how to program the print speed and pathway to achieve a variety of final shapes and found that piling up two rectangular layers that are printed in different orientations creates a helix after drying. In their latest work, they found that they can program the printing pathway, speed, and stacking to control the specific direction of shape change, such as whether rectangles twist into a helix that spirals clockwise or counterclockwise.
flat wood sheet after printing
potato chip-shaped flat sheet after drying