Recent research at the Massachusetts Institute of Technology (MIT) has found a method for using cellulose, the most abundant organic polymer in the world, as the feedstock for 3-D printing and additive manufacturing processes, according to a report on the school’s website.
This image from a scanning electron microscope shows a cross section of an object printed using cellulose.
The inset shows the surface of the object. (MIT)
There have been previous attempts at using cellulose in 3-D printing but it thermally decomposes before flowing because of the hydrogen bonds between cellulose molecules. Also, the bonding between molecules means that solutions with a high concentration of cellulose are “too viscous to extrude”.
To avoid those issues, MIT researchers used the widely available material cellulose acetate, which has fewer hydrogen bonds than cellulose because of the introduction of acetate.
The article explained, “Cellulose acetate can be dissolved in acetone and extruded through a nozzle. As the acetone quickly evaporates, the cellulose acetate solidifies in place. A subsequent optional treatment replaces the acetate groups and increases the strength of the printed parts.”
The hydrogen bonds are restored after printing with a sodium hydroxide treatment and the researchers found that this process created stronger and tougher parts than with standard 3-D printing materials acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). They also demonstrated that the material could be tuned, such as adding anti-microbial dye to produce parts with anti-microbial properties.
“Because most existing extrusion-based 3-D printers rely on heating polymer to make it flow, their production speed is limited by the amount of heat that can be delivered to the polymer without damaging it,” the article continued. “This room-temperature cellulose process, which simply relies on evaporation of the acetone to solidify the part, could potentially be faster.”
Cellulose acetate is widely available in bulk and, coupled with the room temperature technique described by the MIT researchers, could prove a cost-effective alternative to the filament materials commonly used in 3-D printing processes.
The research was recently published in Advanced Materials Technologies. The abstract stated:
“Additive manufacturing of pure cellulosic objects is demonstrated via extrusion of cellulose acetate and conversion to cellulose, rendering parts with isotropic strength and high toughness. Ease of functionalization is shown by addition of antimicrobial dye to the printing ink, which kills 95% of bacteria upon exposure to light.”