Mar 6, 2017 | By Benedict

Researchers at MIT have developed a technique for 3D printing with cellulose acetate, a cellulose material with a reduced number of hydrogen bonds. Unlike other forms of cellulose, cellulose acetate can be dissolved in acetone and extruded through the nozzle of a 3D printer.

Cross section (main) and surface (inset) of 3D printed cellulose object

Cellulose, the main component of paper, is the most abundant organic polymer in the world. It is renewable and biodegradable, easily sourced, and extremely cheap. In our circles, these factors lead to one inevitable question: why aren’t more people trying to 3D print with it? While many scientists have attempted to do so, most have faced one major obstacles: cellulose thermally decomposes when heated, separating its elements before it becomes flowable and thus printable. High-concentration cellulose solutions, on the other hand, are often too viscous to extrude. Fortunately, researchers at MIT have found a different way to use cellulose for 3D printing.

Cellulose acetate, which is used in photography, paint production, and the making of frames for eyeglasses, is widely available as a commodity product, and may hold the key to 3D printing with cellulose. The material has fewer hydrogen bonds due to the presence of acetate groups, and can be dissolved in acetone and extruded through a nozzle. When the acetone evaporates, the cellulose acetate remains solidly in place. Impressively, the MIT researchers have even found a way to restore the missing hydrogen bonds after the 3D printing has taken place.

“After we 3D print, we restore the hydrogen bonding network through a sodium hydroxide treatment,” explains MIT postdoc Sebastian Pattinson, lead author of the research paper documenting the cellulose 3D printing study. “We find that the strength and toughness of the parts we get…are greater than many commonly used materials.” These materials include ABS, PLA, and other 3D printing staples.

3D printed surgical tweezers with antimicrobial functionality

Because the 3D printable cellulose acetate takes the form of an ink, the researchers have also been able to tinker with the solution to create functionally diverse printed objects. For example, by adding antimicrobial dye to the 3D printing solution, they were able to 3D print a pair of surgical tweezers with antimicrobial powers. These 3D printed tweezers killed bacteria in the presence of fluorescent light, and the researchers think they could be used in remote medical settings where it’s difficult to deliver new tools.

One of the main advantages of this cellulose 3D printing process is its speed. Since the cellulose acetate does not need to be heated in order to be extruded, a major step in the 3D printing process is eliminated. Moreover, certain adjustments could make the 3D printing technique even faster: laying down thin ribbons of material to maximize surface area, for instance, or blowing hot air over the 3D printed parts to speed up the process of evaporation. The researchers have also considered developing a system for recovering the evaporated acetone, making the process more cost effective and environmentally friendly.

“Cellulose is the most abundant organic polymer in the world,” Pattinson says, just one factor that could make the cellulose 3D printing technique an extremely attractive commercial proposition. The research paper, “Additive Manufacturing of Cellulosic Materials with Robust Mechanics and Antimicrobial Functionality,” has been published in Advanced Materials. Pattinson authored the study alongside MIT’s A. John Hart.

 

 

Posted in 3D Printing Materials

 

 

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