Researchers at MIT have developed a new 3-D printing process using a renewable, biodegradable alternative to the polymers currently used.
Cellulose is the most abundant organic polymer in the world and has been used to produce the most widely used printed-on material—paper. Cellulose is the component in giving wood its mechanical properties. It is inexpensive, biorenewable, biodegradable and very chemically versatile. Cellulose is used in pharmaceuticals, medical devices, as food additives, building materials, clothing and in other applications.
Because of these properties, the material could provide a number of benefits for additive manufacturing because of the ability to individually customize each product that would be made. The idea of using cellulose in 3-D printing is not new but researchers have faced problems when the material is heated leading to it thermally decomposing before becoming flowable.
The MIT team instead worked with cellulose acetate, a material that is made from cellulose and is already produced and readily available. Cellulose acetate can be dissolved in acetone and extruded from a nozzle. As the acetone quickly evaporates, the cellulose acetate solidifies in place allowing objects to be created.
“After we 3-D print, we restore the hydrogen bonding network through a sodium hydroxide treatment,” says Sebastian Pattinson, MIT postdoc. “We find that the strength and toughness of the parts we get… are greater than many commonly used materials” for 3-D printing, including acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA).
Researchers demonstrated the versatility of the production process by adding a small amount of antimicrobial dye to the cellulose acetate ink and 3-D printed a pair of surgical tweezers.
“We demonstrated that the parts kill bacteria when you shine fluorescent light on them,” Pattinson says. This could lead to making custom-made tools for remote medical settings where there’s a need for surgical or customized tools but it is difficult to deliver them. Because the process has antimicrobial properties, it would be an essential tool in places where sterility could not be achieved.
Another benefit to the process is that because it is done at room-temperature, simply relying on the evaporation of the acetone to solidify the part, various methods could speed up the process such as laying down thin ribbons of material to maximize surface area, or blowing hot air over it to speed up evaporation. This could lead to a production system that would be more cost effective and environmentally friendly.