Page 52 - Plastics News March 2017

TEChNoLoGy

Plants can replace polymers - introducing 3-D printing with cellulose

ellulose, that for centuries, has formed the basis and toughness of the parts we get ... are greater than
Cof the most abundantly printed-on material: paper, many commonly used materials" for 3-D printing, including
may also become an abundant material to print with in acrylonitrile butadiene styrene (ABS) and polylactic acid
3D Printing. Thus, potentially providing a renewable, (PLA). To demonstrate the chemical versatility of the
biodegradable alternative to the polymers currently production process, Pattinson and Hart added an extra
used in 3-D printing materials, thanks to new research dimension to the innovation. By adding a small amount
at MIT. "Cellulose is the most abundant organic polymer of antimicrobial dye to the cellulose acetate ink, they
in the world," says MIT postdoc Sebastian Pattinson, 3-D-printed a pair of surgical tweezers with antimicrobial
lead author of a paper describing the new system in functionality.
the journal Advanced Materials Technologies. Because "We demonstrated that the parts kill bacteria when you
it is inexpensive, biorenewable, biodegradable, shine fluorescent light on them," Pattinson says. Such
and chemically versatile, it finds application in custom-made tools "could be useful for remote medical
pharmaceuticals, medical devices, as food additives, settings where there's a need for surgical tools but it's
building materials, clothing, etc. Pattinson added, "...a difficult to deliver new tools as they break, or where
lot of these kinds of products would benefit from the there's a need for customized tools.
kind of customization that additive manufacturing [3-D
printing] enables." The paper is co-authored by associate And with the antimicrobial properties, if the sterility of the
professor of mechanical engineering A. John Hart, the operating room is not ideal the antimicrobial function could
be essential," he says. 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.
This room-temperature cellulose
process, which simply relies on
evaporation of the acetone to
solidify the part, could potentially
Mitsui Career Development Professor in Contemporary be faster, Pattinson says. And various methods could speed
Technology. it up even further, such as laying down thin ribbons of
material to maximize surface area, or blowing hot air
The MIT team chose to work with cellulose acetate - a over it to speed evaporation. A production system would
material that is easily made from cellulose and is already also seek to recover the evaporated acetone to make the
widely produced and readily available. Essentially, the process more cost effective and environmentally friendly.
number of hydrogen bonds in this material has been
reduced by the acetate groups. Cellulose acetate can be Cellulose acetate is already widely available as a
dissolved in acetone and extruded through a nozzle. As commodity product. In bulk, the material is comparable
the acetone quickly evaporates, the cellulose acetate in price to that of thermoplastics used for injection
solidifies in place. A subsequent optional treatment molding, and it's much less expensive than the typical
replaces the acetate groups and increases the strength filament materials used for 3-D printing, the researchers
of the printed parts. "After we 3-D print, we restore the say. This, combined with the room-temperature conditions
hydrogen bonding network through a sodium hydroxide of the process and the ability to functionalize cellulose in
treatment," Pattinson says. "We find that the strength a variety of ways, could make it commercially attractive.

Plastics News | March 2017 52