A group of researchers at Chalmers University of Technology have managed to print and dry 3D objects made entirely by cellulose for the first time with the help of a 3D-bioprinter. They also added carbon nanotubes to create electrically conductive material. The effect is that cellulose and other raw material based on wood will be able to compete with fossil-based plastics and metals in the on-going additive manufacturing revolution, which started with the introduction of the 3D-printer.
3D printing is a form of additive manufacturing that is predicted to revolutionise the manufacturing industry. The precision of the technology makes it possible to manufacture a whole new range of objects and it presents several advantages compared to older production techniques.
“Cellulose is an unlimited renewable commodity also it is completely biodegradable, and manufacture using raw material from wood, and also to bind carbon dioxide that would otherwise end up in the atmosphere.”
The difficulty using cellulose in additive manufacturing is that cellulose does not melt when heated. Therefore, the 3D printers and processes designed for printing plastics and metals cannot be used for materials like cellulose.
The Chalmers researcher solved this problem by mixing cellulose nanofibrils in a hydrogel consisting of 95-99 percent water. The gel could then in turn be dispensed with high fidelity into the researchers’ 3D bioprinter.
The next challenge was to dry the printed gel-like objects without them losing their 3D shape.
Since the drying process is critical, they have developed a process in which freeze the objects and remove the water by different means as to control the shape of the dry objects. It is also possible to let the structure collapse in one direction, creating thin films.”
Furthermore, the cellulose gel was mixed with carbon nanotubes to create electrically conductive ink after drying. Carbon nanotubes conduct electricity, and another project at Wallenberg Wood Science Center aims at developing carbon nanotubes using wood.
Using the two gels together, one conductive and one non-conductive, and controlling the drying process, the researchers produced three-dimensional circuits, where the resolution increased significantly upon drying.
The two gels together provide a basis for the possible development of a wide range of products made by cellulose with in-built electric currents.
“Potential applications range from sensors integrated with packaging, to textiles that convert body heat to electricity, and wound dressings that can communicate with healthcare workers,” says lead researcher Paul Gatenholm. “Our research group now moves on with the next challenge, to use all wood biopolymers, besides cellulose.
The research findings were presented at the conference New Materials From Trees that took place in Stockholm, Sweden, on June 15-17.
