Cellulose nanocrystals support material for 3D printing complexly shaped structures via multi-materials-multi-methods printing

To fabricate highly complex structures, sacrificial support material is usually needed. However, traditional petroleum-based support materials are un-sustainable, non-recyclable, and difficult to be completely removed from the target structure after 3D processing. Instead, cellulose nanocrystals (CNC) gel could serves as an interesting 3D printing support material due to its sustainability, renewability, and potential recyclability. Since CNCs are highly dispersible in water as nanoparticles and are also not UV sensitive, it has less absorption or bondability with other UV curable polymer matrices. This allows them to be completely washed out by water, which offers a green and efficient method to remove the CNC support material during post processing. In addition, with increasing needs for more intricate structures, combining different 3D printing strategies into a hybrid 3D printing platform can be highly beneficial. In this work, a multi-materials-multi-methods (M4) printer with dual direct-ink-write (DIW) and DIW-inkjet printing capability was used to fabricate various complex structures while using CNC as support material. After 3D printing, water was used to remove the CNC support structure. Even in a highly confined environment, such as the inside of a balloon structure, CNC support material was still easily removed. The potential of using sustainable CNC support material and M4 hybrid 3D printing strategies to fabricate different complex structures was demonstrated. Since CNC gel is derived from forestry products and is entirely water based, the 3D printing process was also made more environmentally friendly, sustainable, and potentially recyclable.