3D-Printing is a race between the instabilities arising from gravitational and interfacial forces that destabilize the printed structure and the solidification of the printed material. For thermoplastics, this solidification often occurs within a few seconds of the ink leaving the printing nozzle, and these instabilities can be generally ignored. However, soft materials, including hydrogels, biopolymers, silicone elastomers, and cellular structures, are often printed in their fluid phase and can have solidification times that order on minutes, hours, or even days. Even after they've solidified, the structures may be too delicate to handle or even support their own weight. Until recently, it was practically impossible to reproducibly shape these soft materials into complex 3D structures with high spatial resolution and small feature sizes. However, new methods in soft matter manufacturing have been recently developed to enable the 3D-printing of soft materials through the use of sacrificial support baths to provide mechanical stability to the fluid phases both during the printing process and throughout the solidification of the printed structure.
During my doctoral studies at the University of Florida, I helped pioneer the use of packed microgels as sacrificial support materials to enable the 3D-printing of various soft materials in their fluid phase. Our approach leveraged the jamming behavior of packed microgel particles at relatively low polymer concentrations to provide the mechanical stability to the 3D-printed structures. Under low applied stresses, these packed microgel particles behave like an elastic solid; however, when an applied stress exceeds the yield stress, the packed microgel will locally yield, behaving like a viscous fluid. This rapid and spontaneous transition between the solid and liquid phase enables a printing nozzle to traverse through the support material and deposit the desired material. My doctoral thesis was focused on designing new aqueous and organic microgel particles and applying them as sacrificial support materials for soft matter 3D-printing, bioprinting, and 3D cell culture applications.