Micro-reactive inkjet printer for 2D and 3D hydrogel structures

Inkjet printing, the digitally-controlled deposition of microdroplets onto a substrate, demonstrates a number of potential applications as a polymer additive manufacturing technique due to a relatively high spatial resolution and the ability to deposit multiple materials in one structure. It is, however, fundamentally limited by the low viscosity of the printed ink, which restricts both the use of colloidal suspensions or necessitates the use of post-deposition treatment of the ink to form the structure. Herein, micro-reactive inkjet printing attempts to circumvent these limitations by exploiting the controlled in-air collision of two reactive microdroplets, so as to produce a microdroplet of the desired product before deposition onto substrate, thereby facilitating polymer synthesis and patterning in a single step. In this work, we fabricated a series of 3D structures using a model system based upon alginate-based hydrogel. The formation of hydrogel structures was achieved by the reaction of crosslinker and gelator, and demonstrated deposition rates significantly faster than previously reported. Potential work considering the spatial variation of material composition by varying reaction stoichiometry will also be discussed.