Free-polymer-induced Gelation of Non-aqueous Colloids for Direct Ink Writing

ISSN online 2612-4882
ISSN print 2612-4408
Hiroya Abea, Akira Kondoa, Kazuyoshi Satob
aOsaka University, Joining and Welding Research Institute, Osaka, Japan
bGunma University, Graduate School of Science & Technology, Gunma, Japan


Direct ink writing (DIW) facilitates the fabrication of three-dimensional (3D) green structures through the layer-by-layer deposition of colloidal gel-based inks. Several gel designs have been developed for aqueous systems. Here, we report a facile gelation method for a non-aqueous system: Y2O3-stabilized ZrO2 (YSZ) particles dispersed in ethanol. First, fluidic and concentrated YSZ colloids were prepared using polyethyleneimine (PEI) as a dispersant. Then, a fluid-to-gel transition was triggered by adding polyvinyl butyral (PVB) as a free polymer. The resulting colloidal gels had a viscoelastic response adequate for DIW. Further analysis revealed that the depletion flocculation mechanism plays an important role on this gelation. Moreover, using the non-aqueous colloidal gel, a helical coil structure of ~100 µm dimeter was patterned via the deposition of a continuous filament extrusion through a cylindrical nozzle in a water reservoir. During the deposition, a PVB film was formed in situ on the surface of the filament because of the poor solubility of PVB in water, which was used to avoid variations in the ink rheology owing to unexpected ethanol evaporation. The present methodology may be a useful route for the engineering of 3D green structures.
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