The additive manufacturing of ceramic composites with tailored microstructures is still challenging and timeconsuming. However, there is great interest as it may enable the implementation of novel materials architectures following computer designs. In this work, we demonstrate a straightforward method to obtain ceramics
with a network of continuous weak interlayers designed to increase fracture resistance using alumina as a model
system. This is achieved by combining direct ink writing with the coextrusion of multi-material pastes with
carefully matched rheology based on thermally reversible hydrogels and inorganic powders. The printed Al2O3
bars with and without weak interlayers exhibit strengths ranging between 180 and 360 MPa and KIC ~ 3
MPa•m1/2. The introduction of weak interlayers using different raster patterns, such as length wise and Bouligand alignments can be used to direct crack propagation and promote gradual failure. The result is an
improvement in the fracture energy up to 230 J/m2 and KJ up to 9 MPa⋅m1/2. These results suggest the potential
of manufacturing ceramics with enhanced mechanical properties by using robocasting with multi-material inks
to engineer complex interlayer networks.