Dedicated
hierarchical structuring of functional ceramics can be
used to shift the limits of functionality. This work presents the
manufacturing of highly open porous, hierarchically structured barium
titanate ceramics with 3-3 connectivity via direct
ink writing of capillary suspension-type inks. The pore size of the
printed struts (∼1 μm) is combined with a printed mesostructure
(∼100 μm). The self-organized particle network, driven
by strong capillary forces in the ternary solid/fluid/fluid ink, results
in a high strut porosity, and the distinct flow properties of the
ink allow for printing high strut size to pore size ratios, resulting
in total porosities >60%. These unique and highly porous additive
manufactured log-pile structures with closed bottom and top layers
enable tailored dielectric and electromechanical coupling, resulting
in an energy harvesting figure of merit FOM33 more than
four times higher than any documented data for barium titanate. This
clearly demonstrates that combining additive manufacturing of capillary
suspensions in combination with appropriate sintering allows for creation
of complex architected 3D structures with unprecedented properties.
This opens up opportunities in a broad variety of applications, including
electromechanical energy harvesting, electrode materials for batteries
or fuel cells, thermoelectrics, or bone tissue engineering with piezoelectrically
stimulated cell growth.