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.
Extreme weather phenomena are on the rise due to ongoing climate change. Therefore, the need for irrigation in agriculture will increase, although it is already the largest consumer of water, a valuable resource. Soil moisture sensors can help to use water efficiently and economically. For this reason, we have recently presented a novel soil moisture sensor with a high sensitivity and broad measuring range. This device does not measure the moisture in the soil but the water available to plants, i.e., the soil water potential (SWP). The sensor consists of two highly porous (>69%) ceramic discs with a broad pore size distribution (0.5 to 200 μm) and a new circuit board system using a transmission line within a time-domain transmission (TDT) circuit. This detects the change in the dielectric response of the ceramic discs with changing water uptake. To prove the concept, a large number of field tests were carried out and comparisons were made with commercial soil water potential sensors. The experiments confirm that the sensor signal is correlated to the soil water potential irrespective of soil composition and is thus suitable for the optimization of irrigation systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.