Three-dimensional (3D) printing of hierarchically ordered cellular materials with tunable microstructures is a major challenge from both synthesis and scalable manufacturing perspectives. A simple, environmentally friendly, and scalable concept to realize morphologically and microstructurally engineered cellular ceramics is herein demonstrated by combining direct foam writing with colloidal processing. These cellular structures are widely applicable across multiple technological fields including energy harvesting, waste management/water purification, and biomedicine. Our concept marries sacrificial templating with direct foaming to synthesize multiscale porous TiO2 foams that can be 3D printed into planar, free-standing, and spanning hierarchical structures. The latter being reported for the first time. We show how by varying the foam-inks’ composition and frothing conditions, the rheological properties and foam configurations (i.e., open- or closed-cell) are tuned. Furthermore, our printing studies indicate a synergy between intermediate extrusion pressures and low speeds for realizing spanning features. Additionally, the dimensional changes associated with the postprocessing of the different foam configurations are discussed. We investigate the effects of the foams’ composition on their microstructure and surface area properties. Additionally, the foams’ photocatalytic performance is correlated with their microstructure, improving for open-cell architectures. The proposed synthesis and scalable manufacturing method can be extended to fabricate similar structures from alternative ceramic foam systems, where control of the porosity and surface properties is crucial, demonstrating the great potential of our synthesis approach.

The Nakahara Effect and its Influence on Solution-Based 3D Printed Films Daryl Kwakye-Ackah Motivated by the Nakahara Effect, the influence of altering printing parameters on fragmentation mechanism(s) of directly written titanium dioxide(TiO 2) films is investigated. The Nakahara effect states that a long lasting memory can be introduced into a colloidal system prior to drying, affecting the type of crack pattern formed due to externally applied forces. TiO 2 has important applications due to its interesting semiconducting properties, tunable band gap, photocatalytic properties, biocompatibility, and relative abundance. This is the reason it is used in this project as a model printing ink system. In this research, two deposition methods (i.e. direct-ink writing and doctor-blading) were compared in order to study the Nakahara Effect. In particular, the focus was to investigate the effects of film thickness, drying process used and the concentration of primary TiO 2 particles in the aqueous ink on drying crack pattern formation. Crack patterns were observed during drying using an optical microscope, and crack lengths were measured using image analysis. Weibull statistics were used to study variability in crack patterns for the different deposition methods. The results suggest a distinction between the printed and doctor-bladed samples hence demonstrating the validity of the Nakahara Effect. They also provide new insights for the role of direct writing parameters for inducing distinct printing memory characteristics that may help to further understand and minimize crack formation during drying.