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The transmission of longitudinal ultrasonic waves through periodic ceramic microlattices fabricated by Robocasting was measured in the 2-12MHz frequency range. It was observed that these structures (scaffolds of tetragonal and hexagonal spatial arrangements with periodicity at length-scales of ∼100μm) exhibit well-detectable acoustic band structures with bandgaps. The locations of these gaps at relatively high frequencies were shown to be in close agreement with the predictions of numerical models, especially for tetragonal scaffolds. For hexagonal scaffolds, a mixing between longitudinal and shear polarizations of the propagation modes was observed in the model, which blurred the matching of the calculated band structures with the experimentally measured bandgaps.

Ultrasonic measurements combined with numerical modelling are used to analyze the elastic and acoustic properties of morphologically complex ceramic bodies assembled by the Robocasting technique. It is shown that the micromechanics of the robocast periodic scaffolds leads to several metamaterial-like wave propagation phenomena. Besides the expectable prominent elastic anisotropy and the frequency band structure resulting from the periodicity of the scaffold, a wave-mode mixing is observed that disables the conventional distinguishing between quasi-longitudinal, quasi-shear, and pure shear modes for propagation in the symmetry planes of the structure. This paper proves the capability of Robocasting, as a versatile three-dimensional (3D) printing method, to produce tailored acoustic metamaterials with very low damping and outstandingly strong acoustic anomalies.

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