The microstructural characteristics

The microstructural characteristics of HB permitted fibers to undergo various modes of deformation while being able to recover almost com- pletely upon unloading (Fig. 3A and fig. S4). In all instances, macroscopic deformation resulted from the elastomer matrix straining under loads, pulling and pushing embedded particles along with it. Porosity within therepresentation of proposed HA and elastomer distribution within fibers with single- or graded-solvent mixtures, as a function of time after extrusion. Higher-magnification SEM micrographs of DCM solvent only (F) and HAPCL microstructures (G). Details regarding material compositions and prepara- tions can be found in Table 1.fibers enabled rigid particles to translate while limiting direct, incompressible interactions with each other. Upon compressive loading, excess pore space was eliminated as particles flowed with the straining elastomer to fill the open volume. Tensile loads were carried almost entirely by the elas- tomer, and under extreme strains, temporary separation between the elas- tomer and particle surfaces occurred (fig. S4E). However, because the HA particles were physically encapsulated within the elastomer and not co- valently bound to it, these interfacial tensile voids were not permanent and disappeared upon unloading. The elastomer produced antiparallel restoring forces upon unloading, which manifested itself as a macro- scopically observable elastic response (large, recoverable deformation), with the HB returning to near-net shape over many cycles (fig. S4, D and G). For porous HB constructs that were 3D-printed into defined archi- tectures, the previously defined compression, tension, and bending de- formation modes were combined to impart elastic properties throughout the entire construct. Although the geometry and porosity of the 3D- printed object affected the ultimate mechanical behavior, simple 90° cyl- inders (printed fibers oriented perpendicular to adjacent layers) could be cyclically compressed up to 40% strain and rapidly returned to near- original form immediately after each cycle (Fig. 3A), with full recovery occurring over the course of minutes (fig. S4H). This behavior was not limited to quasi-static loading but is also evident under dynamic loading, such as a hammer impact; 3D-printed HB constructs, despite being com- posed of 90 weight % (wt %) ceramic, did not shatter, catastrophically fail, or permanently deform under high-impact loads (unlike hot- melt printed samples) but, rather, rebounded to their original form (movie S3).