Bones represent a superb biomaterial that combines high mechanical stiffness with nutrition delivery to its osteocyte cells through the microscopical Haversian canals and bone canaliculi. Such a structure is hard to reproduce artificially, though. 3D printing delivers an unprecedented shape control of the created objects. Yet the resolution limit of the most common 3D printers is insufficient, lying between tens to hundreds of microns, while more precise 3D printing techniques fail in fabricating larger objects. We present a unique, yet simple and versatile method for preparing hierarchically aligned microporous canals using a biocompatible polymer polylactic acid (PLA) with their structure controlled at the submicron to macro scale. The layout was inspired by the microscopical Haversian canals and bone canaliculi of cortical bone. This procedure takes advantage of the PLA complex crystalline behavior, which was pre-oriented by 3D printing, orientedly crystallized in CO2, foamed, and cryo-shrunk. The canal formation was assessed via WAXS, FTIR spectroscopy, and DSC and complemented by the evaluation of mechanical properties, biocompatibility, and directionally selective capillary transport in the final structure. The fine dimensions of the canals unmatched by the common 3D printing techniques capable of making macroscale objects combined with the abovementioned properties represent promising potential for various applications, such as advanced cell-supporting designs with a built-in nutrition function.

Central European Institute of Technology Brno University of Technology Purkyňova 656 123 612 00 Brno Czech Republic

Contipro a s Dolní Dobrouč 401 561 02 Dolní Dobrouč Czech Republic

Faculty of Chemistry Brno University of Technology Purkyňova 118 612 00 Brno Czech Republic

Faculty of Mechanical Engineering Brno University of Technology Technická 2896 2 616 69 Brno Czech Republic

University of Massachusetts Amherst 120 Governors Drive Amherst MA 01003 USA

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