Hydrogel-Particle Interaction-Powered Embedded Ink Writing: from Material Design to Biomedical Applications

Abstract

This dissertation addresses two critical challenges in embedded ink writing (EIW): prolonged fabrication times and restricted printing feature sizes. Initially, advanced strategies for designing novel support bath materials tailored specifically for EIW applications are explored. By developing nanoclay-based hydrogel nanocomposites incorporating sodium alginate (NaAlg), polyethylene glycol diacrylate (PEGDA), and Pluronic F127, versatile control over rheological properties was achieved, addressing constraints in printable feature sizes and printing speeds. Nanoclay-Pluronic F127 composites demonstrated robust thermoresponsive behaviors, ideally suited for dynamic printing processes.Subsequently, fundamental mechanisms governing material interactions and filament formation essential for optimizing EIW processes were systematically investigated. Detailed analyses revealed how electrostatic, jammed, and polymer chain interactions influenced the microstructure and rheology of nanocomposites. Six distinct filament categories were identified, with a novel position-shape-size (PSS) evaluation framework introduced to comprehensively assess filament viability, enhancing precision and resolution. Building on these insights, innovative EIW strategies-Multiscale Embedded Printing (MSEP) and High-Speed Embedded Ink Writing (HS-EIW)-were developed. MSEP enabled precise multiscale fabrication of complex organ structures, significantly improving dimensional accuracy and surface smoothness, exemplified by printing sophisticated anatomical models. HS-EIW dramatically reduced fabrication times by leveraging optimized nanoclay-hydrogel support baths, demonstrated by the rapid production of anatomically accurate human kidney analogs. Finally, these advancements were successfully translated into critical biomedical applications, notably surgical planning and diagnostic precision. The developed stimuli-responsive support baths facilitated fabrication of patient-specific brain tumor models and realistic lung cancer diagnostic tools, improving surgical outcomes and diagnostic accuracy. Future research will focus on further refining biocompatibility and incorporating living cellular components, thereby enhancing the translational potential of these technologies in personalized medicine and regenerative therapies.