Erick Bandala

Creating multilayered channels for mimicking human blood vessels in thick tissues is the main challenge to overcome in organ biofabrication. Current three-dimensional (3D) printing strategies cannot effectively manufacture hollow channels with multiple layers. This study aims to propose a coaxial nozzle-assisted embedded 3D printing method in which core–shell filaments can be formed in a yield-stress matrix bath by extruding different ink materials through the corresponding channels. The materials selected for the core ink, shell ink, and matrix bath are Pluronic F127 (F127) and calcium chloride (CaCl2), sodium alginate (NaAlg), and poly(ethylene glycol) diacrylate (PEGDA) and nanoclay, respectively. After crosslinking the matrix bath and shell, the core layer made from the sacrificial ink (F127) is removed to generate a single-layered, hollow channel. In this work, the effects of ink material properties and operating conditions on core–shell filament formation have been systematically studied. The rheological and mechanical properties of the yield-stress matrix bath have been characterized as well. A thick tissue-like structure with embedded single-layered, hollow channels has been successfully printed for demonstration. Since it is feasible to design coaxial nozzles with a core–shell–shell architecture, the proposed method is technically extendable to create double-layered channels within a cellular tissue construct, accurately mimicking human blood vascular networks in thick tissues in the future.

Smart hinges fabricated using three-dimensional (3D) printing have been accepted in the aerospace, robotics, and biomedical fields since these devices possess a shape memory characteristic. Shape memory polymers (SMPs) are the preferred materials for creating smart hinges due to their ability to achieve programmable complex geometries. However, fabricating SMPs with embedded components remains a challenge due to the constraints of current 3D printing methods and material limitations. This study investigated the use of a hybrid 3D printing method, direct ink writing (DIW), and embedded 3D printing (e-3DP) to print smart hinges with an embedded circuit to act as a strain sensor. The main components of the SMP included tert-Butyl acrylate (tBA) and aliphatic urethane diacrylate (AUD), but this SMP ink had a low viscosity and could not be used for DIW or e-3DP. Fumed silica (FS) was added to the SMP to tune its rheology, and it was shown that the FS concentration significantly affected the rheological properties, dry-out process, filament geometries, and self-supporting capabilities. This study presents a hybrid 3D printing approach for creating smart hinges with internal strain sensors in one step, demonstrating the versatility of DIW/e-3DP. The findings from this work provide a foundational and reliable technical solution to efficiently fabricate functional, self-monitoring, smart devices from SMPs for diverse applications.