Model Design and Path Optimization of Perfusable Chips in Extrusion-Based Bioprinting: Linking Hydrogel Rheology with Structural Features

Extrusion-based bioprinting enables precise spatial control over bioink deposition and offers the advantages of cost-effectiveness, versatility, and biocompatibility. While extensive research has focused on assessing bioink printability and developing printing techniques, limited attention has been directed toward the interplay among material properties, structural design, and process optimization. In this study, the relationships among the rheological behavior of the hydrogel, structural characteristics of models, and planning strategies of the path were systematically investigated. The printability of low- and high-viscosity hydrogels was evaluated through the fabrication of pattern arrays and three-dimensional (3D) grid constructs. Results indicated that low-viscosity hydrogels were more suitable for patterns involving frequent extrusion state transitions, whereas high-viscosity hydrogels facilitated steady-state, long-duration printing of three-dimensional scaffolds. To further explore structure-specific path planning, a perfusable chip comprising flat, support, wall, and overhanging features was designed and printed. To address the inherent limitations of conventional 3-axis bioprinting in fabricating large-scale unsupported overhangs, the printing path was optimized according to the rheological properties of hydrogels. Using this strategy, a 10 × 10 mm² overhanging structure was successfully fabricated, and perfusable hydrogel chips with tunable fluid flow were produced. The chips exhibited reliable flow performance and sealing capacity with a maximum burst pressure of 1.2 kPa. Collectively, this work presents a design framework that integrates material properties with structural features to optimize path planning and printing processes, offering valuable insights for the construction of advanced 3D cell culture systems via extrusion-based bioprinting.