Concentric Push-Pull Tube Robots for Embedded 3D Printing

The global shortage of transplantable organs has spurred significant interest in organ 3D printing as a method to fabricate patient-specific tissues and complex biological structures. However, this field faces persistent technical challenges, particularly in achieving the high levels of spatial precision and printing speed necessary to preserve cell viability during fabrication. Recent innovations in bioprinting have begun integrating continuum robotic systems to enhance nozzle control within viscoelastic support matrices, enabling the creation of intricate forms. Among these systems, Concentric Tube Robots (CTRs) have shown promise due to their dexterity and compactness, yet their reliance on pre-curved tubes and coupled rotational actuation introduces kinematic complexity, limits path predictability, and restricts the ability to achieve fully straight or variable curvature configurations. This thesis introduces a novel Concentric Push-Pull Robot (CPPR) system as an alternative robotic architecture for embedded 3D printing. CPPRs utilize purely translational actuation between concentrically nested tubes to generate bidirectional bending, eliminating the torsional coupling issues associated with CTRs. Integrated into a universal continuum robot platform capable of supporting diverse tube geometries, the CPPR system was optimized through a custom MATLAB-based notch design algorithm and fabricated via stereolithography (SLA) resin printing. Rheological analysis led to the identification of an ideal material pairing—a 6 wt.% fumed silica support matrix and a 4 wt.% epoxy print ink—that enabled high-fidelity embedded printing. The robot’s motion was calibrated using digital image correlation (DIC) and tested through repeated tracking of a complex star-shaped path. The CPPR system was then used to successfully print a nested dual-vase structure, demonstrating its ability to extrude material within occluded, non-convex geometries—capabilities that surpass what is possible with conventional linear nozzles. This thesis establishes the CPPR as a promising tool for embedded bioprinting, offering advantages in print accessibility, actuation simplicity, and material compatibility. By enabling continuous extrusion along complex trajectories within constrained environments, the CPPR platform expands the design space for fabricating anatomically relevant features such as vascular networks and internal cavities. These contributions provide a foundation for future developments in bioprinting systems that are faster, more precise, and better suited for producing viable, patient-specific tissues and organs.