Title: Shape Morphing and Graded Multinozzle 3D Printheads for Rapid 3D Printing of Soft Matter

Abstract: Embedded 3D printing is a versatile platform for fabricating soft matter, but its dominant paradigm - a single nozzle depositing a single material along a single path - is ill suited for branching architectures and high-throughput manufacturing and materials exploration. Branched architectures like vascular trees require repeated stops, revisits, and non-printing travel, which introduces disconnections that compromise fidelity and perfusability. Multinozzles exist in parallelizing throughput, however, existing designs are bulky, static, and constrained to extruding the same material through every tip. Furthermore, exploring material design spaces for soft matter often requires printing and testing dozens of formulations, each of which are prepared serially. In this thesis, I develop two multinozzle platforms that overcome these limits along two themes: geometric programmability, and compositional programmability. 

Part one presents high-throughput dendritic robotic actuator (HYDRA), a shape-morphing dendritic printhead that deploys nested generations of nested generations of pre-curved nitinol tubes that dynamically splay and converge during a print, drawing on mechanics of concentric tube robots. Trifurcating (3²=9 terminal branches) and bifurcating (2³=8 terminal branches) designs achieve 0.3 mm of tip placement repeatability, with trifurcating achieving 99% fabrication efficiency versus 52% for single-nozzle strategies. I demonstrate HYDRA across three matrices, sacrificial writing into into HEK293-laden hydrogels, cardiac organoid fibrin constructs, and endotheliazable hierarchical channels in gelatin granular matrices producing connected vascular trees within engineered tissue and tissue-like constructs, and specifically in occluded spaces like molds. 

Part two extends the gradient embedded multinozzle (GEM) printhead platform, previously developed in our lab, to three- and four-input combinatorial mixing through microfluidic-inspired Baker’s Map mixing elements that distribute mixed outputs across a parallel nozzle array. I derive both scaling and mixing theory governing GEM design - relating input number and outlet nozzle count and predicting the compositional blends achieved, and contextualize experimental results with modifications to the theory. Furthermore, using a three-way GEM Nozzle, I printed 10 compositions of di- and multi-functionalized poly(ethylene-glycol) diacrylate hydrogel tri-leaflet valves, optimizing over stiffness, swelling ratio, tensile strength, and toughness, and ultimately testing an optimal blend in an in-vitro heart simulator. These GEM multinozzles are compatible with either pressure- or volume-driven extrusion systems, and compresses the ink-formulation cycle from sequential to parallel. 

Together, HYDRA and GEM reframe the multinozzle as an active, programmable instrument, rather than a passive manifold, advancing embedded 3D printing for soft matter towards scalable manufacturing and high-throughput materials exploration. 

Please contact Leyre Caracuel for the Zoom link.