The increasingly personal and ubiquitous capabilities of computing—everything from smartphones to virtual reality—are enabling us to build a brave new world in the digital realm. Despite these advances in the virtual world, our ability as end-users to transform the physical world still remains limited. The emergence of low-cost fabrication technology (most notably 3D printing) has brought us a dawn of making, promising to empower everyday users with the ability to fabricate physical objects of their own design. However, the technology itself is oblivious of the physical world—things are, in most cases, assumed to be printed from scratch in isolation from the real world objects they will be attached to and work with. To bridge this ‘gulf of fabrication’, my thesis research focuses on developing fabrication techniques with design tool integration to enable users to expressively create designs that can be attached to and function with existing real-world objects. Specifically, my work explores techniques that leverage the 3D printing process to create attachments directly over, onto and around existing objects; a design tool further enables people to specify and generate adaptations that can be attached to and mechanically transform existing objects in user-customized ways; a user-driven approach allows people to express and iterate structures that are optimized to support existing objects; finally, a library of ‘embeddables’ demonstrate that existing objects can also augment 3D printed designs by embedding a large variety of material to realize different properties and functionalities. Overall my thesis aspires to make fabrication real—enabling people to express, iterate and fabricate their designs that closely work with real-world objects to augment one another.

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Organ-on-chip models are a rapidly evolving and promising tool for studying human physiology and disease and developing therapeutics. However, due to the lack of fabrication processes of pertinent precision to deliver well-defined architectural and mechanical elements, organ-on-chip models have been limited in recapitulating structural and biomechanical features of many tissues, which has impeded the modeling power and clinical relevance of these tools. The elusive in vitro replication of the pumping function and mechanical loading of the human heart, an outstanding instance of a structurally and mechanically complex physiological system, exemplifies the need for stronger fabrication processes. In this work, we investigated the potential of two-photon direct laser writing (TPDLW), an emerging high-precision fabrication technique, in enabling the generation of structurally and biomechanically complex organ-on-chip models. We first identify the functional principles, advantages and limitations of TPDLW, and review existing applications of TPDLW for in vitro studies. Inspired by the fabrication versatility of TPDLW, we then engineer a microfluidic cardiac pump powered by human stem-cell-derived cardiomyocytes (hiPSC-CM), aiming to replicate the ventricular pumping function on a chip by constructing miniaturized analogues of the functional elements of the human heart. We specifically fabricate a microscale metamaterial scaffold with fine-tuned mechanical properties to support the formation and cyclic contraction of an unprecedentedly miniaturized induced pluripotent stem cell derived ventricular chamber. Furthermore, we fabricate microfluidic valves with extreme sensitivity to rectify the flow generated by the ventricular chamber. The integrated microfluidic system recapitulates ventricular fluidic function and exhibits for the first time in vitro all phases of the ventricular hemodynamic loading pattern. Finally, we demonstrate a technique of increasing the fabrication output of TPDLW that could enable its broader adoption. Together, our results highlight the potential of high-precision fabrication in expanding the accessible spectrum of organ-on-a-chip models towards structurally and biomechanically sophisticated tissue architectures. This dissertation is accompanied by a set of supplementary videos depicting the results of our experimental efforts. Movie 1 shows a cardiac tissue beating on an inverted hexagon scaffold. Movie 2 shows a compressive test on helical scaffold that is later embedded in a cardiac tissue. Movie 3 show a beating cardiac chamber on helical scaffold that can generate measurable flow. Movie 4 shows a functional suspension valve that is later embedded in the device with the cardiac chamber. Movie 5 shows the function of a suspension valve that rectifies oscillating flow. Movie 6 shows that the same suspension valve can rectify flow of increasing frequency. Movie 7 shows that the combined chamber and valves exhibit directional flow. Finally, movie 8 shows that the addition of afterload in the combined system leads to the emergence of isovolumetric phases. / 2023-09-24T00:00:00Z

archives@tulane.edu / The goal of this research was to establish a novel digital manufacturing-based workflow for the fabrication of membrane free organ chip (MFOC) systems. This workflow is based on the implementation of top-down design, starting with CAD design of molds for MFOC components and can be conducted on a benchtop removing the need for cleanroom use. In conducting this research, a commercially available SLA printer was characterized and optimized for manufacturing molds suitable for MFOC fabrication. To achieve this, extensive research was required to determine printer resolution limits and work within the limitations of the resins available for printing. Specifically, the molds need to be flat and smooth in order to produce perfectly horizontal and transparent PDMS devices. Post-processing workflows were engineered to satisfy these MFOC design constraints. After establishing a reliable and reproducible workflow for MFOC fabrication, the focus of the research was reduction to practice, i.e. achieving a design that enables loading MFOC with patterned aqueous solutions with 100% success and a high degree of forgiveness. Key MFOC dimensions were systematically varied in a manner only possible with the rapid prototyping capability of DM in a series of experiments with a standardized injection test and success rate of loading as the primary output. With a robust MFOC design in place, more complex designs for tissue patterning applications were created, and advanced configurations for engineering patterned vascularized stromal tissues were tested and validated. Seqeuntial and simultaneous loading scenerios were imvestigated to better understand cell migration impedence in multi-gel lane devices. / 1 / William Bralower

This thesis reports the development of BioMe, a co-culture microplate platform that enables high-throughput, real-time quantitative growth dynamics measurements of interacting microbial batch cultures. The primary BioMe components can be 3D-printed, allowing ease of fabrication and DIY accessibility in the microbiome community. A pairwise 3D-printed iteration of the BioMe device was used in diffusion and co-culture experiments. Genetically engineered Escherichia Coli lysine and isoleucine auxotroph strains were used to characterize the diffusion of amino acids across the porous membranes. Results demonstrated a nonlinear relationship between growth rate and pore size and also distinct diffusion behavior for lysine and isoleucine. Pairwise syntrophic co-culture experiments demonstrated synergistic but repressed interaction between these two paired auxotrophs. Investigation of the effect of varying initial amino acid conditions on growth dynamics demonstrated that small changes in initial media condition can consistently affect patterns of yield and growth rate of constituent microbial species. / 2020-08-30T00:00:00Z

STATEMENT OF PROBLEM: The production of full arch dental models through Rapid Additive Prototyping (3D Printing) have been questioned for their accuracy in the past decade. PURPOSE: To compare the accuracy of 3D printed and milled dental models, using a digital metrology software. MATERIALS AND METHOD: A mandibular arch typodont was duplicated to produce a conventional Type IV dental stone model. This Model was scanned to create a digital model and an STL file was created which would be sent to Milling and 3D printing machines.15 models were printed using 3 different 3D printing companies and 10 models Milled with a CNC (Computerized Numeric Controlled) milling machine. Each model was scanned and a digital model was created. These scanned models were then super imposed to the scan of the master model through an inspection software (Geomagic Control X, 3D Systems) for accuracy of production. RESULTS: The mean difference in measurement in Absolute Gap, by either of the two methods of prototyping adopted, (0.075 mm for 3D Printed and 0.084 mm for milled) are well below the clinically acceptable values mentioned in previous literature. The means in absolute tooth distance discrepancy for both prototyping methods (0.0361 mm for 3DPand 0.0353 mm for Milled) were not statistically significant. CONCLUSION: 3D printed dental models were more accurate statistically than milled dental models. In general, the mean accuracy for both methods of rapid prototyping is within clinical tolerance and both are clinically acceptable.

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Building upon previous research on Digital Light Projection (DLP) 3D printing for microfluidics, in this thesis I performed the detailed design and fabrication of a novel DLP 3D printer to increase resolution and device footprint flexibility. This new printer has a pixel resolution twice that of our group’s previous printers (3.8 μm vs 7.6 μm). I demonstrated a new state of the art for minimum channel width, reducing the minimum width to 15 μm wide (and 30 μm tall). This is an improvement over the previous smallest width of 20 μm. This printer also has the capacity to perform multiple spatially distinct exposures per printed layer and stitch them into one interconnected device. Image stitching enables printing devices with identical build areas to previous printers, and with smaller pixel pitch. I pursued validation of this stitching capacity by fabricating channel devices with features crossing the stitched image boundary, with the goal of printing channels that would flow fluid consistently and without leaking. To accomplish this, I began by characterizing the print parameters for successfully printing single microfluidics channels across the stitched image boundary, and then I explored the sensitivity of my method to multiple crossings of the image boundary by printing a stacked serpentine channel that crossed the stitched image boundary 392 times. This demonstrated that an arbitrary number of stitched boundary crossings are feasible and thus a high degree of complex device component integration across these boundaries is also possible. These developments will be useful in future research and design of 3D printed microfluidic devices.

Indianapolis / In this thesis, cellulose nanofiber (CNF) reinforced polylactic acid (PLA) filaments were produced for 3D printing applications using melt extrusion. The use of CNF reinforcement has the potential to improve the mechanical properties of PLA, making it a more suitable material for various 3D printing applications. To produce the nanocomposites, a master batch with a high concentration of CNFs was premixed with PLA, and then diluted to final concentrations of 1, 3, and 5 wt% during the extrusion process. The dilution was carried out to assess the effects of varying CNF concentrations on the morphology and mechanical properties of the composites. The results showed that the addition of 3 wt.% CNF significantly enhanced the mechanical properties of the PLA composites. Specifically, the tensile strength increased by 77.7%, the compressive strength increased by 62.7%, and the flexural strength increased by 60.2%. These findings demonstrate that the melt extrusion of CNF reinforced PLA filaments is a viable approach for producing nanocomposites with improved mechanical properties for 3D printing applications. In conclusion, the study highlights the potential of CNF reinforcement in improving the mechanical properties of PLA for 3D printing applications. The results can provide valuable information for researchers and industries in the field of 3D printing and materials science, as well as support the development of more advanced and sustainable 3D printing materials.