Development and Optimization of High-resolution Additive Manufacturing towards Implantable Biomedical Devices

Ware, Henry Oliver Tenadooah

doi:https://doi.org/10.21985/n2-jz7j-nx51

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Development and Optimization of High-resolution Additive Manufacturing towards Implantable Biomedical Devices

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In recent years Additive Manufacturing (also known as 3D printing) processes have risen in use within research and industry to create complex, custom parts, which would be otherwise too expensive or even impossible to fabricate via conventional manufacturing methods. While originated as a tool for rapid prototyping, the improvements in its precision and materials selections has rapidly transformed 3D printing for direct manufacturing of end-use products. The most popular forms of 3D print consist of materials extrusion, selective laser sintering and directed energy deposition, and photopolymerization. Its ability for quickly adopting design changes make 3D printing an attractive candidate for customizing biomedical implants fit specifically to individual patient’s anatomy. However, a massive downside for all 3D processes is the slow, serial nature of fabrication. The majority of 3D printing processes require each layer to be point-by-point scanned in addition to stacking of each individual layer. Tackling the underlying speed-accuracy trade-off, high throughput processes include projection stereolithography and Continuous Liquid Interface Production (CLIP, a new generation of stereolithography). These processes operate via projected UV photopolymerization and layer curing in a single exposure. CLIP and newer “continuous” stereolithography processes further reduce fabrication time by advantageously employing photopolymerization inhibition to eliminate the typical “layer-by-layer” fabrication. These newer fabrication processes are allowing truly rapid fabrication and customization of functional devices. For the technology to become more widely adopted as a viable manufacturing tool, 3D printing must provide end-use products by fabricating more than just complex geometries. Thus, next generation 3D printing technology the next disruptive step in the continuous evolution of 3D printing will require to increase the functionality of the 3D printed parts and components. This work aims to develop high-resolution 3D printing process for direct manufacturing of multi-functional biomedical scaffolds and implants, with emphasis on establishing fundamental understanding of the underlying materials-process-performance relations. Chapter 1 introduces the scientific foundation, from the fundamental light-matter interaction, photopolymerization process, to 3D printing biomedical scaffolds, and ultimately the in-vitro and in-vivo validation. Next, Chapter 2 describes method for on-demand 3D printing biodegradable vascular scaffold (BVS) using citric acid-based biomaterial (B-Ink). Newly developing the speed-working curving method dedicated to the microCLIP process enables more than 100-fold improved fabrication speed to fabricate BVSs with the optimal precision. Chapter 3 describes the necessary further material/mechanical improvements to the bioresorbable vascular scaffolds to be clinically viable. Chapter 3 explorations include creating a nanophase composite of the B-Ink with Poly-L-Lactic Acid (PLLA) and the current attempts to find a maximum concentration of PLLA that is a printable composite. Chapter 4 explores design variation and advantageous use of hydrated material properties to allow in vivo deployment of BVS. Chapter 5 further explores the process to 3D print load-bearing composite scaffold to promote bone healing. We first established the process model to capture the influence of fabrication accuracy using microCLIP involving highly scattered composite resin. The method of multi-materials 4D printing for prompting simultaneous tissue and bone healing is also presented. Finally, Chapter 6 summarizes prospective future research directions of the research noted herein.

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