Enhancing the Polymeric Landscape for 3D Printing Using Post-Fabrication and Supramolecular Design
Berry, Danielle R
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Additive manufacturing, also known as 3D printing, is a process of materials fabrication assisted by computer aided design (CAD) to form three-dimensional objects with complex geometry. Many 3D printing techniques have been developed since the inception of the process, with three of the most popular and affordable being Fused Deposition Modeling (FDM), Stereolithography (SLA) and Direct-Ink Writing (DIW). While 3D printing has many advantages, it is plagued with limitations such as poor interlayer adhesion, limited resolution, rough surface finish, limited mechanical properties of printed parts, and limited compatible materials. For these reasons, 3D printing has been mainly limited to prototyping and has not been adapted for mass production manufacturing. To address the limitations associated with 3D printed objects, we have developed several techniques and formulations to improve the performance and broaden the applications of 3D printed materials. To address the poor resolution associated with FDM printing, we have employed a base hydrolysis reaction of the common 3D printing filament polylactic acid. We demonstrated how printed microneedle arrays could be “chemically etched” with a potassium hydroxide solution to the appropriate dimensions for applications as transdermal drug delivery devices. To address mechanical strength, we introduced a cost effective, biopolymer-based hydrogel for applications in water purification fabricated via DIW. It was demonstrated that the addition of chitosan to a commercially available shear-thinning polymer resulted in an increase in Young’s modulus as well as functionality capable of chelating toxic heavy metals, which was enhanced by increased surface area only achievable through 3D printing. We have also shown how post-fabrication of hydrogels can be achieved through base catalyzed thiol-Michael click chemistry, which in contrast to traditional radical crosslinking methods, allowed for tuning the of mechanical properties through the use of various crosslinkers and also enhanced degradation, a feature of the thiol/acrylate Michael addition adduct. Lastly, we aimed to address limitations in available materials by developing a facile method of synthesizing slide-ring gel materials through a catalyst-free thiol-Michael addition, which resulted in a stretchable gel material. We hope to further characterize and adapt this method to be compatible with the EMB3D 3D printing process. Chapter 1 provides and introduction to available 3D printing techniques, previous methods of addressing limitations associated with 3D printing, and a background on new materials and potential materials for 3D printing. Chapter 2 describes our advances in 3D printing through the development of chemical etching methods for the fabrication of biodegradable 3D printed microneedles for transdermal drug delivery, and the formulation and fabrication of a biopolymer-based hydrogel for toxic heavy metal absorption from water. Chapter 3 describes chemical methods for 3D printing through a radical free post-fabrication method of crosslinking hydrogels in solution through a based catalyzed thiol-Michael addition. Chapter 4 describes potential new materials for 3D printing through the fabrication of slide-ring gel materials using a “one-pot” synthetic approach, with the end goal of adapting the system for EMB3D 3D printing.