UC Davis

The emergence of 3D printing has revolutionized the world of manufacturing through its ability to enable production of parts with unparalleled geometric complexity and functionality. While the list of materials (e.g. polymers, ceramics, metals) compatible with 3D printing workflows grows steadily, multi-material printing has proved challenging, with existing strategies for mixing materials prone to introducing defects to the printed part (e.g. during nozzle swapping) or requiring robust electromechanical control systems to be in place that can be prohibitively costly. At the same time, microfluidics has been shown in the literature to excel at handling different material flow stream whether for mixing or swapping of multiple materials. With numerous studies over the past two decades thoroughly describing the physics of sub-millimeter flows along with various experimental setups for different applications (e.g. emulsification/droplet production, material synthesis), microfluidics technology is well-positioned to assist researchers in enabling new multi-material 3D printing workflows and applications.

This dissertation is a compilation of works demonstrating the adoption of microfluidic technologies and principles to enable multi-material 3D printing processes and novel applications in the areas of functional printing and tissue engineering. First, glass capillary microfluidic devices were adapted for use as printheads in a novel droplet-based 3D printing technique that allows for programmable tuning of printed object local properties through the inclusion of droplets at select points. Soft robotic grippers that respond to an external B-field and bend at select points were designed and printed to demonstrate the utility of this droplet-based 3D printing technique. Second, a multimaterial bioprinting workflow involving Matrigel bioink core within an agarose shell was developed to enable the enhancement of in vitro intestinal epithelium growth and tissue organization. These works showcase the continuing trend of exploiting the unparalleled spatiotemporal control of materials offered by microfluidics to facilitate multi-material 3D printing strategies and thereby contribute to the emerging body of knowledge on the matter.