3D printing has been used extensively in medicine for education, surgical planning, and diagnostic assistance. It has also proven effective for load bearing structural implants, for addressing craniomaxillofacial reconstruction, and airway obstructions. To date, however, there are no clinical examples of additively manufactured soft devices. In this thesis, I will present an approach for the rapid prototyping of a patient-specific left atrial appendage (LAA) occluder via 3D printing and static molding of inflatable silicone/polyurethane balloons. The LAA is a structure known to be highly variable in geometry and the primary source of stroke for patients with atrial fibrillation. I describe the design workflow, fabrication, and deployment of these patient-specific occluders as a proof-of-concept, and show their efficacy using 3D printed anatomic models, in vitro flow loops, and an in vivo large animal model. My work demonstrates the first patient-specific LAA occluder. This occluder could offer a non-pharmacological alternative to current methods, particularly in cases where the morphology causes occlusion to be challenging. Additionally, the design process and manufacturing methods I present could be used in any application where patient-specificity and soft materials are necessary. Proper delivery and deployment of LAA occluders requires exquisite knowledge of spatial orientation in delicate and complex anatomy. While real-time 3D ultrasound offers excellent navigation and interaction with soft-tissues, it requires a high level of expertise and implant materials with distinct ultrasound signatures for proper visualization and orientation. By incorporating sensory feedback into the skin of occluders, it could mitigate the need for complex imaging and expert skills. These skins would provide direct feedback of their degree of inflation as well as contact pressure with surrounding tissues. In my thesis, I will show my work on soft, stretchable sensors that can be directly printed onto pre-fabricated devices via direct ink writing. This printing technique uses two inks—an ionically conductive hydrogel and an electrically insulating silicone—which are patterned and photopolymerized into capacitive sensors. When printed onto a pneumatically actuated haptic device, these sensors enabled the detection of a compressive force of ~2 N, and an internal pressurization of as low as ~ 10 kPa.