UC Berkeley

Additive manufacturing has been at the forefront of manufacturing research with advances in basic printing techniques, materials, and post-processing schemes. This work addresses two technical challenges in the broad spectrum of 3D printed structures: (1) functional surfaces and devices; (2) the surface finishing in terms of roughness.

In the first part of this dissertation, a post-fabrication process is investigated to create functional 3D printed structures that can be used for energy harvesting applications by converting mechanical energy to electricity. Chemical vapor deposition (CVD) of various Parylene layers is used to coat a thin film on top of the 3D printed polymer surfaces. The corona discharge method is then used to implant surface charges on the film to construct multi-layered energy harvesting structures. Experimentally, the prototypes can produce 12.5 µW/cm2. Then, a wearable shoe sole energy harvester has been created using 3D printing and CVD of Parylene C and tested in real-life scenarios such as walking, running, and jumping. The system can produce a peak power output of 8 µW/cm2 from a single layer design.

In the second part of this dissertation, a novel surface polishing method has been developed to polish enclosed structures by 3D printed waveguide structures for vacuum electronics for high frequency applications with very stringent surface finish requirements. Magnetic particles have been used in an abrasive slurry and a linear actuator system has been developed to move a magnet. The moving magnetic field can move the slurry inside an enclosed structure to polish the surface. The system has been tested on sample waveguide structures made of copper powders via the electron beam 3D printing process with an initial surface roughness of 40 µm. By using the method developed in this dissertation, the surface roughness has been reduced to reach 1.5 µm in a waveguide.