3D Printing of Polymer-Particle Composite Using Electrostatic Deposition and In- Situ Photopolymerization

Polymer-particle composites have been investigated for decades. They have demonstrated wide applications ranging from energy harvesting and storage, biomedical applications, electronics, and environmental sensing to aerospace applications. However, fabricating polymer particle composites with controlled distribution of particles in polymer continues to be a fundamental challenge. As to date, a few additive manufacturing technologies are able to fabricate composites, however, with a limited choice of materials or limited dispersion control. Against this background, this thesis investigates a hybrid polymer-particle composite manufacturing process called Projection based Electro-Stereolithography (PES) process, which integrates electrostatic deposition and projection based stereolithography technologies. In PES, a photoconductive film collects charged particles in the regions illuminated by light. Then collected particles are transferred from the film to a polymer layer with defined patterns. Lastly, a digital mask is used to pattern the light irradiation of the DMD chip, selectively curing the photopolymer liquid resin and particles of that layer. By transferring particles from the photoconductive film to the photopolymer in a projection based stereolithography system, multi- material composites with local controlled dispersions could be produced. A proof-of-concept PES test bed was developed. Various test cases have been performed to verify the feasibility and effectiveness of the developed approach. Challenges in this novel additive manufacturing process, including process design, particle patterning and transferring and polymer-particle curing are addressed in this thesis. It is found that particles can be transferred to a layer of partially cured resin completely and accurately, by using an elastomeric stamping approach. The transferring rate is related to the stamping force applied and degree of curing of the recipient layer. The developed hybrid process can fabricate high resolution polymer-particle composites with arbitrary dispersion patterns, unconstrained print heights and complicated geometries. XIII Although electrostatic deposition process has been investigated as a 3D printing technology for many years, it is the first attempt to integrate it with a projection based stereolithography (SL) process for fabricating multi-material polymer composite components. The novel hybrid process offers unique benefits including local dispersion control, arbitrary filling patterns, a wide range of materials, indefinite printable height and arbitrary complicated geometries