3D printing of optical components via free-radical frontal polymerization

Abstract

Optical manufacturing is often a process dictated by high-cost machinery and long working times. In this thesis we examine the benefits and drawbacks of the different optical manufacturing technologies, and introduce 3D printing as an alternative approach. Towards this end we present a methodology towards creating freeform optical components via grayscale digital light projection (DLP) frontal polymerization. We present an instrument which can be created cheaply, offer experimental validation of its functionality, and detail the driving algorithms involved. Furthermore, as the nature of our system lends itself well to analyze the curing characteristics of various photoactive compounds, we extensively characterize several free-radical photopolymers in a deoxygenated environment in terms of their curing characteristics as a function of irradiance, cure time, and photoinitiator concentration. We find that the photoresins do not follow the Bunsen-Roscoe reciprocity law for photochemistry, and offer quasiempirical explanations in terms of evolution of the reaction rate constants at constant degree of cure. Finally, we use the designed system to produce optical components and analyze them in terms of their surface quality and form replication, elucidating towards the limiting bounds of this technique.