Gravitational Effects on Optical Lens Fabrication: First Insides on Earth- and Microgravity Experiments

Abstract

Understanding the effects of gravity on manufacturing processes is a pioneering extension of the process parameter space used to date. Until now, the improvement of manufacturing technologies has mainly focused on process parameters such as temperature, pressure, and material composition, as access to variable gravity environments is limited. The Einstein-Elevator opens up new possibilities for the variation of these process parameters and the development of in-space manufacturing technologies. Together with the research of innovative production processes for optical components within the PhoenixD Cluster of Excellence, this creates an entirely new field of research. The research presented here focuses on investigating gravity’s effects on dispensed optical lens production. Using a jet dispenser, sessile droplets are produced during a flight phase in the Einstein-Elevator and cured directly by UV polymerization. As part of this study, optical lenses were produced and compared under microgravity and Earth’s gravitational conditions. Geometric properties such as height and contact angle of the lenses produced were analyzed. It was found that lenses fabricated under microgravity have a larger contact angle than those fabricated under Earth gravity. Similarly, the height increases with decreasing gravity. These results are consistent with the theoretical assumptions described, although generalized theories to describe the morphology of a sessile droplet are not yet available. The case study findings on the influence of gravity as a process parameter on drop morphology represent a fundamental improvement for additive manufacturing technologies, especially for in-space manufacturing.