The research objective of this award is to test the hypotheses that 1) an interferometery-based sensor can monitor the extent of polymerization throughout the irradiation area of a photopolymerization-based additive manufacturing process, 2) the sensor will enable measurement of cured part size, and 3) the sensor will enable feedback control of the process. Most additive manufacturing processes operate in an open-loop manner. In contrast, a novel interferometry-based sensor is investigated to monitor photopolymerization processes in real-time. The sensor will be integrated with a research Exposure Controlled Projection Lithography system to enable part fabrication. With this sensor, high resolution interrogation of polymerizing samples can be performed, enabling an understanding of the spatial and temporal distribution of polymerization rate and degree of cure as a function of process variables. A new model of photopolymerization will be tested that incorporates polymerization rate, inhibitor presence and diffusion, and shrinkage. The model will be used in the development of a new approach to process planning and to predict cured part size and shape. Feedback control capability will be developed that enables adjustments of photopolymerization extents in order to improve process precision and repeatability.
If successful, this research could benefit society by enabling the manufacture of precision micro-optics devices that could not be fabricated economically by conventional processes. These devices could have applications in medical imaging, portable energy, photography, and metrology industries, among others. Graduate and undergraduate students from under-represented groups will be recruited for this project. The work will enhance the infrastructure for research and education by developing and maintaining facilities for photopolymerization sensing and control experiments and for part fabrication. Broad dissemination will be achieved through courses enhanced with research results, undergraduate research opportunities, active industry involvement, papers and presentations in engineering forums, and a web-site to report results and provide access to the developed additive manufacturing sensing and control system.
