Real-time monitoring of photoinduced 3D printing through ultrasound

The aim of this thesis work was to initiate a research process aimed at developing a real-time monitoring system for the Digital Light Processing (DLP) 3D printing technology. This moni- toring system is based on the use of longitudinal ultrasonic waves to monitor changes in resin properties during the printing phase. The experiments conducted during this thesis work, which will be detailed in the following chapters, were carried out at the University of Paris-Est Cr ́eteil (UPEC) within the ”Laboratoire Mod ́elisation et Simulation Multi Echelle” (MSME). Photopolymerization, i.e. a chemical process which involves the light-induced solidification of liquid resins, is the core process for DLP technology. This 3D printing method allows the production of solid artifacts from a composition of monomers and/or oligomers, through exposure to UV or visible radiation. Currently, in the commercial landscape, there is a lack of real-time monitoring systems for the polymerization process, which would allow for the timely detection of any defects and the implementation of immediate corrections and an easier calibration of the process. Ultrasound waves are sound waves that have higher frequency than human hearing ability. They are extensively used in the medical field to detect and diagnose internal conditions, includ- ing imaging of internal organs, and to monitor the health and development of the fetus during pregnancy. Beyond the medical world, ultrasound waves can be employed in the industry, for example on a very low power level, to clean and control fragile objects and to ensure that mate- rials are free from defects without the main materials being destroyed. This ability to penetrate opaque materials makes ultrasound waves suitable to many different applications and highly valuable in many sectors. In conclusion, the aim of this thesis has been to introduce ultrasound monitoring techniques within the context of additive manufacturing, laying the groundwork for the future development of this technology.