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.