Theoretical prediction and experimental validation of the digital light processing (DLP) working curve for photocurable materials

Abstract

Abstract To achieve high-precision printing results in the digital light process (DLP), the Jacobs working curve (the relationship between the absorbed UV light energy and the cured thickness of the photocurable material during UV light exposure) is of great importance in obtaining accurate printing parameters for a particular photocurable material. However, conventional experimental measurements of the variation of cured thickness under UV light exposure for each individual photocurable material are extremely time-consuming and wasteful of material. In this current research, an analytical model based on differential analysis is developed to analytically obtain the relationship between UV light exposure time and the cured thickness of a single layer. In this model, the analytical Jacobs working curve can be described as depending only on three physical properties of photocurable materials: solid absorbance, liquid absorbance, and gelation time. Moreover, adjusting the concentration of UV absorber in the photocurable materials leads to a good agreement between the analytical Jacobs working curve and the experimental data. The analytical Jacobs working curves of polyethylene (glycol) diacrylate (PEGDA) hydrogel and gelatin methacrylate (GelMA)/decellularized extracellular matrix (dECM) bioink were utilized to predict DLP printing parameters, which were demonstrated to be accurate enough to print 3D complex structures, i.e., three periodic minimal surfaces (TPMS), a triangle cone, and a diamond grid overlaid spherical shell. This theoretical model of the DLP Jacobs working curve lays the foundations for appropriate DLP printing parameters, and in particular makes possible high-precision DLP printing of photocurable materials.