Printing depth modeling, printing process quantification and quick-decision of printing parameters in micro-vat polymerization

Vat photopolymerization is a widely employed additive manufacturing (AM) technique that commonly applying a digital light processing (DLP) light engine to provide a patterned light source. Notably, printing extreme-size structures is challenging, and the selection of printing parameters was currently highly reliant on repeatable trial-and-error experiments. In this work, a theoretical model for curing depth prediction was established by observing the effect of light intensity. A correction factor n was introduced to optimize the relationship among the critical curing energy, exposure time, and light intensity. Forming experiments verified the accuracy of the proposed theoretical curing depth prediction model, and a correction factor n equal to 0.75 was obtained. Optical rheological characterization experiments and Fourier transform infrared spectroscopy (FTIR) supported the quantitative characterization of the DLP printing process while revealing a stepwise transition during photocuring. Finally, a guidance for quick selection of the optimal curing time for 3D structure was obtained and applied to the high-precision microstructure printing process. High-fidelity microneedle arrays with 12 μm details were printed. This method of rapid selection of printing parameters and printing microstructures with high-precision details can potentially be used in the field of 3D bioprinting.