Modeling Dynamic Photobleaching for High-Resolution Digital Light Processing of Enclosed Microchannels

Digital light processing (DLP) bioprinting holds great promise for fabricating functional organ-on-a-chip models and in vitro drug screening platforms. However, existing curing models, largely adapted from synthetic resins, overlook the dynamic photobleaching inherent in hydrogels, leading to poor prediction accuracy for enclosed microchannels. To address this challenge, a custom DLP bioprinting system tailored for high-resolution structure fabrication was developed, along with an optical penetration meter to precisely characterize the light penetration behavior of hydrogel solutions. Based on theoretical derivation and parameter measurement, a dynamic photobleaching compensation curing depth curve (DPC-Curve) was developed, providing accurate prediction and control of single-layer thickness. Guided by this curve, enclosed microchannels with dimensions on the scale of a hundred micrometers were printed directly. As compared to time-consuming trial-and-error, this method is capable of determining key parameters for high-resolution DLP in a theoretical and fast manner. Furthermore, by incorporating anatomical features of human vasculature, biomimetic vascular networks were fabricated with high fidelity. This work provides theoretical insights and technical foundations to overcome current resolution limitations in DLP bioprinting and exhibits potential for the controllable fabrication of vascularized tissues and organs.