An open-source slicer for 3D mSLA printing of microfluidic chips

Microfluidic chips enable high-precision handling and automation of chemical and biological experiments by transporting and manipulating fluids through complex channel networks embedded on-chip. While polydimethylsiloxane (PDMS) soft lithography remains the standard for microfluidic device fabrication, it is labor-intensive and requires specialized expertise. Masked stereolithography (mSLA) 3D printing offers a rapid, high-resolution alternative, where the 3D chip geometry is fabricated layer-by-layer. These layers are cross-sections of the geometry and stacked on top of each other. However, all existing "off the shelf" slicing processes are optimized for speed and printing outside features rather than the small channels inside microfluidic chips. As a result, the fabrication of these chips still frequently leads to imperfect quality as manifested, e.g., in clogged channels or rough surfaces, which influence the flow through these channels or even render the result unusable. In this work, we propose a novel slicing tool, OpenSLAice, that is optimized for 3D printing of microfluidic chips. To this end, we present a slicing method that automatically detects microfluidic features within a microfluidic chip and, then, orients the chip as well as dynamically slices it so that the imperfections in the fabrication of those features are avoided. It rasterizes the sliced cross-layers and, if several parts should be printed at the same time, it automatically arranges them. Finally, a single print exposure calibration is presented to efficiently determine the required exposure times per layer thickness for resin-printer combinations. The modular, open-source tool is available at https://github.com/cda-tum/mmft-openSLAice and allows to pre-process microfluidic chips for mSLA fabrication.