Microfabrication of Rapid Micro-Molds for Microfluidics Combining Additive Manufacturing and a Custom Ultraviolet-Light-Emitting Diode Photolithography Tool

Abstract Fabrication of mold inserts using additive manufacturing (AM) or 3D-printing is generalized as rapid-tooling (RT) and offers great design flexibility and potential for rapid prototyping using injection and micro-injection molding. In miniature scales, established AM methods such as material jetting and stereolithography usually suffer from surface quality defects, lack of sufficient precision and accuracy for true-microscale molds and components. Current work demonstrates a process chain where material jetting and ultraviolet light-emitting diode (UV-LED) photolithography are combined to create precise and accurate microstructures on 3D-printed and planarized RTs for microfluidic applications. The planarization step involved spin-coating with 3D-printed resins to obtain a flat surface, followed by a custom-made UV-LED mask lithography step for inducing microchannels on the planarized inserts, using noncontact and contact modes. The process repeatability was characterized by varying revolutions per minute (RPM) and laser-scanning confocal microscopy of key dimensional features. The results showed that higher RPM values are favorable for obtaining better surface quality and repeatability. Obtained microfeatures were compared with directly-printed microfeatures using a material jetting printer and significant improvements were reported in the repeatability of surface roughness metrics, with up to 50% lower coefficients of variation. This novel process offers a viable method for creating highly precise and accurate prototyping molds and is expected to be impactful for the accelerated iterations of microfluidic devices.