Microfabrication of Rapid Micro-Moulds for Microfluidics Combining Additive Manufacturing and a Custom Ultraviolet-LED Photolithography Tool

Fabrication of mould inserts using additive manufacturing (AM) or 3D-printing is generalised as rapid-tooling and offers great design flexibility and potential for rapid prototyping using injection and micro-injection moulding. In miniature scales, established additive manufacturing methods such as material jetting and stereolithography usually suffers from surface quality defects and lack of sufficient precision and accuracy for true-microscale moulds 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 planarised rapid-tools for microfluidic applications. The planarisation 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 planarised inserts, using non-contact and contact modes. The process repeatability was characterised by varying revolutions per minute (RPM) and laser-scanning confocal microscopy of key dimensional features. The results showed that higher RPM values are favourable for obtaining better surface quality and repeatability. Obtained micro-features were compared with directly-printed micro-features using a material jetting printer and significant improvements were reported in the repeatability of surface roughness metrics, with up to 50% lower coefficient of variations. This novel process offers a viable method for creating highly precise and accurate prototyping moulds and is expected to be impactful for the accelerated iterations of microfluidic devices.