High-Precision and Large-Area 3D Printing of Microfluidic Chips via Digital Light Processing

Digital Light Processing (DLP) technology is renowned for its high precision and efficiency in fabricating intricate microscale structures, making it ideal for applications such as microfluidic chip manufacturing. Despite its advantages, DLP technology faces challenges in achieving optimal UV exposure control, which can lead to printing inaccuracies. Over-curing due to UV energy penetration during the printing of hollow microchannels can cause blockages, and stitching errors in large-area fabrications can degrade precision. These issues limit the effectiveness of DLP 3D printing in the high-precision manufacturing of microfluidic chip molds and chips. This doctoral research focuses on developing a high-precision DLP 3D printing system and optimizing printing processes to improve the accuracy of microfluidic chip fabrication. The study begins with a review of DLP-based microfabrication techniques, assessing commercial DLP printers for resolution and cost, and examining the role of photopolymer resins. It also explores the theoretical foundations of photopolymerization and its application in microfluidic chip production. The research covers five main areas: 1) designing and selecting DLP 3D printing hardware and software; 2) using machine learning to optimize printing parameters for high-precision microfluidic chip molds; 3) introducing a "Spatial-Pixel Integration Compensation (SPIC)" method for accurate, large-scale printing; 4) employing COMSOL simulations to analyze fluid and solid interactions in microfluidic channels; and 5) developing a "sacrificial template" printing process to prevent over-curing. Chapter 2 details the design and construction of the DLP 3D printing system. Chapter 3 presents a machine learning model to predict and minimize printing errors, achieving feature sizes from 20 µm to 200 µm with errors less than 2.3 µm. Chapter 4 integrates the SPIC method into the control system to reduce stitching errors to less than 4 µm, enhancing precision by over 40 times. Chapter 5 uses mathematical modelling and COMSOL simulations to link UV curing dynamics with final chip precision. Chapter 6 introduces a "sacrificial template" process to reduce microchannel height from 291 µm to 20 µm and decrease printing error from 253 µm to 3.5 µm, improving precision by over 70 times. This research demonstrates the potential of DLP 3D printing for high-precision microfabrication. By developing a specialized DLP system and optimizing printing processes, the study achieves direct printing of high-precision microfluidic chip moulds and chips, providing valuable insights for the advancement of micron-scale high-precision manufacturing using UV photopolymerization.