High-accuracy DLP 3D printing of closed microfluidic channels based on a mask option strategy

Microfluidics is a crucial technology in biological and medical fields, and its traditional fabrication methods include soft photolithography poly(dimethyl siloxane) (PDMS) technology and polymethyl methacrylate (PMMA) injection moulding technology. However, these techniques face challenges in manual alignment and bonding issues when they are used to manufacture microfluidic chips with complex flow channels. To overcome these limitations, digital light processor (DLP) 3D printing technology has been proposed as a promising alternative. However, this method is prone to problems such as channel blockage or shape distortion caused by the optical proximity effect or curing light transmission during the manufacture of microfluidic chips with small-diameter channels. This paper introduces a method to enhance the manufacturing technology by controlling the local greyscale of the projection image during DLP 3D printing. This allows for modulation of the curing light intensity, thus reducing the optical proximity effect and the impact of transmitted light on extra areas. The methodology can be employed in the production of microfluidic devices with circular and square apertures in the microchannels, utilizing commercially accessible general-purpose resins that are readily available in the market. The printed microfluidic devices show improved quality, with a channel size that closely matches the preset size, in contrast to significant channel blockage in devices printed without greyscale optimization. This method provides a new approach for enhancing the quality of low-cost microfluidic chip production and improves the print quality based on the resolution of the printer and resin used.