Fabrication of integrated microfluidic devices by direct ink writing (DIW) 3D printing

This paper describes a simple method to apply 3D printing to fabricate microfluidic devices integrated with fluid handling and functional components. We used a direct ink writing (DIW) 3D printer to dispense a fast-curing flexible silicone resin on various substrates to form microchannels. The dispensed silicone was interfaced with another flat substrate to form microchannels with tunable dimensions. Using this method, we fabricated channels with dimensions as small as 32 μm in width and 30 μm height. We fabricated basic microfluidic modalities (e.g. straight and branched channels, mixers, chambers and droplet generators) as well as functional modalities (e.g. valves, variable flow resistors and gradient generators) on an optically transparent substrate. The method can be readily extended to fabricate microchannels on a diverse range of functional substrates. We showcased this capability by fabricating microchannels on an unmodified printed-circuit board (PCB) to form the interface between the fluid and the electric circuits, and microporous membranes to perform air-liquid human keratinocyte cell culture. Our approach has enabled rapid prototyping of microfluidic devices integrated with functional components required for lab-on-a-chip applications, complementing current approaches in 3D printed microfluidics that are restricted in attainable dimensions and available materials.