Abstract: Multi-layer structures with functionalities, varying height channels, complex microfluidic structures like valves, mixers and high aspect ratio channels (hereby referred as 3D-Microfluidics) are very difficult to fabricate using conventional microfluidics fabrication methods. On the other hand, high geometric complexity, less manufacturing time, low cost, multiple material options, improved mechanical properties and dimensional accuracy have made 3D printing a very popular technology for macroscale manufacturing. The resolution and accuracy of state-of-the-art 3D printers are well established on micro-scale with a potential for nanoscale. The 3D printing process is additive in nature and can produce intricate 3-dimensional (3D) shapes and structures in micrometer range, with a few specialized printers claiming to have accuracy down to 500 nm. Due to its ability to print intricate 3D shapes in very small dimensions with high accuracy, 3D printing is considered as a strong alternative technique to fabricate complex and difficult to manufacture 3D Microelectromechanical Systems (MEMS) and 3D-Microfluidic devices. This paper discusses the brief history as well as current challenges and limitations of conventional 3D-Microfluidics fabrication techniques and elaborates the research progress reported in the last years related to 3D printing of 3D-Microfluidics. The discussion includes a critical analysis of the state-of-the-art and presents challenges that are yet to be addressed to successfully broaden the use of this novel technique for the aforementioned devices. A case study is also presented to analyze the potential use of desktop 3D printers for fabrication of 3D-Microfluidics for lab-on-a-chip and other applications. Finally, future trends of 3D printed 3D-Microfluidic devices are discussed.
Keywords: 3D printing, 3D-Microfluidics, Additive Manufacturing, Design Issues, Design for Additive Manufacturing
