Current and emerging trends in polymeric 3D printed microfluidic devices

During the last two decades, 3D printing technology has emerged as a valid alternative for producing microfluidic devices. 3D printing introduces new strategies to obtain high precision microfluidic parts without complex tooling and equipment, making the production of microfluidic devices cheaper, faster, and easier than conventional fabrication methods such as soft lithography. Among the main 3D techniques used for this purpose, fused filament manufacturing (FFF), inkjet 3D printing (i3Dp) and vat polymerization (VP) are of the greatest interest since they are well-established techniques in the field and are cost-affordable both in equipment and material. However, there are still some barriers in terms of technology and materials to overtake for definitively establishing 3D printing as a truly microfluidic production method. For example, the level of resolution and precision of 3D printed microfluidic parts still does not reach the level of conventional fabrication techniques, and, from a materialistic point of view, few materials present the desired characteristics (e.g., biocompatibility, optical transparency, and mechanical properties) for target areas such as medicine, analytical chemistry, and pharmaceuticals. This review intends to evaluate and analyze the current state of polymeric 3D printing techniques and materials to manufacture microfluidic chips. The article will show and discuss the latest innovations, materials, and applications of such 3D printed microstructures. The focus of this review is to provide an overview of recent and future developments in 3D printing and materials in the branch of microfluidics fabrications, showing that the selection of the right materials together with the design freedom afforded by 3D printing will be the cornerstone for microfluidic development.