Leveraging the third dimension in microfluidic devices using 3D printing: no longer just scratching the surface.

3D printers utilize cutting-edge technologies to create three-dimensional objects and are attractive tools for engineering compact microfluidic platforms with complex architectures for chemical and biochemical analyses. 3D printing's popularity is associated with the freedom of creating intricate designs using inexpensive instrumentation, and these tools can produce miniaturized platforms in minutes, facilitating fabrication scaleup. This work discusses key challenges in producing three-dimensional microfluidic structures using currently available 3D printers, addressing considerations about printer capabilities and software limitations encountered in the design and processing of new architectures. This article further communicates the benefits of using three-dimensional structures, including the ability to scalably produce miniaturized analytical systems and the possibility of combining them with multiple processes, such as mixing, pumping, pre-concentration, and detection. Besides increasing analytical applicability, such three-dimensional architectures are important in the eventual design of commercial devices since they can decrease user interferences and reduce the volume of reagents or samples required, making assays more reliable and rapid. Moreover, this manuscript provides insights into research directions involving 3D-printed microfluidic devices. Finally, this work offers an outlook for future developments to provide and take advantage of 3D microfluidic functionality in 3D printing. Graphical abstract Creating three-dimensional microfluidic structures using 3D printing will enable key advances and novel applications in (bio)chemical analysis.