Castable 3D monolithic microfluidic devices

Microfluidic devices remain difficult to translate into commercial products, particularly for three-dimensional (3D) applications. While soft lithography offers high-resolution features and biocompatibility, its workflows and planar geometries are limited. Conversely, industry-standard injection moulding enables scalability, but lacks flexibility and incurs high upfront costs. Here, we present an innovative hybrid microfabrication methodology combining stereolithographic 3D printed moulds with flexible wire templating and polydimethylsiloxane (PDMS) casting to create monolithic 3D microfluidic devices. Leveraging injection moulding design principles, this enables the rapid and repeatable fabrication of microfluidic devices with embedded internal channels, variable-height membranes, and curved geometries. Our methodology is validated using a variety of devices, including flexible membranes, plug-based flow distributors for 96-well plates, and high-aspect-ratio bioreactors with integrated electrodes. The resulting devices were leak-proof, reusable, and compatible with standard cell culture systems. This scalable, low-cost methodology retains the advantages of PDMS while allowing for 3D design freedom for both internal channels and external features, making it ideal for emerging applications such as organ-on-chip, bioprinting, diagnostics, and soft robotics.