Rapid assembly of multilayer microfluidic structures via 3D-printed transfer molding and bonding

A critical feature of state-of-the-art microfluidic technologies is the ability to fabricate multilayer structures without relying on the expensive equipment and facilities required by soft lithography-defined processes. Here, three-dimensional (3D) printed polymer molds are used to construct multilayer poly(dimethylsiloxane) (PDMS) devices by employing unique molding, bonding, alignment, and rapid assembly processes. Specifically, a novel single-layer, two-sided molding method is developed to realize two channel levels, non-planar membranes/valves, vertical interconnects (vias) between channel levels, and integrated inlet/outlet ports for fast linkages to external fluidic systems. As a demonstration, a single-layer membrane microvalve is constructed and tested by applying various gate pressures under parametric variation of source pressure, illustrating a high degree of flow rate control. In addition, multilayer structures are fabricated through an intralayer bonding procedure that uses custom 3D-printed stamps to selectively apply uncured liquid PDMS adhesive only to bonding interfaces without clogging fluidic channels. Using integrated alignment marks to accurately position both stamps and individual layers, this technique is demonstrated by rapidly assembling a six-layer microfluidic device. By combining the versatility of 3D printing while retaining the favorable mechanical and biological properties of PDMS, this work can potentially open up a new class of manufacturing techniques for multilayer microfluidic systems. Microfluidics: Multilayered devices through rapid 3D printing A 3D printing technique for fabricating multilayered microfluidic devices promises to overcome the limitations of conventional fabrication. Advances in microfluidic technology are proving invaluable for disease diagnosis, DNA analysis, and drug discovery, but lithography-based device construction is time-consuming, reliant on costly infrastructure, and restricted to rectangular features. To address these limitations, Casey Glick at the University of California, Berkeley, United States, and his colleagues developed a versatile 3D printed transfer molding technique enabling them to mold flexible polymers into arbitrary configurations, such as thin membranes and controllable microvalves. They also rapidly assembled multiple layers into a single device; by using custom alignment marks and 3D printed stamps, they selectively applied adhesives without clogging the hair-width microflu