Fabrication of PDMS passive micromixer by lost-wax casting

Microfluidic devices have attracted considerable attention for their applicability in disease detection, health care, and environmental monitoring. However, manufacturing at the microscale can be exceedingly difficult, particularly when dealing with devices with an intricate geometry. Most of the manufacturing methods used for microfluidic devices are unable to produce anything more complex than a simple 2.5D structure, which necessitates the bonding of multiple layers to produce a complete 3D structure. This study employs the lost-wax casting method, which is commonly used for the precision casting of metals, in the fabrication of a passive micromixer with two-layer structure using polydimethylsiloxane (PDMS) in a single-step process. The wax pattern was obtained by injection molding, whereupon PDMS was cast in the mold to produce a micromixer after dewaxing. Our results demonstrate the high fidelity of the replication process from the wax pattern to the PDMS micromixer. Furthermore, with the exception of the glass cover, no bonding is required to join multiple layers in the formation of the structure. Compared to other microfabrication methods, such as molding injection and hot embossing, the lost-wax casting method in this study is able to produce microdevices with more complex geometry without the problem of misalignment between bonding layers.