Novel monolithic and multilevel integration of high-precision 3-D microfluidic components

A novel fabrication process has been devised for monolithic integration of multilevel passive microfluidic components, which are channel, reservoir and orifices, as a single body. These components are precisely defined by single-step 3-D photolithography followed by single-step electroplating. This single-step fabrication of the components is possible by forming the three-dimensional (3-D) photoresist mold, which has channel and reservoir parts in the lower layer and an orifice part in the upper layer. We obtain this multilevel photoresist mold using multiple exposures with varying exposure depths, followed by a single development step, which realizes the 3-D latent image of the unexposed volume in the photoresist. By merely repeating these processes, we have easily fabricated single-body two-level microfluidic components. The microfluidic channels can cross each other on a different level and microfluid in different levels can join through the first-level orifices (microfluidic via). Two outmost orifices can be used as both inlet and outlet. These multilevel structures are similar to multilevel interconnection in VLSI. This process is easy, simple, and compatible to integrated circuit (IC) process owing to low process temperature (<120°C) and the monolithic feature. Additionally, this single-body fabrication improves a process yield and reliability of the components very much.