Abstract
A hybrid micro-nanofluidic channel network is developed on a silicon wafer for bioanalytical applications, such as separation, concentration, and fractionation. The nanochannel is formed on the silicon wafer using surface micromachining techniques, while the microchannel is fabricated on the poly-di-methyl-siloxane utilizing soft lithography techniques. Microfluidic networks not only support the very thin wall of the nanofluidic channel, but also provide appropriate gateways for the fluid/sample flow. The thickness of the microchannels is kept below 10 µm by changing the spin rate and time during photolithography. On the other hand, nanochannel thickness is varied between 100 and 200 nm by controlling the sputtering time of the sacrificial copper layer. Electrochemical wet etching is employed to release the thin layer of copper from the silicon dioxide shell. Our etching technique demonstrates significant advantages over other existing methods, such as wet chemical etching and reactive ion etching, including relatively fast etching rate, good selectivity, less safety and environmental concerns, less monitoring and control issues, and low cost. The dimensions of our microfluidic channels are measured using a profilometer, while the nanochannel thickness is confirmed by the atomic force microscopy and scanning electron microscopy images.
