Nanometer-scale fluidic structures have gained considerable attention in the last few years, because they provide unique capability in biomolecular manipulation and control. Nanofluidic structures with a critical size smaller than 100 nm can put a physical constraint on the biomolecules in solution, therefore controlling the molecules in a unique and useful way. For nanofluidic applications, one critical issue is the availability of reliable, reproducible fabrication strategies for nanometer-sized structures. In this research, we conduct the full experimental characterization of planar nanochannel fabrication using standard photolithography and wafer bonding techniques (anodic bonding and glass-glass fusion bonding), without resorting to the complex, expensive nanolithography and/or thin film deposition techniques.

We have demonstrated that nanofluidic channels, as thin as 20 nm with low aspect ratio of 0.004 (depth to width) on silicon substrate and 25 nm with aspect ratio of 0.0005 on glass substrate, can be achieved with anodic bonding and developed glass-glass bonding technique, respectively, as shown in Figure 1. The thickness uniformity of sealed nanofluidic channels are confirmed by the cross-sectional SEM analysis after bonding. Such a uniform, flat nanofluidic channel can be used for more careful, controlled study of molecular and fluidic transport in nanopores or confined space. This result will be useful in designing next-generation nanofluidic devices that can be used for protein separation and biomolecule preconcentration.

Figure 1 Cross-sectional SEM images of nanofluidic channels. (Left) 25 nm deep channel made by glass-glass bonding. (Right) 20 nm deep channel made by silicon-glass anodic bonding.

References

1. Mao, P. "Fabrication and characterization of nanofluidic channels for studying molecular dynamics in confined environments," S.M., Massachusetts Institute of Technology, Cambridge, MA (2005).
2. Mao, P. & Han, J. "Fabrication and characterization of 20 nm nanofluidic channels by glass-glass and glass-silicon bonding," Lab on a Chip 5, 837-844 (2005).