Direct Deposition of Bio- and Nanomaterials by Nanofountain ProbeAndrea Ho, M.Sc., Northwestern University, 2007.
Major Professor: Dr. Horacio D. Espinosa.
A third generation of the nanofountain probe (NFP) was microfabricated. Improvements in the processing resulted in a more robust device capable of directly delivering larger biomolecules and nanomaterials. As with the previous generations, the unique feature of this NFP is its volcano-like apertured probes consisting of a core tip surrounded by an outer shell.
Simulations of fluid flow through the NFP were conducted, and confirmed that liquid could flow via capillary action through the microchannels to the probe tips, while remaining confined to the core tip area of the probe. Thus high resolution patterns could be written by the NFP.
An analysis of the diffusion mechanism of gold nanoparticles on a substrate was elucidated. It was determined that nanoparticle dot growth is much slower than in a surface diffusion model, and that the formation of filled and hollow dot features can be explained by an annular diffusion model.
Improved DNA dot arrays were patterned with the new NFP, as compared to previous patterns made with the second generation probes. The features were successfully hybridized, confirming the preservation of their biological activity. With an applied electric field, bovine serum albumin and IgG proteins were deposited in dot and line patterns. The relative humidity effects on the current-voltage characteristics during deposition may ultimately affect the pattern resolution. Due to higher resistance through the NFP with the use of water-based inks, gold nanoparticles and proteins in DI water could not be deposited under an electric field. Lastly, preliminary patterns of cobalt ferrite sol were also made on silicon, silicon nitride and gold substrates.