Research Project Complete

In brief:

Surface topography scans reveal that treatments increase the roughness of the nanochannels, especially fluorine solutions, which on average had a 4nm increase in RMS value in surface roughness.  These conclusions can bedetermined by visual inspection of the images generated from the AFM, where the bumps on the surface appear smoother on the untreated samples compared to the rough edges common to the surfaces of the fluorine treated samples.Therefore, to minimize pressure drop through a nanofluidic system, surface treatments should avoided where flow rate is the primary focus and pressure drop needs to be minimized.

 Force measurement scans with the triangular tip reveal that bromine treatment produces a positive charge buildup that strongly attracts electrical charges, whereas fluorine treatment produces a repulsive force that resisted the cantilever tip.  The same scans ran with the spherical tip indicate that the attraction forces are stronger.  These increases can be attributed to the larger surface area which allows for more charges to build on the tip surface.  The plain surface sample attraction force is stronger than any other force, spherical or triangular tip. 

Information from the MATLAB tells more about the force modulation from the AFM.  Untreated, the charge distribution is virtually identical to the typical models, as expected.  This offers a template to compare the other samples against.  Inspection of the charts created by Excel show that the charges in the bromine treated surface reach far from the substrate surface as indicated by the large Debye lengths. This is consistent to the force curves generated by the AFM software, where the cantilever probe “jumped in” to the surface substrate at a faster rate than any other surface treatments. The fluorine surface has a large concentration of charges near the surface, however, compared to the plain and bromine treated surfaces, the charges are repelling them. For electroosmotic flow, fluorine surface would be optimal despite the rougher surface.Both surface treatments had regressions that appeared to be a combination of both the gold and plain glass surfaces

Here's the link to the full report