Take a sneak peek at the new NIST.gov and let us know what you think!
(Please note: some content may not be complete on the beta site.).
NIST Authors in Bold
|Author(s):||Seung Ho Yang; Stephen M. Hsu;|
|Title:||Effect of Colloidal Probe Random Surface Features on Adhesion|
|Abstract:||We have uncovered the fact that colloidal probes often have random surface features which when not properly accounted for, can significantly affect the magnitudes of the measured adhesive forces using atomic force microscopes (AFM). Colloidal probes have been used to measure the pull-off forces between the probe and surfaces. We prepared a series of colloidal probes by attaching glass spheres (radii of 3.3 um to 17.4 um) to the end of AFM cantilevers. Adhesive force between the probes and a silicon wafer surface was measured using an AFM under various loads from 6 nN to 100 nN in dry air. Results showed that the values of the pull-off forces did not correlate with the radii of the probes. Direct imaging of the glass sphere surface using a sharp tip revealed substantial random surface features which altered the size of real contact areas. We extracted the load-bearing areas from the topography data and used them to normalize the adhesion data. The measured adhesive force, after being normalized, was found to be independent of the load and the sphere radii, in agreement with prevailing contact mechanics theory.|
|Conference:||World Tribology Congress|
|Dates:||September 12-16, 2005|
|Keywords:||adhesion,AFM,bearing area,colloidal probe,surface roughness|
|Research Areas:||Characterization, Ceramics|