Adsorption-Induced Cantilever Bending

One of the most significant aspects of the cantilever sensor is that the adsorption-induced cantilever bending is not affected by operation in solution. We were able to detect the Cs ion at concentrations as small as 10 M in solution using the cantilever deflection method. This corresponds to a coverage of 4 X 10" monolayers ... 

Therefore, the deflection of the cantilever is directly proportional to the adsorption-induced differential surface stress. Surface stress has units of N/m or J/m2. Equation (12.3) shows a linear relation between cantilever bending and differential surface stress. 

The mechanism for cantilever bending is assumed to be adsorption-induced stress. The adsorption decreases the surface free energy and surface free energy is density is surface stress. It is speculated that the hydrogen bonding between the nitro groups of the explosives molecules and the hydroxyl group of 4-MBA is responsible for the easily reversible adsorption of explosive vapours on the SAM-coated top surface of the cantilever. This... 

In section 4.4.9 experimental data changes of surface stress induced by the adsorption of gases, alkali metals, semiconductors and metals on single crystal surfaces are compiled from cantilever bending experiments. 

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