Nanomechanics of a self-assembled monolayer on microcantilever sensors measured by a multiple-point deflection technique

A multiple-point deflection technique has been used to investigate stress evolution during the adsorption of thiolated DNA oligomers and dodecanethiols on microcantilever sensors in the liquid phase. The adsorption-induced bending of the cantilever was measured by focusing eight light-emitting diodes on equidistant positions along the length of a gold-coated silicon cantilever using optical fibers. The deflection at each point on the cantilever was measured to determine the curvature of the cantilever. While the compressive stress uniformly increased to equilibrium during the adsorption of the thiolated DNA oligomers, the stress increased abnormally during the adsorption of the dodecanethiols, which are known to form a denser monolayer compared with thiolated DNA oligomers. This nanomechanical measurement has a great potential for investigating complete surface stress profiles with high resolution during adsorption processes.