Charge redistribution in electrochemically-actuated mechanical sensors

Many proofs of concept studies have established the mechanical sensitivity of functionalized microcantilevers to a large spectrum of target molecules. However, moving to real-life applications also requires the monitored mechanical effect to be highly specific. Moving towards more specificity in cantilever-based sensing, monitoring the mechanical response of electrochemically actuated microcantilevers is then thought to provide a fast, reliable and complementary experimental information to the longtime cantilever bending measurement for the detection of target molecules. Full-field measurements are therefore used to investigate the way the electro-elastic coupling is altered when a microcantilever undergoes decane-thiol adsorption. The proposed technique reveals that the latter results in a charge density redistribution along the cantilever in addition to the local surface passivation. Focusing on the cantilever tip displacement under electrochemical actuation, this redistribution partially compensates the electro-elastic coupling alteration due to the surface passivation, therefore possibly yielding an ambiguous detection result. This effect should be taken into account for the optimal design of specific electrochemically actuated mechanical sensors.