Surface Mechanics and Full-Field Measurements: Investigation of the Electro-Elastic Coupling

Abstract

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. On the other hand, describing the involved surface effects in the continuum mechanics framework is still challenging. Several attempts to overcome the Stoney’s surface stress failure to satisfy field equations tend to show such a description has to be non-local, so that at least one ‘characteristic length’ parameter has to be used. The consequence is twofold: first, suited modelings have to be developed to describe the surface effects at the cantilever scale; and second, the involved characteristic length is (thermodynamically) connected to the molecular mechanisms at the cantilever surface, and may therefore be a key parameter for the target molecules identification. This requires to experimentally access displacement fields induced by the molecular interactions under scrutiny. A set-up providing mechanical and chemical fields along the cantilever is thus implemented focusing on cases where the cantilever’s surface reacts heterogeneously. The large amount of data obtained using full-field set-ups is redundant from the mechanical point-of-view, and this redundancy is used to identify some of the key parameters describing the mechanical surface effects. Results obtained when studying the electro-elastic coupling in a non-adsorbing case are presented.