Identification of the electro-elastic coupling from full multi-physical fields measured at the micrometer scale
Résumé
Metal coated micro-cantilevers are used as transducers of their electrochemical environment. Using the metallic layer of these cantilevers as a working electrode allows one to modify the electro-chemical state of the cantilever surface. Since the mechanical behavior of micrometer scale objects is significantly surface-driven, this environment modification induces bending of the cantilever. Using a full-field interferometric measurement set-up to monitor the objects then provides an optical phase map, which is found to originate from both electro-chemical and mechanical effects. The scaling of the electro-chemically-induced phase with respect to the surface charge density is modeled according to Gouy-Chapman-Stern theory, whereas the relationship between the mechanical effect and the surface charge density is analyzed. An identification technique is described to determine a modeling of the electro-elastic coupling and to identify the spatial charge density distribution from full-field phase measurements. Minimizing the least-squares gap between the measured phase and a statically admissible phase field, the mechanical effect is found to be charge-driven. The charge density field is also found to be singular on the cantilever edge, and the shear stress vs. charge density is found to be non-linear.
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