Diffusion-induced beam bending in hydrogen sensors

The diffusion-induced bending of both single-layer and bilayer beam structure is analyzed by using linear elastic beam theory and the Moutier theorem. A closed form solution of the radius of curvature due to diffusion is obtained. For the single-layer beam structure, the radius of curvature is inversely proportional to the bending moment created by nonuniform concentration distribution. For the bilayer beam structure, the curvature is a linear function of the mismatch strain between the two layers and the bending moment introduced by diffusion. The mismatch strain depends on the concentration and the partial molar volume of the diffusing component in both layers. Application to microelectromechanical systems hydrogen. sensors with a layer of Pd is shown. (C) 2003 American Institute of Physics.