Using laws of conservation, a general electrothermoelastic formulation has been developed for the analysis of smart structures. Based on this formulation a layer-by-layer finite element model has been developed using variational principle. It is shown that the layer-by-layer finite element modeling effectively captures the continuity of shear stress across the interface between piezolayers and the metallic host material. Several studies of actuation and sensing of single and multipatch smart beams have been carried out. The key difference between actuation and sensing has been brought out with regard to the variation of shear stress along the span at interfaces between piezopatch and the core. In addition, the influence of electric field along the span of a piezo cantilever beam has been studied, and it is shown that this electric field produces a large transverse shear stress resulting in a steplike deformation of the piezobeam. It is envisaged that this concept can be used to develop a switch in a microelectromechanical-system device. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.