Using laws of conservation, a general electro-thermo-elastic 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 piezo-layers and the metallic host material. Several studies of actuation and sensing of single and multi-patch 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 piezo patch 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 step like deformation of the piezo beam. It is envisaged that this concept can be used to develop a switch in a MEMS device. Copyright © 2004 The American Institute of Aeronautics and Astronautics Inc. All rights reserved.