Chemomechanical actuation of a microcantilever beam induced by biomolecular binding such as DNA hybridization and antibody-antigen binding is an important principle useful in biosensing applications. As the magnitude of the forces involved is very small, increasing the sensitivity of the microcantilever beams involved is a priority. In this paper we are considering to achieve this by structural variation of the cantilevers. Merely decreasing the thickness of the microcantilever may improve the sensitivity, but it gives rise to the disadvantages of 'arching' and lesser reliability due to greater probability of defects during fabrication. We consider a 'ribbed' cantilever that eliminates the disadvantages while improving the sensitivity simultaneously. Simulations for validation have been performed using the finite element analysis software ANSYS 8.0. The simulations reveal that a ribbed microcantilever is almost as sensitive as a thin cantilever and has relatively very low arching effect. Simulations also reveal that higher the arching lower is the sensitivity.