In this article we present the study of the sensitivity optimization of our system of micromechanical characterization called the scanning microdeformation microscope. The flexural contact modes of vibration of the cantilever have been modeled. We discuss the matching between the cantilever stiffness and the contact stiffness which depends on the sample material. In order to obtain the best sensitivity, the stiffnesses must be the closest one to each other. Because the length of the cantilever directly affects its stiffness, the cantilever geometry can be optimized for different materials. We have validated this study with measurements on a soft material the polydimethylsiloxane with a cantilever optimized for materials of Young’s moduli of some megapascals. Experimental results obtained with two different samples have shown the high sensitivity of the method for the measurement of low Young’s moduli and have been compared with nanoindentation and dynamic mechanical analysis results.