Physical characteristics such as mass and stiffness of biological objects are emerging as new markers for severe diseases. Micromechanical resonators can be used to quantify multiple of these characteristics simultaneously. In this paper, we propose a methodology that utilizes higher flexural modes of vibration to perform simultaneous characterization of the density and elastic modulus of adsorbates. To demonstrate this concept, a polymeric block with a known dimension and anisotropy is written directly on the cantilever surface using a two-photon polymerization technique and characterised by modal analysis. Our method captures the effective bending stress exerted by non-isotropic materials which is masked in the atomic force microscopy indentation technique.