In this paper, a new model of piezoelectric cantilever is developed, it can be heavily used in a micro electromechanical system (MEMS). This new prototype eliminates several risks caused by the previous means already used and increases the sensation in terms of rheology. Our approach is based on the approximation of the Eigen frequency shift when the micro-beam is totally immerged in an incompressible fluid. The density variation of the fluid is deduced and solved according to the behavior of the Eigen frequency. The material used for the manufacturing of the cantilever beam is Silicon Dioxide or Silica which is a porous material. Moreover, if the fluid contains particles, they can be adsorbed on the pores of the micro-beam and cause a change in the mass. Examination of theoretical computation by simulation approach was done using COMSOL Multiphysics software. The self-sensing micro-cantilever obtained in vacuum is around 390 Hz/ng measured at a center frequency of 960 kHz and with a density resolution of 0.055 % in fluid measured at a center frequency of 680 kHz. The used cantilever has the dimensions of (400 × 140 × 10) µm³.