Glaucoma is a disease that affects tens of millions of people around the world. The development of MEMS and the generation of new materials allow the development of implantable micro-devices with improved biocompatibility. The knowledge of biomolecules associated with the glaucoma pathology will increase the effectiveness of a microvalve for glaucoma tretmentt. In this sense, a mass microsensor capable of sensing biomolecules is desirable. This book was focused on the design, simulation, fabrication and characterization of MEMS-based mass microsensors for the detection of biomolecules. Regarding the biocompatibility, UNCD and Parylene were used as structural materials; as piezoelectric materials, quartz, PVDF and AlN were used. The parameters of the resonators were extracted by using 3D FEM models and experimental results. UNCD films used as substrate, yielded a highly oriented (002) AlN films even as thin as 80 nm; it exhibited a piezoelectric coefficient of about 5.3 pm/V, one of the highest demonstrated today. AlN/diamond structure is a very promising device for FBAR applications so it opens a huge field of biomedical applications.