Crystal oscillators and methods for fabricating the crystal oscillators are disclosed. Also disclosed are sensors comprising the crystal oscillators, and methods for detecting an analyte using the sensors. In some embodiments, a crystal oscillator can include a convex crystal resonator having a first surface and a second surface, wherein the first surface comprises at least one convex-shaped portion and the second surface is substantially planar; at least one pair of first electrodes disposed on the first surface; and at least one second electrode disposed on the second surface.
