Biosensor utilizing a resonator having a functionalized surface

A method for detecting target molecules comprising:

• providing a device comprising a first film bulk acoustic resonator (FBAR), wherein the first FBAR has a first surface functionalized with a first type of biomolecules, wherein the presence of target molecules causes the first type of biomolecules to change the frequency response of the first FBAR;
• exposing the first surface of the first FBAR to a test fluid;
• determining a frequency response of the first FBAR after the first surface has been exposed to the test fluid;
• and
• determining, based upon the frequency response of the first FBAR, whether the test fluid contained target molecules,
• the first FBAR being mounted on a substrate comprising a semiconductive layer and first and second, spaced apart insulating layers, said FBAR having a first edge contacting said first insulating layer and a second edge contacting said second insulating layer, wherein said semiconductive layer, said spaced apart insulating layers, and said FBAR define a void region therebetween;
• wherein the first FBAR except for the first surface, the first and second insulating layers and the semiconductor layer are not exposed to the test fluid, when the first surface is exposed to the test fluid.