Some embodiments relate to method of fabricating a sensor. The method includes providing a substrate wafer that includes a suspended beam; adding an adhesive layer to the substrate wafer such that the adhesive layer covers portions of the substrate without covering the suspended beam; positioning a cover wafer onto the adhesive layer such that the suspend beam is exposed to ambient air through openings in the cover wafer; and functionalizing the suspended beam by contacting the suspended beam with materials through the opening in the cover wafer.