A composite, analyte sensor includes a substrate; a micro- or nano-electro-mechanical (MEMS; NEMS) resonator that is coupled to the substrate at least two edge locations (i.e., it is at least doubly-clamped) of the resonator, wherein the resonator is in a statically-buckled state near a buckling transition point of the resonator; and a chemically-responsive substance covering at least a portion of the surface of the resonator that will undergo a conformational change upon exposure to a given analyte. The resonator may be a double-clamped, statically-buckled beam (or bridge), a multiply-clamped, statically-buckled dome (or crater), or other resonator geometry. The sensor may include two or more at least double-clamped, statically-buckled, composite MEMS or NEMS resonators each operating near a buckling transition point of the respective resonator, and each characterized by a different resonant frequency. A method for sensing an analyte in ambient air.