Embodiments of the present invention provide a sensor comprising a sensor resonator member configured to resonate at a resonant frequency when exposed to a radio frequency electromagnetic field of a corresponding frequency, and a capacitive element coupled to the sensor resonator member, the capacitive element comprising first and second capacitor plates configured to be deposited in a granular material such that a portion of the granular material interposed between the first and second capacitor plates forms a dielectric layer of the capacitive element, wherein the sensor is configured such that the resonant frequency is dependent on a capacitance of the capacitive element.
