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A MEMS RF-interrogated Biosensor (MIB) is proposed to measure the level of pH and eventually glucose concentration (Brix) in grapes. The MIB is a microfabricated biosensing structure that is comprised of a microneedle, a functionalized gel, a tuned tank oscillator circuit, and a miniature antenna. The functionalized polymer (hydrogel) changes in volume in response to changes (pH, glucose) within the grapes into which the device is inserted. This volume change induces the deflection of a capacitor plate which in turn modifies the resonance frequency of the tank circuit. This device is designed to be wireless and powerless: the changes in the tank oscillator circuit can be determined by remote RF interrogation, using a passive scheme in which the need for a local power source is made unnecessary.