The disclosed subject matter relates to a sensor or system for monitoring a target analyte by using a polymer solution that is capable of binding to the analyte. The sensor of the disclosed subject matter includes a viscosity-based sensor or a permittivity-based sensor. The viscosity-based sensor contains a semi-permeable membrane, a substrate, and a microchamber including a vibrational element. The permittivity-based sensor contains a semi-permeable membrane, a substrate, and a microchamber. The sensor discussed herein provides excellent reversibility and stability as highly desired for long-term analyte monitoring.