The present invention provides novel tank circuits that are totally passive, and they are made of conductive-grade carbon nanotubes (CNTs) on substrates, and preferably flexible substrates. These components and structures contain no traditional electronic materials such as silicon, metal oxides, or ceramics, and they are totally organic. They may be used in applications where the resonant frequency and amplitude of the sensor can be modulated by a thermal, mechanical, or chemical signal, such as temperature, strain, pressure, vibration, or humidity. All-organic, and consequently combustible, passive RF sensors have unique applications for defense and consumer industries.