Capacitance-based humidity and gas sensing rfid tags

A radiofrequency (RF) tag system comprising:

• an antenna;
• an environmental indicator, the environmental indicator configured to be independently responsive to a plurality of environmental stimuli,
• the environmental indicator comprises:
• a first electrode operatively coupled to the integrated circuit;
• a second electrode operatively coupled to the integrated circuit;
• a dielectric material interposed between the first and second electrodes, a dielectric constant of the dielectric material having a different response to exposure to each of the plurality of environmental stimuli;
• and
• an integrated circuit operatively coupled to the antenna and the environmental indicator, the integrated circuit is configured to:
• sense a change in a capacitance of the environmental indicator;
• indicate an exposure to a first environmental stimulus of the plurality of environmental stimuli in response to the change corresponding to a first capacitance range caused by a response of the dielectric constant to the first environmental stimulus;
• and
• indicate an exposure to a second environmental stimulus of the plurality of environmental stimuli in response to the change corresponding to a second capacitance range caused by a response of the dielectric constant to the second environmental stimulus.

A method comprising:

• sensing, via an integrated circuit of a radiofrequency (RF) tag, a change in a capacitance of an environmental indicator, the environmental indicator configured to be independently responsive to a plurality of environmental stimuli, the environmental indicator having first electrode operatively coupled to the integrated circuit, a second electrode operatively coupled to the integrated circuit, and a dielectric material interposed between the first and second electrodes, a dielectric constant of the dielectric material having a different response to exposure to each of the plurality of environmental stimuli;
• outputting a first signal including a first data value, via an antenna of the RF tag, to indicate an exposure to a first environmental stimulus of the plurality of environmental stimuli in response to the change corresponding to a first capacitance range caused by a response of the dielectric constant to the first environmental stimulus;
• and
• outputting a second signal including a second data value, via the antenna, to indicate an exposure to a second environmental stimulus of the plurality of environmental stimuli in response to the change corresponding to a second capacitance range caused by a response of the dielectric constant to the second environmental stimulus.