Patent ID: 8786432

Claim:
An apparatus comprising: a cantilevered element including a coating material having an affinity for a compound; a first capacitive plate spaced from and capacitively coupled to the cantilevered element, wherein the first capacitive plate is configured to induce a vibration in the cantilevered element at a frequency related to a mass of the cantilevered element; a second capacitive plate spaced from and capacitively coupled to the cantilevered element; and a frequency detector coupled to the second capacitive plate, the frequency detector adapted to detect a change in vibrational frequency of the cantilevered element as a result of particles of the compound coupling to the coating material, wherein the frequency detector is configured to generate an output associated with the vibrational frequency of the cantilevered element, and wherein the output is configured to be used by a processor to generate an alert when a threshold associated with the vibrational frequency is satisfied.