Microbar sensor
First Claim
1. An apparatus for detecting the presence of a predetermined vapor phase chemical in a monitored atmosphere comprising:
- a piezoelectric transducer having a least one cantilevered spring element secured thereto, said spring element having an area thereof coated with a chemical having an affinity for said predetermined vapor phase chemical;
oscillator means for stimulating said transducer at or about a resonant vibrational frequency of said cantilevered spring element; and
,vibration detection means comprising photo-detection means for emitting a signal in synchronization with said spring element vibration for measuring a vibrational frequency change in said spring element due to a change in the vibrated mass of said spring element.
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Accused Products
Abstract
A mass microsensor is fabricated with a microcantilever oscillated by a piezoelectric transducer. A chemical coating having absorptive or adsorptive affinity for a specifically targeted chemical or compound is applied to the microcantilever for oscillation in the monitored atmosphere. Molecules of the targeted chemical attach to the microcantilever coating resulting in an oscillating mass increase which influences the resonant frequency of the microcantilever oscillation. The rate at which the coated microcantilever accumulates the target chemical is functional of the target chemical concentration. Consequently, the extent of microcantilever oscillation frequency change is related to the concentration of the target chemical within the monitored atmosphere. Such oscillation frequency changes are detected by a center-crossing photodiode which responds to a laser diode beam reflected from the microcantilever surface resulting in an output frequency from the photodiode that is synchronous with the microcantilever frequency.
210 Citations
20 Claims
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1. An apparatus for detecting the presence of a predetermined vapor phase chemical in a monitored atmosphere comprising:
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a piezoelectric transducer having a least one cantilevered spring element secured thereto, said spring element having an area thereof coated with a chemical having an affinity for said predetermined vapor phase chemical; oscillator means for stimulating said transducer at or about a resonant vibrational frequency of said cantilevered spring element; and
,vibration detection means comprising photo-detection means for emitting a signal in synchronization with said spring element vibration for measuring a vibrational frequency change in said spring element due to a change in the vibrated mass of said spring element. - View Dependent Claims (2, 3, 4)
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5. An apparatus for detecting the presence of a predetermined vapor phase chemical in a monitored atmosphere comprising:
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a piezoelectric transducer having at least one cantilevered spring element secured thereto, said spring element having an area portion along substantially the entire length thereof coated with a chemical having an affinity for said predetermined vapor phase chemical; oscillator means for stimulating said transducer at or about the resonant vibrational frequency of said cantilevered spring element; and
,vibration detection means for measuring a vibrational frequency change in said spring element due to a change in the vibrated mass of said spring element.
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6. A method for detecting the presence of a predetermined vapor phase chemical in a monitored atmosphere comprising the steps of:
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fabricating a cantilever spring element having a structural base secured to a piezoelectric transducer; coating a surface portion of said spring element along substantially the entire length thereof with a chemical having an affinity for said predetermined vapor phase chemical; electrically driving said transducer at or near a resonance frequency of said spring element. exposing said coated and driven cantilever spring element to a monitored atmosphere, measuring a vibrational frequency change of said cantilever spring element over a predetermined time period in said monitored atmosphere; and relating said vibrational frequency change to a concentration value of said predetermined vapor phase chemical in said monitored atmosphere. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for detecting the presence of a predetermined vapor phase chemical in a monitored atmosphere comprising:
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a piezoelectric transducer having a plurality of cantilevered spring elements secured thereto, each of said spring elements having substantially the same resonant vibrational frequency and a respective area thereof coated with a chemical having an affinity for a predetermined vapor phase chemical; oscillator means for stimulating said transducer at or about the resonant vibrational frequency of said cantilevered spring elements vibration detection means for measuring a vibrational frequency change respective to each of said plurality of spring elements due to a change in the vibrated mass respective to each spring element. - View Dependent Claims (18, 19, 20)
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Specification