Laterally actuated amplified capacitive vapor sensor
Inventors
Mastrangelo, Carlos H. • Kim, Hanseup • LIKHITE, Rugved
Assignees
University of Utah • University of Utah Research Foundation Inc
Publication Number
US-11408846-B2
Publication Date
2022-08-09
Expiration Date
2037-10-30
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Abstract
A capacitive vapor sensor, sensor system, and method for determining a vapor concentration is provided. The capacitive sensor includes a first electrode and a second electrode. The first and second electrodes are configured to provide a bias voltage. The sensor further includes a cantilevered sensor electrode interdigitated between the first and second electrodes and having an adsorptive polymer attached to a surface of the cantilevered sensor electrode. The adsorptive polymer is configured to expand in response to adsorbing a vapor and cause a deflection of the cantilevered sensor electrode, the deflection causing a change in a differential capacitance of the first and second electrodes. A sensor indicates current at the cantilevered sensor electrode, and an electronic processor determines the change in the differential capacitance to determine a characteristic or concentration of the vapor.
Core Innovation
The invention provides a capacitive vapor sensor, sensor system, and method for determining vapor concentration. The core structure comprises a first electrode and a second electrode configured to provide a bias voltage, with a cantilevered sensor electrode interdigitated between them. An adsorptive polymer is attached to the cantilevered sensor electrode's surface. This polymer expands upon adsorbing vapor, causing the cantilevered sensor electrode to deflect. The deflection results in a change in the differential capacitance between the first and second electrodes, which is used to determine the characteristic or concentration of the vapor.
A key aspect of the design is that the deflection of the cantilevered sensor electrode can be parametrically amplified by applying a DC bias voltage to the electrodes. The bias voltage effectively softens the spring constant of the cantilevered sensor electrode, leading to an amplified response for the same amount of vapor-induced swelling of the adsorptive polymer. The system includes a sensor to detect current at the cantilevered sensor electrode, and an electronic processor calculates the change in differential capacitance based on the sensed current, which correlates to vapor concentration or presence. This structure enhances sensitivity and allows for detection even of small quantities of odorless or colorless vapors.
The method described involves steps of applying the bias voltage, detecting and amplifying the deflection caused by vapor adsorption, sensing the resulting current, determining the change in differential capacitance, and outputting the vapor characteristic. Additionally, multiple sensors can be arranged in an array, enabling either increased sensitivity and redundancy or selective detection of different vapors using various adsorptive polymers. All components can be integrated in a housing with user interface capabilities such as a display.
Claims Coverage
There are three independent claims in this patent, each introducing a distinct inventive feature centered around vapor sensing using capacitive structures.
Capacitive vapor sensor with cantilevered sensor electrode and adsorptive polymer
A capacitive vapor sensor comprising: - A first electrode and a second electrode configured to provide a bias voltage. - A cantilevered sensor electrode interdigitated between the first and second electrodes. - An adsorptive polymer attached to a surface of the cantilevered sensor electrode, configured to expand upon adsorbing a vapor and cause a deflection of the cantilevered sensor electrode. - The deflection leads to a change in differential capacitance of the first and second electrodes.
Method for determining vapor concentration using differential capacitance
A method comprising: 1. Supplying a bias voltage to a first electrode and a second electrode. 2. Deflecting a cantilevered sensor electrode in response to adsorption of a vapor by an adsorptive polymer attached to its surface, where the polymer expands with the vapor and causes the deflection. 3. The deflection causes a change in differential capacitance of the electrodes. 4. Sensing current at the cantilevered sensor electrode. 5. Determining the change in differential capacitance by an electronic processor based on the sensed current. 6. Outputting, by the processor, the vapor concentration based on the detected change in differential capacitance.
Capacitive vapor sensor system with electronic processor
A capacitive vapor sensor system comprising: - A capacitive vapor sensor with first and second electrodes configured to provide a bias voltage, a cantilevered sensor electrode interdigitated between them, and an adsorptive polymer attached to the cantilevered sensor electrode’s surface that expands and causes deflection upon adsorbing vapor, changing the differential capacitance. - A sensor coupled to the cantilevered sensor electrode to indicate current at the cantilevered sensor electrode. - An electronic processor coupled to the sensor and configured to determine the change in the differential capacitance to determine a characteristic of the vapor.
The inventive features are centered on a capacitive vapor sensing structure where vapor presence causes deflection-induced changes in capacitance, on a method utilizing this physical change to determine vapor concentration, and on a system architecture incorporating sensing and electronic processing for characterization of vapor.
Stated Advantages
The capacitive vapor sensor enables detection of vapors that are difficult to sense, including odorless or colorless vapors.
Application of a bias voltage amplifies the deflection response, increasing sensitivity and allowing detection of smaller vapor concentrations.
The system is reusable, as the adsorptive polymer can expand and contract in response to changing vapor concentrations.
Sensor arrays increase total output signal, enhancing sensitivity, noise tolerance, and redundancy.
Documented Applications
Detection of vapor concentration or presence in the atmosphere, including odorless or colorless vapors.
Sensing specific target vapors, such as water vapor, alcohols, or volatile organic compounds, by selecting appropriate adsorptive polymers.
Implementation in hand-held sensing devices with display and user interface for environmental vapor concentration readout.
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