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Microcantilever Gas Chemical Sensors with Multi-modal Capability

Microcantilever Gas Chemical Sensors with Multi-modal Capability. Sarah S. Bedair 1 ( sbedair@andrew.cmu.edu ) Advisor: Gary K. Fedder 1,2 1 Department of Electrical & Computer Engineering and 2 The Robotics Institute. Motivation.

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Microcantilever Gas Chemical Sensors with Multi-modal Capability

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  1. Microcantilever Gas Chemical Sensors with Multi-modal Capability Sarah S. Bedair1 (sbedair@andrew.cmu.edu) Advisor: Gary K. Fedder1,2 1Department of Electrical & Computer Engineering and 2The Robotics Institute

  2. Motivation • Application fields: environmental monitoring, fire safety, homeland security • Need for chemical detection system • Portable, inexpensive relative to gas chromatograph systems • MicroElectroMechanical Systems (MEMS) – platform technology for chemical detection • Sensors integrated with CMOS circuitry to process and multiplex output signals • Arrays of sensors – for multi-modal detection • Enhanced selectivity • Device scaling -> improved sensitivity

  3. Sensitive layer Transducer Chemical Sensor Implementation • Implementation: • Chemically sensitive layer on a transducer gas/analyte Physico-chemical interaction Interface Circuitry Detection signal: Voltage, current, frequency, etc.

  4. Sensitive layer Transducer Chemical Sensor Modalities Sensing Mode: Example Device Type: • Sensing modes Chemresistor Resistive gas/analyte Chemocapacitor Capacitive Physico-chemical interaction Thermistor Pellistor Calorimetric Surface Acoustic Wave Cantilevers Mass

  5. Chemresistor Gas Sensor R • Sensitive layer -> resistor • Example conductive polymer - regioregular polythiophene (Rick McCullough’s group) • With analyte -> resistance change I Electrodes Sensitive layer Introduce Analyte Insulator Insulator Silicon substrate Silicon substrate

  6. Sensitive layer Transducer Chemical Sensor Modalities Sensing Mode: Example Device Types: • Sensing modes Chemresistor Resistive gas/analyte Chemocapacitor Capacitive Physico-chemical interaction Thermistor Pellistor Calorimetric Surface Acoustic Wave Cantilevers Mass

  7. Gravimetric/Mass Gas Sensors • Modeled as mass, spring, damper system • Sensitive polymer deposited on mass • Slower motion with absorbed analyte Introduce Analyte Sensitive polymer + gas Sensitive polymer

  8. Sensitive layer Transducer Chemical Sensor Modalities Sensing Mode: Example Device Types: • Sensing modes Chemresistor Resistive gas/analyte Combined these two modes in a multi-modal platform Chemocapacitor Capacitive Physico-chemical interaction Thermistor Pellistor Calorimetric Surface Acoustic Wave Cantilevers Mass

  9. Al Al SiO2 SiO2 Al Al Al Al SiO2 SiO2 Multi-modal Platform; Gravimetric & Chemiresistive Sensing Imbedded Chemresistor Sensor: Gravimetric Sensor: Bottom electrode Top metal electrode Sensitized polymer Sensing electrodes Actuator electrodes Cross section 1 μm 2 μm

  10. Conclusions • MEMS – technology for chemical detection system • Demonstration of multi-modal platform • Future work • Characterization of multi-modal approach • Exploring methods for device scaling -> improved sensitivity

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