Microsystems for selective gas sensing 20/07/2018 Microsystems for selective gas sensing Ulrike Lehmann, MICROSENS Alain Grisel, fév.2003

MICROSENS S.A. founded in 1991 as a spin-off of the CSEM (Swiss Centre for Microelectronics). Located in Neuchatel and Lausanne (Switzerland) Purpose: Applying the latest technology to manufacture industrially intelligent silicon sensors. Using microelectronic compatible processes for the miniaturization of sensing devices and sensing microsystems. Implementing application specific chemical analysis functions with the sensing element using standard or specific integrated electronic circuits.

Integrated Thermal Conductivity Gas Sensor: MTCS Gas Sensor Chip: MTCS 2200 Single Gas Sensor Devices: Mounted on TO standard packages Sensor Module: CO2/ RH% /T°C specific modes of operation RH% & T°C compensated Applications: CO2, H2, CH4, He, Ar, Vacuum

Semiconductor Gas Sensor: MSGS Gas Sensor Chip: MSGS 3000 Sensitive layer: SnO2 Single Gas Sensor Devices: Mounted on TO standard packages Sensor Module: specific modes of operation Selectivity via filters Applications: VOC, CO, CH4

MSGS Portable Gas Analysis System Increasing importance of monitoring air quality Indoor air, outdoor air, breath Measuring Volatile Organic Compounds (VOC) Challenge: Multitude of components SnO2 gas sensors for detection of VOCs Gas sample pre-treatment to increase sensor selectivity Gas chromatography as standard application for characterizing mixed gas samples Separation of sample compounds by their travelling time through a capillary Easy to use and portable gas analysis system

MSGS Portable Gas Analysis System Detection of VOC (Volatile Organic Compounds) via a portable simplified gas chromatography system Microfabricated capillary for the separation of the gaseous compounds Micro-gas sensor (MSGS3000) for the detection of the gaseous compounds Low pressure (< 0.5 bar) Low/medium temperature ( < 60°C) Short measurement time (< 5 min) Low power consumption (battery powered) Detector Carrier gas Column Sample Microfabricated column (2.5cm x 2.5cm) SnO2 gas microsensor (MSGS 3000i)

MSGS Portable Gas Analysis System Sensing module Capillary fabricated in Si with glass cover Pt heater element for temperature stabilization (40 – 60°C) Stationary phase: PDMS (Polydimethylsiloxane) Fixed mounting of the capillary to the sensor electronics Alignment of sensing area and capillary outlet 10mm Alignment of sensor and capillary 10mm Heated capillary

MSGS Portable Gas Analysis System Separation of VOC (solvents: acetone, hexane, cyclohexane) Comparison with standard gas chromatography (GC/MS) Shorter measurement time (130s vs. 20min) Lower pressure (15 - 45kPa vs. 2.5MPa) Lower resolution/theoretical plate Hexane Cyclo-Hexane Sample: glue vapors GC/MS measurement MSGS system

MSGS Portable Gas Analysis System Simplified gas chromatography – adapted for the detection of chosen compounds MSGS gas sensor of high sensitivity but low selectivity Microfabricated column for separating gaseous components before arrival at gas sensor to increase selectivity Low pressure = can be driven by miniature pumps Automated use via electronic control Electronic valves Microcontroller and USB interface Short analysis time (130s) Battery powered (9V, ideally) Easy-to-use 5 cm