1. Microsystems for selective gas sensing
28/04/2017
Microsystems for selective gas sensing
Ulrike Lehmann, MICROSENS
Alain Grisel, fév.2003

2. 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.

3. 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

4. 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

5. 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

6. 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)

7. 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

8. 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 ( kPa vs. 2.5MPa)
Lower resolution/theoretical plate
Hexane
Cyclo-Hexane
Sample: glue vapors
GC/MS measurement
MSGS system

9. 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