Compact gas sensor with enhanced selectivity

Patent metadata

Field	Value
Publication number	US-10788470-B2
Application number	US-201615388673-A
Country	US
Kind code	B2
Filing date	Dec 22, 2016
Priority date	Dec 23, 2015
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A microelectromechanical gas sensor including a fixed part, at least one suspended part in relation to fixed part, at least one sensitive zone carried on the suspended part, the sensitive zone being able to adsorb/absorb and desorb gaseous species or families of gaseous species, a heater for heating at least the sensitive zone, a detector for detecting the adsorption/absorption and desorption of gaseous species or families of gaseous species on the sensitive zone, a controller of controlling the heater so that the heating is applied to at least the sensitive zone with one or more temperature profiles ensuring the adsorption/absorption and desorption of the gaseous species in a controlled manner so as to obtain an individual desorption of each species or families of gaseous species.

First claim

The invention claimed is:

1. A gas sensor configured for analysis of a mixture of at least two gaseous species or at least two families of gaseous species to be detected, said gas sensor comprising:
a fixed part,
at least one suspended part in relation to the fixed part,
at least one sensitive zone carried on the at least one suspended part, said at least one sensitive zone being configured to adsorb/absorb and desorb gaseous species or families of gaseous species,
a heater configured to heat the at least one sensitive zone,
a detector configured to detect the adsorption/absorption and the desorption of the gaseous species or the families of gaseous species, on the at least one sensitive zone,
a controller configured to
control the heater to heat the at least one sensitive zone to at least one first temperature to cause the adsorption/absorption of at least one of the gaseous species or the families of gaseous species,
control the detector to generate an adsorption/absorption detection signal in response to the adsorption/absorption,
control the heater to heat the at least one sensitive zone to at least one second temperature to cause the desorption of a part of the gaseous species or the families of the gaseous species,
control the detector to generate a desorption detection signal in response to the desorption, and
repeat a cycle of the steps of heating the at least one sensitive zone to at least one first temperature and heating the at least one sensitive zone to at least one second temperature, wherein

the at least one first temperature applied during a repetition of the cycle is greater than a previous at least one first temperature applied during a previous cycle,
the at least one second temperature applied during a repetition of the cycle is greater than a previous at least one second temperature applied during a previous cycle,
the repetition of the cycle is performed until all gaseous species of interest or families of gaseous species of interest are desorbed, and
the at least one sensitive zone of the at least one suspended part is in the mixture of the at least two gaseous species or the at least two families of gaseous species to be detected.

2. The gas sensor according to claim 1 , further comprising a temperature sensor for measuring a temperature of the at least one sensitive zone.

3. The gas sensor according to claim 1 , wherein the at least one suspended part is mobile and the detector comprises an actuator configured to move the at least one suspended part and a movement sensor configured to measure the movement of the at least one suspended part.

4. The gas sensor according to claim 1 , wherein the at least one suspended part is at least in part an electrical conductor and the detector measures a variation in conductivity of the at least one suspended part.

5. The gas sensor according to claim 4 , wherein the heater and the detector are integrated into the at least one suspended part.

6. The gas sensor according to claim 1 , wherein the heater is a Joule effect heater.

7. The gas sensor according to claim 6 , wherein the at least one suspended part is at least partially an electrical conductor and heats by Joule effect via circulation of a current.

8. The gas sensor according to claim 1 , further comprising a database of temperature profiles.

9. The gas sensor according to claim 1 , wherein the at least one suspended part includes several suspended parts with respective sensitive zones of different surface areas and/or having properties of adsorption/absorption and desorption different from each other.

10. The gas sensor according to claim 1 , wherein the controller is configured to control the heater to respectively heat different zones of the at least one suspended part to different temperatures simultaneously.

11. An analysis method for analysis of a gaseous mixture of at least two gaseous species or at least two families of gaseous species implementing a sensor according to claim 1 , comprising:
a) heating at least one sensitive zone in a reference state to the at least one first temperature to provoke an adsorption/absorption of gaseous species or families of gaseous species,
b) measurement of the adsorption/absorption detection signal,
c) application of the at least one second temperature to provoke the desorption of the part of the gaseous species or families of gaseous species,
d) measurement of the desorption detection signal,
e) repetition of steps a), b), c) and d) until all the gaseous species of interest or families of gaseous species of interest are separated, wherein
the at least one first temperature and the at least one second temperature applied at each cycle of repetition are respectively greater than the at least one first temperature and the at least one second temperature of a previous cycle of repetition, and
the at least one sensitive zone of the at least one suspended part is in the mixture of the at least two gaseous species or the at least two families of gaseous species to be detected.

12. The analysis method according to claim 11 , further comprising determining adsorption/absorption and desorption conditions of a next repetition in relation to the measured desorption detection signal of a current repetition.

13. The analysis method according to claim 11 , further comprising determining the at least one second temperature of step c) in relation to the measured adsorption/absorption detection signal obtained in step b).

14. The analysis method according to claim 11 , further comprising, at least prior to step a), at least one cleaning step carried out by application of a temperature provoking a desorption such that the at least one sensitive zone returns to its reference state.

15. The analysis method according to claim 11 , further comprising interrupting the analysis method when a value of the adsorption/absorption detection signal of step b) is less than a threshold value.

16. A gas detection system comprising at least one first gas sensor according to claim 1 , at least one second gas sensor including a detector and at least one sensitive zone, and a comparator and signal processing device issuing from the detector of each of said gas sensors.

17. The gas detection system according to claim 16 , wherein the at least one second gas sensor is located in a reference environment.

18. The gas detection system according to claim 16 , wherein the at least one second gas sensor is a gas sensor according to claim 1 , wherein the at least one first gas sensor and the at least one second gas sensor are located in the gaseous mixture, at least one sensitive zone of the at least one first gas sensor and at least one sensitive zone of the at least one second gas sensor being configured to adsorb/absorb and desorb different gaseous species or families of gaseous species.

19. The gas detection system according to claim 18 , wherein the at least one first gas sensor includes several first gas sensors and the at least one second gas sensor includes several second gas sensors sharing a common controller, wherein the several second gas sensors are spread in several groups arranged in a concentric manner around the several first gas sensors, the controller of the several second gas sensors controlling heaters of the several second gas sensors such that sensitive zones of each group are at a different temperature from sensitive zones of other groups.

20. The gas detection system according to claim 16 , wherein the at least one second gas sensor includes several second

Assignees

• Commissariat Energie Atomique

Inventors

• Toffoli Valeria
• Alava Thomas
• Bourlon Bertrand
• Ollier Eric

Classifications

• G01N25/4833 Primary

  specially adapted for temperature scanning · CPC title

• G01N5/04

  by removing a component, e.g. by evaporation, and weighing the remainder · CPC title

• G01N33/0059

  Avoiding interference of a gas with the gas to be measured · CPC title

• G01N33/0029

  Cleaning of the detector · CPC title

• G01N33/0016

  by regulating a physical variable, e.g. pressure or temperature · CPC title