Sensor coatings for measuring environmental gases and VOCs

Sensors are essential for the control and optimal operation of processes, also in the context of Industry 4.0 and increasing digitalization.

Fraunhofer IGB functionalizes surfaces for gas and liquid sensors to detect environmental gases (NOx, SO2), volatile organic compounds (VOCs) or other molecules that are difficult to measure and are generated in production or combustion processes. For this purpose, polymers, ionic liquids or metal-organic framework structures are equipped with specific functions for binding the molecules in demand, integrated into existing sensor platforms and tested in gas measuring stands under controllable conditions.

Challenge: Limited selectivity

Commercially available gas sensors are generally used for monitoring air quality and controlling air conditioning systems or for exhaust gas measurements in automotive, medical or environmental technology. They can detect single gaseous substances like CH₄, CO, NO₂ or a wide range of volatile organic compounds like alcohols, aldehydes, ketones, etc.

A disadvantage is that they have a greater or lesser cross sensitivity to other compounds, which prevents reliable identification of the target substance. Most sensors have only limited selectivity for certain substances. The human nose has about 350 scent receptors that can be compared to gas sensors. The difference, however, is that the scent receptors of the nose respond very specifically to few gases, while gas sensors respond to many gases.

Solution: Selective sensor layers

Fraunhofer IGB develops sensor layers that are sensitive and selective for specific compounds and integrates them into the customer-specific sensor concept. For this purpose, we use established sensors, at whose sensor-active layer we modify the surface in such a way that detection becomes more specific and selective by binding the target molecule. For example, we use specific polymers, organometallic framework compounds, surface enlargements by low-pressure plasma processes, the integration of oxidic nanoparticles or ionic liquids and adapt these to the selected measurement conditions.

Advantages

By modifying the sensor-active layer, the detection of gases is much more specific and selective than before. By evaluating several sensors at the same time, where a certain analyte is most sensitively detected, more sensitive sensor arrays can be developed for certain analytes. This can be done in our gas measuring stand.

Gas measuring facility

Gas mixing plant with gas measuring stand.

Testing and optimization of sensors in gas mixing plant

We test and optimize the new sensors in our gas mixing plant with regard to their performance for the measurement of gases in a wide field. With the gas mixing plant it is possible to create a defined test atmosphere in a closed system. For this purpose, individual gases can be introduced in certain flow quantities, the air humidity can be regulated and the temperature in the pipes can be adjusted.

Measurement of

MOX
- Sulfur compounds
- NO_x
CMUT
- Ozone
- NO₂
- SO₂

Services

Development of selective coatings for sensors
Characterization of sensors at the gas measuring stand
Feasibility studies and customer-specific conceptual development
Evaluation of new processes
Surface analysis and characterization
Laboratory tests, benchmarking and validation

Applications

In the monitoring of manufacturing processes, selective and sensitive sensors can reduce costs by reducing defective products and defective batches.

In addition, a data evaluation of the recorded measurement data can be connected in real time and the right measures can then be taken.

Specific sensor surfaces for environmental gases and volatile chemical compounds
Online monitoring of industrial processes for quality assurance
Optimizable process control
Adjustable inline and online analytics