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Development of VOCs and ozone Micro-analysers based on microfluidic devices for Aircraft Cabin Air mOnitoring (MACAO)

Periodic Reporting for period 1 - MACAO (Development of VOCs and ozone Micro-analysers based on microfluidic devices for Aircraft Cabin Air mOnitoring (MACAO))

Reporting period: 2016-02-01 to 2017-04-30

The “Development of VOC and ozone Micro-analysers based on microfluidic devices for Aircraft Cabin Air mOnitoring” (MACAO) project is focused on the development of efficient and accurate micro-analysers of various gaseous pollutants encountered in the aircraft cabin air. By measuring Volatile Organic Compounds (VOC) and ozone concentrations, whether generated inside the cabin or entering the cabin through the air conditioning systems, the project will cater for the subsequent removal of these substances and thus, in the long run, improve cabin comfort and health standards for both passengers and crew members.
The MACAO project will thus contribute to increasing the overall efficiency of more electrical aircraft, in particular by having an impact on their overall weight and power consumption through increased miniaturization compared to existing systems.
The air quality sensors developed in the project will also guarantee the long-term monitoring of cabin air quality and therefore cabin crew members and passengers will be kept safer from potentially harmful molecules.
The MACAO project aims at the investigation of possible solutions to improve air quality and cabin comfort has been defined as one of the objectives of the Clean Sky2 program. This concerns the development of devices enabling to remove air pollutants generated in the cabin or entering in the cabin through the air conditioning system. These devices will have to be associated to analysers able to monitor pollutants concentrations and thus to control the air quality in the cabin.
This project aims at developing two analytical instruments based on microfluidic devices for the measurement of major indoor air pollutants concentrations in airplanes. The first micro-analyser will measure concentrations of various VOC whereas the second one will measure the ozone concentrations.
Regarding the VOC detection, the design of a micro-column, a preconcentrator using MEMS technology has been started. The micro-heaters and temperature sensors integrated in the micro-column have already been fabricated and evaluated. The obtained results highlight the necessity to use professional masks to deposit uniform metal layers and thus appropriate resistances according to the set goals. Additionally, kinetics studies of wet etching with KOH (40%) were conducted at two different temperatures (50 and 70 °C) to help better knowledge of the wet etching technique and temperature influence on this process, which will be then used in the fabrication of three prototypes of micro-columns with different lengths.
Manufacturing of the first series of micro-columns is still in progress; five prototypes are being manufactured in LAAS platform (Toulouse) using deep reactive ion etching (DRIE) and three additional columns will be fabricated using wet etching in STnano platform (Strasbourg). Experimental tests on VOC separation efficiency of the micro-columns are expected in the next months.
The next steps will be the definition of the final geometry of the preconcentrator, its fabrication and the development of the electronic system and software for its temperature control.
Regarding the ozone detection, all efforts have been concentrated on the development of the detection cell, which is the key element. A first prototype of this colorimetric cell was made at the mechanical workshop of the ICPEES in Strasbourg. A signal acquisition software as well as an electronic card have been developed specifically. It is now possible to record the signal as a function of time.
Ambient air pollution is a reality well known all over the world and many recent studies have focused on the indoor air pollution. The effects on health are now well documented and it’s time to improve the quality of our environment. The results of this improvement will be rapidly measurable: less medicines’ and hospital costs, less children with asthma, wellness and more efficiency at work, less absenteeism, etc. Some governments are imposing rules and most countries will follow this trend sooner or later, because air quality is everybody’s business.
The products (ozone and light VOC analysers) developed in MACAO project have initially a TRL equal to 2 and 3 respectively and will be highly improved to reach at least a TRL of 5 at the end of the project. Besides, the validated sensors will also have other potential applications in diverse industrial and civil sectors, such as the automotive industry, energy plants, residential buildings, smart homes, eco-buildings, etc. Contrary to the complexity of developing more electrical aircraft systems, integration procedures in these sectors may entail fewer constraints and therefore enable the developed components to reach non-aeronautical markets quicker and more easily. Such improvement should strengthen the competitiveness of the company involved in MACAO project and in charge of the marketing, namely IN’AIR SOLUTIONS.
In this project, two reports have been delivered by IN’AIR SOLUTIONS: the first one was focused on the “Technical required specifications including integration constraints” and the second one focused on the “Specifications on validation method and qualification”. In parallel, two bibliographic reports by INSA and CNRS respectively, were written on the “Microfluidic components” and on “VOCs & ozone pollutants detection systems”. The last deliverable on the “Industrial requirement specifications” will be provided by TRONICO in its revised version by the end of august 2017.
This bibliographic reports highlight the immense potential offered by MEMS technology for obtaining miniaturized elements, in order to achieve high portability and low energy consumption of analytical instruments. Therefore, the approach implemented in this work opens up new avenues concerning future VOC microanalysers for on-site real time monitoring of indoor air quality in aircrafts.
Regarding specifically the ozone detection, although the chemiluminescence detection is more sensitive and selective as shown in the literature review, the necessary use of a gas cylinder of Nitrogen dioxide (NO2) at high concentrations (10 – 100 ppm) for its operation is not compatible with the safety constraints in aircrafts. It is why the colorimetric detection technique has been selected for ozone quantification for future developments in the framework of this project.