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Gas Flows in Micro Electro Mechanical Systems

Periodic Report Summary - GASMEMS (Gas flows in micro electro mechanical systems)

GASMEMS is a European training network for young researchers in the field of rarefied gas flows in micro-electromechanical systems.

GASMEMS is a Marie Curie Initial Training Network (ITN) supported by the European Commission in the framework of the People Programme of the Seventh Framework Programme (FP7).
- Network coordination: Institut National des Sciences Appliquées de Toulouse (INSA), University of Toulouse, France
- Network coordinator: Prof. Stéphane COLIN (stephane.colin@insa-toulouse.fr)
- Network assistant coordinator: Dr Lucien BALDAS (lucien.baldas@insa-toulouse.fr)
- Administrative coordinator: Chloé PRADO (chloe.prado@insa-toulouse.fr)
- Website: http://www.gasmems.eu

Project objectives and recruitments:

Gas flows in microsystems are of great interest for various applications that touch almost every industrial field: fluidic microactuators for active control of aerodynamic flows, vacuum generators for extracting biological samples, mass flow and temperature micro-sensors, pressure gauges, micro heat-exchangers for the cooling of electronic components or for chemical applications, micropumps and microsystems for mixing or separation for local gas analysis, mass spectrometers, vacuum and dosing valves.

The main characteristics of gas microflows is their rarefaction, the level of which often requires a modelling both by continuous and molecular approaches. The role played by the interaction between the gas and the wall becomes essential and it is generally badly known. Numerous models of boundary conditions are currently in confrontation and require an empirical adjustment strongly dependent on the micro manufacturing techniques. On the other hand, the experimental data are fragmentary and difficult to confront. Most of them do not address heat transfer and gas mixtures issues.

The GASMEMS network has been built from several existing collaborations within bilateral programmes and national networks, involving European research teams specialised in gaseous microfluidics. However, there was no global coordination of the research efforts in the field of gas microflows at the European level.

Thus, the two primary objectives of this ITN project are:
- to structure research in Europe in the field of micro gas flows to improve global fundamental knowledge and enable technological applications to an industrial and commercial level;
- to train early stage researchers (ESRs) and experienced researchers (ERs) at a pan-European level, with the aim to providing them both a global overview on problems linked to gas flow and heat transfer in microsystems, and advanced skills in specific domains of this research field.

15 early stage researchers (ESRs), 4 experienced researchers (ERs) and 2 visiting scientists (VSs) have been recruited during this reporting period in three complementary fields, with the following scientific objectives which correspond to work packages (WPs) 1 to 3:

- WP1: Dynamics of gas microflows (5 ESRs, 2 ERs and 1 VS recruited)
1-a) improvement of the existing analytical and numerical models;
1-b) theoretical and experimental analysis of the behaviour of mixture of gas microflows;
1-c) development of new experimental techniques to measure velocity inside microdevices.

- WP2: Heat transfer in gas microflows (6 ESRs and 1 ER recruited - 1 VS to be recruited in the next reporting period)
2-a) improvement and validation of heat transfer models for gas microflows;
2-b) improvement of the experimental data base on the convective heat transfer for gas microflows;
2-c) development of new experimental techniques to measure the gas temperature.

- WP3: Gas-materials interactions (4 ESRs, 1 ER and 1 VS recruited - 1 ER to be recruited in the next reporting period)
3-a) determination of accommodation coefficients;
3-b) analysis of the links between the fabrication processes of microdevices and the thermal and dynamic behaviour of gases;
3-c) experimental analysis and modelling of microflows with reactive gases.

Work performed since the beginning of the project:

The first two events of GASMEMS have been successfully organised in Eindhoven (First workshop and summer school, 7-11 September 2009) and in Les Embiez (Second workshop and summer school, 5-10 July 2010). They welcomed an average number of 50 participants who expressed a high level of satisfaction.

A website has been designed and widely used for scientific exchanges within the network and for communication of the network activities out of the network. Four executive board meetings and two supervisory board meetings have been organised.

In spite of a general delay in the recruitment from the foreseen schedule, the overall progress of the project is very satisfactory and generally in line with the initial plan. The overall progress of the project has been monitored by task coordinators (Task are related to scientific fields: dynamics of gas microflows, heat transfer in gas microflows, gas-materials interactions) and by group coordinators (Group are related to scientific tools: modelling and simulation, experiments and measurements, materials and manufacturing). This cross supervision of the ESRs and ERs works has allowed increased interaction between complementary individual projects, both from a scientific and training point of view.

First significant scientific results have been obtained in modelling and simulation of gas microflows, involving all basic methodologies: extended hydrodynamics, DSMC, kinetic modelling and molecular dynamics. Interesting new results concern the development of effective mean free path models to extend the NS equations applicability, the simulation of transient flows to model unsteady configurations, investigations of separation phenomena due to diffusion in gas mixtures, the implementation of repulsive-attractive intermolecular potentials, coupling between MD / DSMC / CFD codes and implementation of high order slip and jump boundary conditions.

Development of new experimental techniques is in progress: a test facility of micro molecular tagging velocimetry for gas microflows has been designed and will be assembled soon, outline concepts have been developed for micro particle image velocimetry adapted to gas microflows and a micro interferometry platform has been developed for mixing studies. Experimental databases are being completed with data on highly rarefied flows and on flow of gas binary mixtures in microsystems. Testing on a micro-heat exchanger has been commenced, a review of micro-sensors for temperature has been completed and a thermal creep test facility has been designed.

Specific fabrication techniques have been implemented and new microdevices and sensor arrays have been manufactured for supporting the experimental work, which plays a key role in the analysis of the developed theoretical models and numerical simulations in progress.

These scientific results have been already published in 10 international journal papers with high impact factor, and in more than 50 proceedings papers of international conferences. 10 other communications have been made in scientific conferences and about 50 lectures have been given by GASMEMS members in the summer schools organised by the network.

Expected final results

The objectives of the initial plan are globally achievable. They should be concluded by an increased number of publications, a final conference and a handbook dedicated to researchers and engineers working in the field of gas microflows.