Micro-sensors based on thermal transduction for steady and unsteady flow measurements Abdelkrim Talbi 7/11/2013 Institute of Electronic Microelectronic and Nanotechnologies (IEMN) A.Talbi, J-C. Gerbedoen, R. Viard, L. Gimeno, V. Preobrazhensky, A. Merlen and P. Pernod 1- LIA LICS/LEMAC - IEMN - UMR CNRS 8520, ECLille, PRES Université Lille Nord de France, France 2- Onera, chemin de la hunière 91123 Palaiseau 3- Thurmelec 1
Outline Introduction Context and motivation : MEMS for active flow control (actuators and sensors) Thermal Flow Sensors (TFS): Design and principle Thermal structures: Design constraints Thermal structures: Fabrication & Characterization Thermal Flow Sensors: Characterization under flowing flow In plane Thermal Structure : Hot wire Out of plane Thermal Structure : Hot wire In plane Thermal Structure : Pressure sensor (Pirani effect) Conclusions & Perspectives 2 2
Introduction Context 1.3 Active flow control using MEMS Boundary layer separation, drag reduction, engine noise control, etc Configurations: S ducts, airplane wings and Ahmed car models Micro-Magneto-Electro-Mechanical Systems (MMEMS) based Micro-valves for active flow control Elaboration /Design Actuation strategy Fabrication Metrological setup Performance tests/ reliability Network realization, connexion to the macroscopic world Wind tunnel tests 3
Introduction Context 2.3 Pulsed Power ~ 300mW Pin=0.2Bars Vmax=120m/s Rate of modulation channel modulation Normally off Frequency (Hz) Synthetic 8 mm x 8 mm 600 µm Power ~ 500mW Frequency=600Hz V max = 55 m/s 4
Introduction Motivation 3.3 - Closed-loop flow control - Monitoring the flow delivered by micro-valves - Understanding behavior of complex flow (turbulent flow) Measurement tools with high spatial and temporal resolution Development of Sensors Enabling : - Simultaneous measurements of different unsteady physical quantities at a point, - Measurement of local and instantaneous velocity gradients or vorticity. - Integration in a complex surface - Very small - Highly sensitive and ultra low resolution - High dynamic range - Large frequency bandwidth - Low cost surface compatible micro-machining process - Integration in a complexe surface 5
Outline Introduction Thermal Flow Sensors (TFS): Design and principle Thermal structures: Design constraints Thermal structures: Fabrication & Characterization Thermal Flow Sensors: Characterization under flowing flow Conclusions & Perspectives 6 2
Thermal Flow Sensors (TFS): Design and principle Thermal structure : Design and constraints 1.6 The proposed designs In plane hot wire Out of plane hot wire 7
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Operating principle 2.6 wire SiO2 micro beam width 2 um 10 um thickness 60 nm 200 nm length 60 um 40 um Geometrical parameters of the sensor Comsol simulations of thermal response versus an electrical heating signal at zero flow Time response Frequency cut off ~ 5kHz time response ~ 200µs 8
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Operating principle environment Conduction 2.6 convection heat transfer Radiation heater element conduction heat transfer through support thermal insulation structure conduction heat transfer through air gap substrate Geometrical parameters optimization Multi-parameters measurement (T, P, Velocity) 9
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Operating principle environment Conduction 2.6 convection heat transfer Radiation Temperature measurement heater element conduction heat transfer through support thermal insulation structure conduction heat transfer through air gap substrate Geometrical parameters optimization Multi-parameters measurement (T, P, Velocity) 9
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Operating principle environment Conduction Radiation 2.6 convection heat transfer Velocity measurement (shear stress) Temperature measurement heater element conduction heat transfer through support thermal insulation structure conduction heat transfer through air gap substrate Geometrical parameters optimization Multi-parameters measurement (T, P, Velocity) 9
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Operating principle environment Conduction Radiation 2.6 convection heat transfer Velocity measurement (shear stress) Temperature measurement heater element conduction heat transfer through support thermal insulation structure Pressure measurement conduction heat transfer through air gap substrate Geometrical parameters optimization Multi-parameters measurement (T, P, Velocity) 9
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Fabrication process 3.6 Schematic of the fabrication procedure SEM images of the fabricated structure 1. SiO2 (PECVD) deposition for thermal isolation 5. Lift-off process 2. photoresist undercutting and Pt deposition by evaporation 6.Definition of SiO2 pattern 3. Lift-off process 7. SiO2 etching in CF4/CHF3 mixture RIE plasma 4. photoresist undercutting and Au deposition by sputtering 8. Isotropic etching of Silicon using XeF2 in vapor phase Silicon Gold Resist SiO2 Pt 10
Thermal Flow Sensors (TFS): Design and principle In plane thermal structure: Electrical and Thermal characterizations 4.6 IR thermography image of the fabricated structure - Effective power in the heater ~ 6 mw - Focus x12 (2um/pixel) High performance of the thermal insulation: Temperature elevation 12.5 C. Sensitivity ~3000ppm/ C 11
Thermal Flow Sensors (TFS): Design and principle Out of plane thermal structure 5.6 Schematic of the fabrication procedure SEM image of the fabricated structure Nano-crystalline diamond 2um: (Pt/(Ni/W)n/Pt 12
Thermal Flow Sensors (TFS): Design and principle Out of plane thermal structure 6.6 Electrical and thermal characterizations low driving power IR thermography image of the fabricated structure ( Power bias= 6mW) : Focus x12 (2um/pixel) good thermal insulation 13
Outline Introduction Thermal Flow Sensors (TFS): Design and principle Thermal Flow Sensors: Characterization under flowing flow In plane Thermal Structure : Hot wire Out of plane Thermal Structure : Hot wire In plane Thermal Structure : Pressure sensor (Pirani effect) Conclusions & Perspectives 14 2
1.3 voltage for the integrated sensor located near the inlet (sensor 1). The bias voltage was fixed to 10V. This measurement is compared with the outlet velocity delivered by a calibrated commercial Dantec oot characteristic according to the King s law. More detailed investigation of this hot wire anemometer (CT constant temperature operating mode) located outside the outlet. Such a d heating power. The relative output voltage versus flow rate exhibit the typical II.3 - Caractérisation des microvalves individuelles livrées comparison can be an easy way to calibrate dynamically integrated sensors since generally flow stic for laminar and turbulent flow. The sensitivity decreases with increasing the Figure 6: Vues de détails sur le packaging individuel des valves meters only work in quasi-static conditions. We clearly observe that the signal of the integrated Fig. 11 for 5mW and 20mW bridge bias powers. The sensor shows different sensor reproduced quick velocity variations related to the actuation process while these features ogen flow. The dependence of the relative voltage bridge output on the gas flow were damped outside the system. Nevertheless, the overall features are the same exhibiting the w controllers (VOGTLIN Instruments: 117102-482477-Air-14). The tests were Figure 12-a: Photograph of the Assembled micro-valve: The sensor is positioned on the ts were performed by connecting the sample to a reference gas line, equipped front-side of the silicon micro-channel. The micro-valve has overall dimension of 1! 2! ure 10: Thermal flow sensor integrated in a packaging with ro-channel 1 cm3. In plane Thermal Structure : Hot wire same high signal to noise ratio. Thermal Flow Sensors: Characterization under flowing flow Les microvalves ont été caractérisées au LEMAC/IEMN sur un banc test dédié utilisant un fil chaud un dispositif contrôlé de mise sous pression, et le dispositif de commande des microvalves (figure 7) Les tests ont été réalisés avant livraison et en retour d essais. und in [27, 29]. Sensitivity of 70mV/(L.min-1)0.33 for voltage bias of 10V (~20 mw) ure 11: Sensor relative output voltage versus mass flow rate at erent heating power (Voffset =1.35V for bridge bias power=5mw, set=2.7 for bridge bias power=20mw). Figure 7: Banc de test LEMAC/IEMN des micro-valves 15
In plane thermal sensor for Flow Rate measurements Out of plane Thermal Structure : Hot wire 2.3 16
In plane thermal sensor for pressure measurements In plane Thermal Structure : Pressure sensor (Pirani effect) 3.3 Technological process of surface suspended Platinum hot wire Air thermal conductivity versus pressure for suspended wire with a gap of 300nm. 1- localized Aluminum deposition+ W or Ge thin sacrificial film deposition 4- Deposition of Au for electrical contact 2- SiO2 PECVD deposition 5- SiO2 etch 2- Localized Pt deposition 6- Isotropic etching of W using XeF2 Silicon Gold Resist SiO2 Pt 17 SEM image of the fabricated structure
In plane thermal sensor for pressure measurements In plane Thermal Structure : Pressure sensor (Pirani effect) 3.3 SEM image showing the nanogap IR thermography image of the fabricated structure ( Vbias of 4V : Pheater: 10 mw) : Temperature variation of 12 C 18
Conclusions and perspectives The design and fabrication of fast, robust and highly sensitive integrated thermal flow sensors (in plane and out of plane) are successfully achieved In-plane hot wire High robustness High sensitivity 70mV/(L.min -1 ) 0.33 Wide dynamic range of measurement ((0-10L/min) Fast response time (200us in CC mode). Enable an integration on solid or flexible surface, and inside micro-channel Enable an use as a multi-parameters sensor combining distributed resistors around the heater element: the case of pressure measurement is demonstrated Out of plane hot wire - New design of micro scale hot-wire probe with characteristics similar or better to those of conventional hot-wire probes and presenting better spatial resolution and offering the scaling down possibility without reducing performance. This technology offers a concrete solution for practical and fundamental fluid mechanics particularly for closed loop aerodynamic control, micro-fluidics devices monitoring, measurement of turbulent flow. 19
Conclusions and perspectives Perspectives Evaluation of effective performances for shear stress and pressure measurements (resolution, distribution over a surface, fluctuations). Evaluation of the possibility of use in closed loop reactive flow control Development of new concept enabling : - Simultaneous measurements of different unsteady physical quantities at a point, - Measurement of local and instantaneous velocity gradients or vorticity. - Integration in a complex surface Further progress in design will need a strong coordination between : simulations, experiments and theoretical approaches 20
Thanks for your attention 21