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M.S. Roberto Jacobe Rodrigues (Ph.D. student)

Flow and Gas Microsensors. M.S. Roberto Jacobe Rodrigues (Ph.D. student). B.S. Douglas Melman (M.S. student). Dr. Rogerio Furlan. Microsensor structure. Sensor. Gas and liquid applications. Heater. Suitable for small flow values. Sensor. Low power consumption. Fast response.

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M.S. Roberto Jacobe Rodrigues (Ph.D. student)

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  1. Flow and Gas Microsensors • M.S. Roberto Jacobe Rodrigues (Ph.D. student) • B.S. Douglas Melman (M.S. student) • Dr. Rogerio Furlan

  2. Microsensor structure Sensor • Gas and liquid applications Heater • Suitable for small flow values Sensor • Low power consumption • Fast response • Possibility of integration in microchannels

  3. Analytical model Based on: T. S. J. Lammerink et al., “Micro-Liquid Flow Sensor,” Sensors and Actuators A37-A38, 45-50, 1993 steady incompressible external laminar u

  4. Analytical modeling results for air flow • Compromise: microsensor size x sensitivity x maximum flow range

  5. 2D Simulation with Ansis/Flotran 0 to 500 sccm (tube with D = 3 mm) • Top: polysilicon ( ~ 0.6 µm) • Bottom: nitride (~ 0.2 µm) • 10 µm wide • 200 µm long • 0.7 µm above substrate 300 µm 3 mm

  6. Simulation results for air flow • Good agreement for low flow velocities • Heat dissipation by radial convection increases with flow velocity

  7. Simulation results for gas detection Filaments distance = 80 µm -DCT 300m X 300m 3 mm 40 mm • Difference in thermal diffusivity D = k/.c (m2/s) allows identification of gas contamination

  8. Fabrication

  9. Free-standing filaments • Red light emission  T ~ 1000 °C

  10. Tests

  11. Experimental results Filaments distance = 120 µm • Qualitative validation of simulations

  12. Conclusions • Feasible microstructure for flow and gas microsensors • Good qualitative agreement between analytical and numerical models and experimental results • Possibility of integration in microchannels of fluidic devices • Possibility of immediate application for identification of flow presence

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