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

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

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

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

2D Simulation with Ansis/Flotran 3 mm 300 µm 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

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

Simulation results for gas detection Filaments distance = 80 µm Difference in thermal diffusivity D = k/ .c (m 2 /s) 40 mm 3 mm  -DCT 300  m X 300  m allows identification of gas contamination

Fabrication

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

Tests

Experimental results Filaments distance = 120 µm Qualitative validation of simulations

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