•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

Sensor

Analytical modelAnalytical model

22

2,1 .4..2

1

R

Duu

D

Based on: T. S. J. Lammerink et al., “Micro-Liquid Flow Sensor,” Sensors and Actuators A37-A38, 45-50, 1993

externalsteady

laminarincompressible

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 byradial convection

velocity

Simulation results for gas detection

Filaments distance = 80 µm

•Difference in thermal diffusivity D = k/.c (m2/s)

40 mm

3 mm

-DCT300m X 300m

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

ConclusionsConclusions

•Feasible microstructure for flow and gas Feasible microstructure for flow and gas microsensorsmicrosensors

•Good qualitative agreement between Good qualitative agreement between analytical and numerical models and analytical and numerical models and experimental resultsexperimental results

•Possibility of integration in Possibility of integration in microchannels of fluidic devicesmicrochannels of fluidic devices

•Possibility of immediate application for Possibility of immediate application for identification of flow presenceidentification of flow presence