Microfluidic devices for gas flow control

1
Microfluidic Actuators
and Sensors

• Dr. Eliphas Wagner Simoes (Post-Doc)
• Dr. Rogerio Furlan

2
Microfluidic amplifiers

• No movable part
• Flow control
• Flow mixture

3
Microchannel Technology

• Silicon wet etching - KOH - 27,4 in water

• Plasma etching - HDP plasma SF6
• based - hidraulic diameters of 40 µm

• Anodic bonding - 377C/ 800 V

4
Tests with gas (N2)
5
Flow control results
QS
QC1
QO2
QO1

• Symmetrical behavior
• Non-zero output

6
Flow gain (DQO/DQC) results

• High flow gain up to 8

7
Flow ratio results

• More uniform performance for small splitter angles

8
Analysis of internal flow with Ansys/Flotran

• Choked flow at the output of the supply nozzle

9
Analysis of internal flow with Ansys/Flotran

• Supersonic flow at the interaction region
• Possibility of shock waves formation

10
Analysis of internal flow with Ansys/Flotran

• Laminar to turbulent flow

• Continuum to slip flow

11
Main results for use with gas

• Feasibility for applications that require gas
  flow control

• Gain flow comparable to the obtained to devices
  with large dimensions

• Possibility of operation with internal
  disturbances (shock waves and turbulence) -
  application as flow mixer

• Good basis for development of microfluidic
  oscillators for flow sensor applications

12
Microfluidic oscilattor

• Flow Measurement

13
Tests with liquids

• Supply flow
• Isopropilic alcohol
• Acetone
• Distilled water
• Control flow
• Nitrogen
• Liquids

14
Supply of liquids with nitrogen control

• Possibility of control for alcohol and acetone
• Influence of viscosity, bubbles and hydrophobic
  effects for water

Increasing supply flow
15
Supply of liquids with liquid control

• Possibility of control for alcohol
• Pronounced formation of bubbles for acetone and
  water
• Flow throughout vents (Coanda Effect?)

Increasing supply flow
16
Rapid prototyping of microfluidic switches in
poly(dimethyl siloxane)and their actuation by
electro-osmotic flow J. Micromech. Microeng. 9
(1999) 211 217 - Department of Chemistry and
Chemical Biology, Harvard University
17
Main results for use with liquids

• Promising results for control with gas

• Strong influence of the type of liquid
  (viscosity)

• Possibility of hydrophobic effects - points to
  use of other materials and processes

• Can be operated with some level of suspended
  solids without clogging