2009/1/6

Sensing and Actuation in Miniaturized systems

Final report

Hello everyone !!!!!

I am Wu Chih-Wei !!!!!

2009/1/6

2009/1/6

Outline

Introduction

Fabrication

System setup

Results and discussion

Conclusion

2009/1/6

Outline

Introduction

Fabrication

System setup

Result and discussion

Conclusion

2009/1/6

ACTUATED BY EWOD

PIV INVESTIGATION OF 3-DIMENSIONAL FLOW IN DROPS

Introduction

The change in contact angle due to an applied potential difference between solid and liquid

EWOD = Electrowetting-On-Dielectric

2009/1/6

PIV INVESTIGATION OF 3-DIMENSIONAL FLOW IN DROPS

Introduction

PIV = Particle Image Velocimetry

Flow direction

mirrorLaser

x

y

t t’

Image plane

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Introduction

PIV measurement in micro-channel flow!

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Outline

Introduction

Fabrication

System setup

Result and discussion

Conclusion

2009/1/6

Fabrication

cytop fluoropolymer

SiO2

ITO

Glass wafer

droplet

Secure seal

FEATURES： Leak-proof chambers are temperature resistant and eliminate evaporation

2009/1/6

Outline

Introduction

Fabrication

System setup

Result and discussion

Conclusion

2009/1/6

System setup

μPIV system

EWOD droplet actuation system

2009/1/6

System setup

2D velocity field near the mid-height of the drop

2009/1/6

Outline

Introduction

Fabrication

System setup

Result and discussion

Conclusion

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Result and discussion

50um100um150um200um250um300um350um

Entire stack of 2D velocity fields

computing

Continuity equation

(Local form of conservation equation)

Side view of the Droplet

Image plane 3D VELOCITY FIELDS!!!!

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Result and discussion

A strong downward flow due to the eletro-wetting from the bottom substrate is observed near the nose of the droplet

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Result and discussion

To understand net effect of the forward-back motions on mixing within the droplet

Measure the overall displacement of the first image from all PIV image pairs

Forward-back motion is inefficient for droplet mixing!!(reverse motion return the particles near their initial position)

2009/1/6

Outline

Introduction

Fabrication

System setup

Result and discussion

Conclusion

2009/1/6

Conclusion

1、 Our experimental finding shows the flow in a 3D droplet indeed deviates significantly from the parabolic flow profile used in current flow simulations

2、 It would be desirable to develop a reduced dimension model that is computationally tractable while preserving the essential information about the 3D velocity

3、 Due to the reversibility of the flow, a simple forward-back motion is inefficient for mixing , effective mixing has to be accomplished through irreversible movements.

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THANK YOU FOR YOUR ATTENTION!!!!

2009/1/6

Bonus Information!

Max Velocity： 120 um/s

UpMiddledown

100µm100µm

Channel wall

Channel wall

100 µm

Experimental Data by Y.L.Lin 2007