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Repositionable Liquid Micro-Lenses With Variable Focal Length (1’st presentation). Institute : 奈微所 Name : 楊志誠 Student ID : d9635804. Outline. Introduction Theory Design and Fabrication Experimental Results Conclusion. 同質量的液體以球形的表面積最小 因此水珠通常以球形式存在 這樣才符合自由能最小化的自然法則.

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slide1

Repositionable Liquid Micro-Lenses

With Variable Focal Length

(1’st presentation)

Institute : 奈微所

Name : 楊志誠

Student ID: d9635804

slide2

Outline

  • Introduction
  • Theory
  • Design and Fabrication
  • Experimental Results
  • Conclusion

同質量的液體以球形的表面積最小

因此水珠通常以球形式存在

這樣才符合自由能最小化的自然法則

[MIT John W. M. Bush (April 2004).]

slide3

Introduction

  • Surface Tension
  • Weight scales as L3 and surface

tension scales as L1

  • Hence weight decreases more rapidly

than surface tension

  • Hence insects can walk

on water and coins can

float on water

slide4

Method of Microfludic Transfer

Micro-fludic Transfer

Centrifugal

Force

Pressure

Gradient

Capillary

毛細效應

Electric-Field

Magnetic

Electro-Osmosis

電 滲

Electro-Wetting

電 潤 濕

Dielectrophorsis

介電泳

slide5

Theory

- No moving parts -

電 潤 濕

(Electro-wetting)

介 電 泳

Dielectrophoresis (DEP)

電 滲

Electro-osmosis

slide6

Theory (Electro-Wetting) :Lippmann-Young Equation(1875)

ε 為真空中的介電係數

εr為介電材料的電介質

t 為介電材料的厚度

r 為 表面張力

低消耗功率及高速之微流體/液滴系統計與作分析

國家科學委員會補助專題研究計畫

NSC91-2218-E-007-043-

slide7

Paper Contribution :

1.None of old approaches have allowed lateral lens with high

accuracy positioning

2.Lens diameter : 700μm

Electrodes width : 100 μm

Positioning accuracy : 100μm

slide8

Design and Fabrication

Process Flow :

a) Photo-resist structure starting 525μm

thickness by HF etching

b) The grooves are filled with ITO using lift-off

c) The system covered with 800nm SiO2 layer

d) The barrier grid is etched into SiO2

e) The droplet contact is sputtered onto the wafer

using lift-off

Note:透明導電電極技術(indium tin oxide,簡稱 IT O,氧化銦錫)

slide9

Experimental Results

Movement & No movement:

1.Voltage Pulse amplitude

2.Voltage Pulse width

Condition:

Grid: 100μm mesh 300nm depth

The electrodes are covered by a dielectric layer

(800nm PECVD silicon dioxide)

slide10

Experimental Results (continue)

Lippmann´s Equation & “Lens maker’s formula”

D: diameter of the micro-lens

n: refractive index

U: Voltage

Volume : 1.9 nl

  • The turning range is in focal length

is roughly two times initial focal length

  • Increasing the voltage U therefore

increases the focal length

[2]

slide11

Conclusion

  • Precise positioning and focal tuning of liquid micro lens
  • Achieved 100 μm high-resolution positioning control with

the need for large numbers of electrodes

  • Successfully using voltage pluses (pluses width & High)

control liquid movement with the resolution of grid

spacing

slide13

Reference

[1] Modeling of Electrowetting Surface Tension for Addressable Microfludic System:

Dominant Physical Effects,Material Dependences,and Limiting Phenomena,

2003,IEEE,Bennjamin Shapriri et. al.,UCAL,USA

[2} OPTICAL CHARACTERIZATION OF REPOSITIONABLE LIQUID MICRO-LENSES,

IEEE,2007,p2573-p2576

[3] Equilibrium and dynamic behavior of micro flows under electrically induced surface tension

actuation forces Fortner, N.; Shapiro, B.;MEMS, NANO and Smart Systems, 2003. Proceedings.

International Conference on20-23 July 2003 Page(s):197 - 202 [4]. B. Shapiro, H. Moon, R. Garrell, and C. J.Kim, "Equilibrium Behavior of Sessile Drops under

Surface Tension, Applied External Fields, and Material Variations," Journal of Applied Physics

(to appear), 2002.

[5]. www-math.mit.edu/~bazant/talks/NU06.ppt

[6]. www.physics.harvard.edu/~tomhunt/present/mrs_sf_apl04.ppt

[7]. www.math.umd.edu/~dio/RIT/Biomem/Shapiro-RIT-15March07.pdf

[8] Marc Madou, Fundamentals of Microfabrication, chapter 9, CRC Press, (1997).

[9] Gregory T.A. Kovacs,Micromachined Transducers Sourcebook, chapter. 9, pp.845 McGraw-

Hill,(2000).

slide14

Appendix

Micro- & Nanofluidics

Electrical Instrumentation

Microelectronics

Micromaterial

Department of Microsystems Engineering

15 Professor

University of Freiburg,Germany

Process Technology

Systems Theorie

Simulation

Design of Microsystems

Micro-actuators

Micro-optics

http://www.imtek.de/

induced charge electro osmosis
“Induced-Charge Electro-osmosis”

= nonlinear electro-osmotic slip at a polarizable surface

Bazant & Squires, Phys, Rev. Lett. 92, 0066101 (2004).

Example: An uncharged metal cylinder in a suddenly applied DC field

Same effect for metals & dielectrics

, DC & AC fields…

www-math.mit.edu/~bazant/talks/NU06.ppt

review of dielectrophoresis dep

+

-

+

+

Review of Dielectrophoresis (DEP)

conducting cover slip

electric field lines

microfluidic chamber

suspended particle

micropost

to RF voltage source

www.physics.harvard.edu/~tomhunt/present/mrs_sf_apl04.ppt

slide18

Review of electrowetting

www.math.umd.edu/~dio/RIT/Biomem/Shapiro-RIT-15March07.pdf

slide19

氣─固─液界面的三角關係

當液體潤濕固體表面時,原本氣─固的界面被液─固的界面所取代,而氣─固與液─固之界面張力的差,稱之為「濕潤張力」。當氣─固的界面張力大於液─固的界面張力時,也就是固體和液體間的吸引力大於固體和氣體間的吸引力時,固體和氣體間的界面張力會將液─固界面拉伸。換句話說,被濕潤的固體表面有較低的界面張力,因此液體會在固體表面擴張。 當液體滴在固體表面上時,固體表面和液滴切線的夾角,就是所謂的接觸角。假使接觸角小,如水滴在玻璃基板上的情形,表示液體易濕潤固體表面。但是,如果接觸角像水銀液滴在玻璃基板上那麼大,代表液體不易濕潤此表面。而濕潤張力和接觸角的關係,可以用楊格方程式(Young's equation)表示:氣─固與液─固界面張力的差等於氣─液界面張力乘上接觸角的餘弦函數。考慮兩種極端的情形,當接觸角為 0 度時,表示液體能完全的濕潤於固體表面;當接觸角為 180 度時,代表液體完全不能濕潤於固體表面。 從固─氣的界面張力觀點來看,當接觸角越小,餘弦函數(cosθ)會越大,固─氣的界面張力也會越大,此時表示固體表面較易被濕潤。而當接觸角越大,固─氣的界面張力越低(如鐵氟龍),代表越不易被濕潤。

液滴在表面的接觸角示意圖。上圖為疏水性的接觸;下圖為親水性的接觸。

slide20

Surface tension

  • Represented by the symbol σ, γ or T, is defined as the

force along a line of unit length

  • Where the force is parallel to the surface but perpendicular

to the line.

A soap bubble balances surface tension forces against internal pneumaticpressure.

a needle floating on the surface of water.

Its weight, fw  , balanced by the surface tension forces on either side, fs  ,

Water striders using water surface tension when mating.

slide22

SURFACE TENSION

http://www.online-tensiometer.com/oberfl/frame_oberfl_values.html