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LUIDICSLUIDICSNDNDLUIDICS LUIDICS urad KUCUR

Introduction

Fluid is a substance thatli d han applied shear stress

Fluidics: handling of liqug q Micro: has at least one of

S ll l■ Small volumes■ Small size■ Low energy consumption■ Use of special phenomen

continually flows under

uids and/or gasesgf the following features:

nna

MicrofluidiMicrofluidiMicrofluidics is a collective area coverMicrofluidics is a collective area coverfluids, kinetics, analysis, fabrication, cthereof.

Surface tension

ics in Natureics in Natureing a broad subjects such as microscaleing a broad subjects, such as microscaleontrol, sensing, and all the components

Stokes Flow

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Microfluidics inHemodynamics

Lotus Effect

n Nature (Cont.)

Biomechanics

Hemodynamics or hæmodynamics is the fluid dynamics of blood flow

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The Birth of M

In the period when silicon‐based MEMbegan to take off, there were no technibegan to take off, there were no techniobstacles in making simple microfluisystems. Thus, the first miniaturized gchromatography system was created aroug p y y1975. This achievement was an isolated onmost likely because the separation‐sciencommunity was not ready to develop silicy y ptechnologies for its own needs. It was oafter 1991 that the advantagesminiaturization were thrust into the spotlighp gparticularly forchromatography,

its applicationand then all sorts

microfluidic systems began to be fabricated.

Microfluidics

MSicalicaldicgasundne,nceconnlyofht,to of

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MicroTAS or LMicroTAS refers to mic

Lab on a Chipcro total analysis system.

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Growth Rate o

(Exerpted from G

of Microfluidics

Global Information, Inc.)

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Commercial/ Accademic Interest

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Analytes vs SaAnalytes v.s Saample Volumesample Volumes

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MicrofluidScale/ApScale/Ap

dics Lengthpplicationspplications

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What is a micro-fluWhat is a micro fluMicro-channelsMicro channels

■ A system manipulating fluids dimension on less than 100 m– Smallest micro-channel: N

uidic system?uidic system?Nano-tubes

in channels having cross section icro-metersNano-tube

MicroFluidics

A microfluisame width

idic channel is about theh as a human hair, 70 μm

■ Micro-Total-Analysis-Systems (TAS)

– One system to provide all ofthe possible required analyses for a given type problemAll i g t – All processing steps are performed on the chip No user interaction required– No user interaction requiredexcept for initialization

Lab on a chip■ Lab-on-a-chip

■ Micro-fluidics in nature

– Alveoli (Lung bubbles)

f

d d

■ Low sample and reagent consu■ Low sample and reagent consu■ Small physical and economic

P ll li ti d hi h th■ Parallelization and high throug■ Unique physical phenomena: u Laminar flow Capillary forces Diffusion

umption; fluid volumes (μl; nl; pl; fl)umption; fluid volumes (μl; nl; pl; fl)footprinth t i t tighput experimentation

use of effects in the micro-domain:

Microfluidics: Microfluidics: EleEle

The very interesting flow velocity profile an open channel. Such a channel (in theflow. 500nmShown in the situation for negatively chaand the cathode is at the right. In fact thwalls, since velocity drops to zero at thecomparable to the thickness of the electhttp://faculty.washington.edu/yagerp/micSelf-assembly and Nanotechnology

ectrokineticectrokinetic FlowFlow

calculated for electroösmotic pumping ine absence of backpressure) exhibits plug

arged walls; the anode is at the lefte profile is very interesting close to the

e walls over a distance that istrical double layer.crofluidicstutorial/tutorialhome.htm

Fluid MechanicsFluid MechanicsFluid MechanicsFluid Mechanics

L C ti f• Law: Conservation of mass• Law: Conservation of

momentum• Assumption:

Incompressibility• Assumption: No-slip p p

boundary• condition, i.e. velocity of thcondition, i.e. velocity of th

fluid flow at a surface is zer

ssss

s

hehe ro

BASIC PROPERBASIC PROPERTypes of fluids:

■ Newtonian fluids

■ Non-Newtonian fluids■ Non Newtonian fluids

RTIESRTIESTypes of fluid flow:

■ Laminar

■ Turbulent

NON-NEWTONIA

■ Non-linear relationship betwh ishear strain

■ Examples: paint, blood, ketcp p

AN FLUIDSU S

ween shear stress and

chup, cornstarch solutionp

Viscosity

■ Viscosity is a measure of ■ Viscosity is a measure of internal friction (resistance) to flowinternal friction (resistance) to flow

LAMINAR AND TUR

Laminar flow:

■ Fluid particles move along smo

M f l d■ Most of energy losses are due to

■ Viscous forces are the key playe

Turbulent flow:Turbulent flow:

■ An unsteady flow where fluid p

■ Inertial forces are the key playe

RBULENT FLOW

oth paths in layers

i ffo viscous effects

ers and inertial forces are negligible

particles move along irregular paths

rs and viscous forces are negligible

LAMINAR AND TU WURBULENT FLOW

REYNOLDS NUMBEREYNOLDS NUMBE

■ Measure of flow turbulenc■ Measure of flow turbulenc■ Used to help predict simila

fl id fl i ifluid flow situations.■ Re < 2000 for laminar■ Re < 2000 for laminar■ Due to small dimensions■ Re < 1 in microfluidic syst

ERER

eear flow patterns in different

tems

Couette flow:■ One of the plates moves pp p■ Steady flow between plat

N li diti li■ No-slip condition applies

parallel to the otherptess

Gi th d i■ Gives the pressure drop in an fluid in laminar flow flowing tof constant sectionof constant section.

■ Pressure-driven flow■ No-slip condition( A solid bou

velocity relative to boundary)

i ibl d t iincompressible and newtonianthrough a long cylindrical pipe

undary, the fluid will have zero applies

■ Diffusion is the transport of parconcentration to one of lower co

rticles from a region of higher oncentration by random motion.

S f t i i t■ Surface tension is a propertymolecules to like molecules)

■ When an interface is createdforces is asymmetric

■ Molecules at the surface maybulk molecules

f h i (th tt ti fy of cohesion (the attraction of

d, the distribution of cohesive

be pulled on more strongly by

W YWETTABILITY-■ wettability is determined b■ wettability is determined b

adhesive and cohesive forc■ Adhesion vs. cohesion■ Adhesion vs. cohesion■ Contact angles are a way to

interactionsinteractions

Hydrophobic

-degree of wettingby a force balance betweenby a force balance between ces.

o measure liquid-surface

Hydrophilic

Micro-scale Handling Systemg y

Small Volume MicroflTransport Devic

SubatmosphericPressure Chamber

Sample Loading And Injectionj

Electro-OsmoticuidicPumpces

Electro-PneumaticElectro-PneumaticDistributor

Fluid Fund• Definition:

A fluid is a substance thunder the application of ano matter how small the s

• Liquids and gases are very– Liquids become less viscq– Gases becomemore visc

damentals

hat deforms continuouslyshear (tangential) stress

shear stress may be.y different animalsous as T increasescous at T increases

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Fundamentals of M

• Fluid behaves as a con• Fluid ‘sticks’ to surface• Fluid sticks to surface• Fairly high Reynolds nuR i ti l f / iRe=inertial forces/viscoimplies inertia relative

acro Assumptions

ntinuumes (no‐slip condition)es (no‐slip condition)umber (Re) 

fous forcesely important

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Different AspectsDifferent AspectsFluidic interconnectsThese accomplish the coupling betbetween a microfluidic system and thelinkage is made in a simple, standardizg p ,two electronic circuits are connected.

Pumps and valvesControl elements such as valves antechnology, are complicated to fabricalab‐on‐a‐chip systems. However, thelab on a chip systems. However, theelastomers offer elegant possibilites for

Fluid injectionFluid injectionThe injection of fluids is a practical dsimple solution, especially when thamplifiable (for example proteins extramplifiable (for example, proteins extrof minute quantities of fluid remains afluid volumes.

s of Microfluidicss of Microfluidics

tween two microfluidic systems, orexterior world. It is desirable that thezed way, without leaks, similar to howy, ,

nd pumps, when made using siliconte and then difficult to integrate ontouse of ‘soft’ technologies based onuse of soft technologies based onvalves and pumps

difficulty that does not always have ae sample is very small and is notracted from a single cell) The injectionracted from a single cell). The injectionn open problem in the management of

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N flNanofluTo manipulate objects of nanometric size indeveloping ‘nanofluidics’, i.e. the field involving tdeveloping nanofluidics, i.e. the field involving tillustrate this aspect of nanofluidics, it is worthware pertinent to this field:

idi !!uidics !!n solutions, one may think of eventuallyhe study of flows in nanometer‐sized systems. Tohe study of flows in nanometer sized systems. To

wile to look at a few suggestions offered by Fujita that 

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Reasons for Fluid Be• Cube‐Square Law– quantities L3

• inertia, buoyancy, etc.– quantities L2

• drag, surface charge, etc.– quantities L

• surface tension• Non‐continuum effects– gases: Kn=λ/L, no slip, co– liquids: complex behavioassumption breaks dow

ehavioral Changes

ontinuum approximationors as continuum n

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Electro

Electrokinetic pumping and particleused to move liquids and particlesused to move liquids and particlesare implemented through surface fscales are reduced. Electrokinetic teb i il i t bl i t ibeing easily integrable into microexternal systems such as syringe pum

kinetics

e manipulation techniques are widelyat small length scales because theyat small length scales because they

forces, which scale well when lengthechniques also have the advantage offl idi t h d tofluidic systems when compared to

mps.

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ElectrooElectroo

When polar liquid, such as water, anthe surface of the solid acquires anstrongly drawn toward the surface ag yStern layer in which the ions in the lthe surface. The Stern layer thendeeper in the fluid creating a thickerdeeper in the fluid creating a thickersign, as those in the Stern layer calleTogether these two layers are called th

osmosisosmosiswall potential zeta potential

nd the solid are brought into contact,electric charge. Ions in the liquid areand form a very thin layer called they yliquid are paired with the charges oninfluences the charge distribution

r layer of excess charges of the samer layer of excess charges of the samed the diffuse or Gouy‐Chapman layer.he electric double layer (EDL).

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Zeta Pootential

http://www.tpub.com/content/doe/h1015v2/css/h1015v2_38.htm

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After assuming a Boltzmann distribut

Electric DoAfter assuming a Boltzmann distributPoisson relationship:

between the charge density E and tg yis symmetric (e.g., Na+, Cl−), the gofound to be the Poisson‐Boltzmann e

where c∞ is the concentration of ions number (valence) of each ion ε = ε εnumber (valence) of each ion, ε = εrε0Faraday’s constant. Faraday’s constantsingly‐ionized molecules—F = 9.65 × 1

tion of the charge in the EDL and the

ouble Layertion of the charge in the EDL and the

he potential , and that the electrolytep yoverning equation for the potential isequation:

far from the surface, z is the charge is the dielectric constant and F is0  is the dielectric constant, and F is

t is equal to the charge of 1 mole of104 C mol−1.

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This approximation is called the De

Electric DoublThis approximation is called the Degreatly simplifies to:

where λD  is called the Debye lengththis ordinary differential equation isbbe:

bye Hückel limit of thin EDLs and it

e Layer (Cont.)bye‐Hückel limit of thin EDLs, and it 

of the electrolyte. The solution tos quite straightforward and found to

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Electroosmmotic Flow

This potential can bedd d i t th N iadded  into  the  Navier‐Stokescalculate

equation tothe flow

produced by theelectro‐osmotic effect.

Helmholtz‐Smoluchowski eq.

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AC Electrroosmosis

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AC ElAC ElWhy does ACEO flow not cWhy does ACEO flow not celectric field switches?

l ilectroosmosischange direction as thechange direction as the 

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Electroosmootic Pumping

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Electroosmotic PPumping (Cont.)

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Electropp

+

Electrophoresis, also called cataphoresisrelative to a fluid under the influence ofrelative to a fluid under the influence of

phoresisp

Stokes’ Law

‐

s, is the motion of dispersed particles f a spatially uniform electric fieldf a spatially uniform electric field.

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ElectropElectropphoresisphoresis

Zetapotential

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Isoelectric F

Isoelectric focusing (IEF), also known as edifferent molecules by their electric celectrophoresis, usually performed on profact that overall charge on the moleculesurroundings.

ocusing (IEF)

lectrofocusing, is a technique for separatingharge differences. It is a type of zoneoteins in a gel, that takes advantage of thee of interest is a function of the pH of its

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Transverse IsoelTransverse Isoel

htt //f lt hi t d / / ihttp://faculty.washington.edu/yagerp/micro

lectric Focusinglectric Focusing

Separation of the proteins bovineserum albumin (BSA)(orange) andh l i ( ) bwheat germ lectin (green) by IEF.

fl idi t t i l/t i f/t i fht

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ofluidicstutorial/transverseief/transverseief.htm

Dielectropho

El t dElectrodes

oresis (DEP)

Dielectrophoresis (DEP)f t th ti frefers to the motion of

(oran

polarizable particlescells) suspended inelectrolyte and subjectedelectrolyte and subjectedto a nonuniform electricfield. Since the particles orcells are moving in a liquidcells are moving in a liquidelectrolyte, the DEP force isbalanced by the viscousdrag on the particledrag on the particle.

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Electric FieldElectric Field (pDEP an(pDEP an

Balance

Disttrib tionsDisttributionsnd nDEP)nd nDEP)

e of charges

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Definnitions

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