Investigation of fluid behavior in bifurcated microfluidic chambers
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Investigation of Fluid Behavior in Bifurcated Microfluidic Chambers. Joel Ramey Advisor: Dr. David Schmidtke. Outline. Motivation Making the apparatus Experiments Results Implications Future work. 8um diameter. http://www.ladinfo.org/wbc-rbc-large-B.jpg. Motivation. Monocytes.

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Investigation of fluid behavior in bifurcated microfluidic chambers

Investigation of Fluid Behavior in Bifurcated Microfluidic Chambers

Joel Ramey

Advisor: Dr. David Schmidtke


Outline
Outline Chambers

  • Motivation

  • Making the apparatus

  • Experiments

  • Results

  • Implications

  • Future work

8um diameter

http://www.ladinfo.org/wbc-rbc-large-B.jpg


Motivation
Motivation Chambers

Monocytes

Endothelial cells

Pool of fat

Smooth muscle cells

  • What is a Leukocyte?

    • White blood cell

  • Why is adhesion important?

    • Inflammation

    • Thrombosis

    • Atherosclerosis

      • ~1 million deaths/year

David W. Schmidtke

http://en.wikipedia.org/wiki/Image:Carotid_Plaque.jpg


How do monocytes penetrate
How do monocytes penetrate Chambers

Ley et al…Immunology 2007


Why bifurcations
Why bifurcations Chambers

Fox & Hugh, Heart 1966

Ku et al. Atherosclerosis. 1985


Research aim
Research Aim Chambers

  • Take advantage of established microfabrication techniques to study fluid dynamics with different geometries.

    • Easy to implement

    • Plethora of available geometries

David W. Schmidtke


Photolithography Procedure Chambers

Transfer of a geometric shape from a photomask to a substrate

  • Substrate Cleaning (glass slide)

  • Layer of Photoresist

  • (negative photoresist)

  • Aligning the Mask

  • UV Exposure

  • Develop

David W. Schmidtke


Pdms stamps
PDMS stamps Chambers

  • Clean pattern

  • Pour PDMS over

    over pattern

    • Cure PDMS

  • Peal from pattern

http://faculty.washington.edu/afolch/images/Project_3DPDMS0.jpg


1st semester
1st semester Chambers

  • Created new masks

    • Initially transparencies

    • Inherent limitations

  • Flow experiments

    • Bead adhesion shows

      promise

  • More new masks

    • Chrome


Apparatus
Apparatus Chambers

Bead suspension (100 x 103 beads/mL)

Polystyrene beads. 6, 10, 20 um diameters

Flow

chamber

Syringe

Pump

Controls shear stress

Video

Camera

Microscope

VCR

Monitor

Computer

Schmidtke


Investigation of flow
Investigation of flow Chambers

  • Ran initial flow experiments with 6um beads

  • Ran with 30º and 120º bifurcations

  • Analyze flow

Sarvepalli


Future
Future Chambers

  • Look more closely at fluid dynamics in main branch

  • Run computational fluid dynamics for actual pattern

  • Analyze flow with beads at apex

  • Run experiments with leukocytes

  • Look into using pulsatile flow


Acknowledgments
Acknowledgments Chambers

  • Dr. Schmidtke

  • Travis Spain

  • Phillip Coghill

  • Alex

  • Dr. Johnson

  • Dr. Keay


Questions
Questions? Chambers


Atherosclerosis Chambers

Monocytes

Endothelial cells

Pool of fat

Smooth muscle cells

Disorder of the large arteries.

Atheroma formation: accumulation of fatty substances, cholesterol and cellular waste products.

  • Major cause of morbidity in the United States:

  • Affects close to 60 million Americans

  • Contributes to 33% of all deaths in U.S each year.


In vitro
In vitro Chambers

  • Advantages

    • Watch experiment in real time

    • Process has high degree repeatability

    • Control over variables

  • Disadvantages

    • Geometric constraints

    • Not an actual artery

    • Different surfaces


How do monocytes penetrate1
How do monocytes penetrate Chambers

Ley et al…Immunology 2007


Predominant human anatomic sites for the localization of atherosclerotic lesions

High Shear Region (15-50dyn/cm2)

Low Shear Region (0-4dyn/cm2)

Cross section of the carotid sinus

Carotid artery

Stagnation Point

DeBakey et al. Ann. Surg. 1985

Ku et al. Atherosclerosis. 1985


Schematic sudden expansion flow chamber. H, chamber height downstream of expansion; h chamber height upstream of expansion; S, gasket thickness; x coordinate parallel to glass slide; y, coordinate normal to glass slide.


Research Aim downstream of expansion; h chamber height upstream of expansion; S, gasket thickness; x coordinate parallel to glass slide; y, coordinate normal to glass slide.

Take advantage of the microfabrication technologies to study the pattern of cell adhesion and rolling at bifurcated geometries

  • Techniques easy to implement

  • Many different geometries are available


Malek et al. downstream of expansion; h chamber height upstream of expansion; S, gasket thickness; x coordinate parallel to glass slide; y, coordinate normal to glass slide.J.A.M.A 1999

Skilbeck et al. Biorheology 2001

Previous Studies

  • In vivo Models

Ramos et al. Circ Res. 1999

Westrick et al. Circulation 2001

  • Computational simulation

Malek et al. J.A.M.A 1999

Berger et al. Ann. Rev. Fluid Mech. 2000

  • Glass models of bifurcations

Karino et al. J. Biomechanics 1990

Pedersen et al. Biomechanics 1992

Malinauskas et al. Atherosclerosis 1998

  • Sudden Expansion Flow Chambers

Barber et al. Am. J. Physiology 1998

Skilbeck et al. Biorheology 2001

Skilbeck et al. Arterioscler Thromb Vasc Biol. 2001


In vivo
In vivo downstream of expansion; h chamber height upstream of expansion; S, gasket thickness; x coordinate parallel to glass slide; y, coordinate normal to glass slide.

  • Uses mice to study adhesion

  • Advantages

    • Genetically tailored

    • Real results

  • Disadvantages

    • Cannot watch in real

      time

    • Fluid mechanics not

      observed

    • More variability


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