1. Investigation of Fluid Behavior in Bifurcated Microfluidic Chambers Joel Ramey Advisor: Dr. David Schmidtke

2. Outline Motivation Making the apparatus Experiments Results Implications Future work http://www.ladinfo.org/wbc-rbc-large-B.jpg 8um diameter

3. Motivation What is a Leukocyte? –White blood cell Why is adhesion important? –Inflammation –Thrombosis –Atherosclerosis ~1 million deaths/year Endothelial cells Smooth muscle cells Monocytes Pool of fat David W. Schmidtkehttp://en.wikipedia.org/wiki/Ima ge:Carotid_Plaque.jpg

4. How do monocytes penetrate Ley et al…Immunology 2007

5. Why bifurcations Fox & Hugh, Heart 1966 Ku et al. Atherosclerosis. 1985

6. Research Aim Take advantage of established microfabrication techniques to study fluid dynamics with different geometries. –Easy to implement –Plethora of available geometries David W. Schmidtke

7. Photolithography Procedure Substrate Cleaning (glass slide) Layer of Photoresist (negative photoresist) UV Exposure Develop Aligning the Mask Transfer of a geometric shape from a photomask to a substrate David W. Schmidtke

8. PDMS stamps Clean pattern Pour PDMS over over pattern –Cure PDMS Peal from pattern http://faculty.washington.edu/afolch/i mages/Project_3DPDMS0.jpg

9. 1st semester Created new masks –Initially transparencies –Inherent limitations Flow experiments –Bead adhesion shows promise More new masks –Chrome

10. Apparatus Monitor VCR Video Camera Microscope Flow chamber Syringe Pump Controls shear stress Computer Bead suspension (100 x 10 3 beads/mL) Polystyrene beads. 6, 10, 20 um diameters Schmidtke

12. Investigation of flow Ran initial flow experiments with 6um beads Ran with 30º and 120º bifurcations Analyze flow Sarvepalli

18. Future 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

19. Acknowledgments Dr. Schmidtke Travis Spain Phillip Coghill Alex Dr. Johnson Dr. Keay

20. Questions?

21. Disorder of the large arteries.Atherosclerosis 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. Endothelial cells Smooth muscle cells Monocytes Pool of fat

22. In vitro Advantages –Watch experiment in real time –Process has high degree repeatability –Control over variables Disadvantages –Geometric constraints –Not an actual artery –Different surfaces

23. How do monocytes penetrate Ley et al…Immunology 2007

24. DeBakey et al. Ann. Surg. 1985 Predominant human anatomic sites for the localization of atherosclerotic lesions Ku et al. Atherosclerosis. 1985 High Shear Region (15-50dyn/cm 2 ) Low Shear Region (0-4dyn/cm 2 ) Stagnation Point Carotid artery Cross section of the carotid sinus

25. 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.

26. Research Aim 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

27. Computational simulation In vivo Models Malek et al. J.A.M.A 1999 Berger et al. Ann. Rev. Fluid Mech. 2000 Previous Studies 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 Ramos et al. Circ Res. 1999 Westrick et al. Circulation 2001 Skilbeck et al. Biorheology 2001 Malek et al. J.A.M.A 1999

28. In vivo Uses mice to study adhesion Advantages –Genetically tailored –Real results Disadvantages –Cannot watch in real time –Fluid mechanics not observed –More variability