1. The Impact of Surface Heterogeneity on Particle Deposition Melissa Sy Department of Chemical Engineering California State Polytechnic University, Pomona Presentation for Bioengineering Research In Technical Excellence (BRITE program) 2008

2. Outline  Background  Research Objective  Experimental Approach  Results & Discussion  Conclusion

3. Background  An undesired attachment and accumulation of organisms on surfaces in an aqueous environment  Universal problem  High costs Biofouling is a problem…

4. Biofilm Developmental Process Target

5. Why Colloids? Governing forces: DLVO type: Van der Waals attraction Electrostatic interaction Specific interactions: Electrosteric interaction and hydrophobic interaction, etc. Microorganism Adhesion = Function of solution chemistry, microorganism heterogeneity, substratum heterogeneity, growth phase, hydrodynamic condition, etc.

6. Objectives  How does surface roughness influence the attachment behavior (physical heterogeneity)?  What effects do zeolite coatings have on deposition (chemical heterogeneity)?

7. Experimental Setup

8. Quantifying Colloid Deposition Total flow rate = 2 C o = 2x10 7 * microscope viewing area (204.7 mm × 152.6 mm)

9. Results & Discussion

10. Stainless Steel Comparison Mirror finish unpolished 600-grit polished

11. Aluminum Alloy Comparison unpolished 600-grit polished 1200-grit polished

12. SEM of ZSM-5 coated Al & SS Aluminum AlloyStainless Steel top side

13. Zeta Potential (mV) -54.10 ± 1.54-91.99 ± 2.65-85.66 ± 0.49CML colloids * 25.38 ± 5.54-12.57 ± 0.25 ZSM-5 coating * 45.40 ± 1.454.40 ± 0.69 Stainless Steel * 43.21 ± 1.994.39 ± 0.16Aluminum 100 mM10 mM1 mM * Not available due to the Electro Kinetic Analyzer limitation

14. Colloid Deposition Results in KNO 3

15. Zeta Potential (mV) -54.10 ± 1.54-91.99 ± 2.65-85.66 ± 0.49CML colloids * 25.38 ± 5.54-12.57 ± 0.25 ZSM-5 coating * 45.40 ± 1.454.40 ± 0.69 Stainless Steel * 43.21 ± 1.994.39 ± 0.16Aluminum 100 mM10 mM1 mM * Not available due to the Electro Kinetic Analyzer limitation

16. Colloid Deposition Results in KNO 3

17. Conclusions 1. Surface roughness is a controlling factor on particle deposition at low ionic strength in which system entails a weak electric double layer. 2.The electric double layer dominates the deposition rate at higher ionic strengths and similar surface charges. 3.ZSM-5 coatings decrease deposition rate when compared to bare metal surface counterparts at low ionic strength.

18. Acknowledgements  Dr Sharon Walker  Gexin Chen  Jun Wang  National Science Foundation  UCR Bacterial Adhesion Research Laboratory members (Amy, James)  Rajwant S. Bedi  Thanks to Dr. Yushan Yan for provision of zeolite coated surfaces