1. How to walk on water and survive bullet impacts? Rheology of complex fluids and simulated polymer gels Explore SDSU 2012 Joris Billen PhD Candidate Computational Science San Diego State University & Claremont Graduate University Supervisor: Prof A. Baljon, Department of Physics (SDSU)

2. What is a complex fluid? Complex fluids are everywhere: Kitchen (chocolate, mayonaise, milk, ketchup) Human body (blood, mucus) Products (Cosmetics, liquid crystals, Shaving cream) Fluids showing non-linear viscous behaviours, as well as viscoelastic materials, are Complex Fluids. But …what is non-linear viscous and viscoelastic behavior?

3. Visco-elastic behavior After application of a stress… Permanent deformation: Viscous Restores initial configuration: Elastic Temporary restoration: Visco-elastic Tendons, ligaments, polymers, toothpaste, gels,…

4. Non-linear viscous behavior: Newtonian VS non-Newtonian? Slope= viscosity

5. Non-linear viscous behavior: Newtonian VS non-Newtonian? shear thinning shear thickening

6. How to walk on water? viscosity Shear thickening

7. How to survive bullet impacts? viscosity Shear thickening

8. Shear thinning viscosity

9. Polymer = repeating units of monomers Polymers

10. Associating polymer gels Reversible Network Polymer chains in a solvent

11. Rheological response gel Shear rate Viscosity [J.Sprakel et al., Soft Matter (2009)] Newtonian Shear thickening Shear thinning

12. Applications Wound dressings Cartilage replace- ment / implants Contact lenses Actin filaments Paintball fill Injectable gels Controlled drug delivery Self-healing materials

13. So … what do you do all day?

14. Modeling the physics of a polymer gel

15. Computer simulations of polymer gels 1000 polymer chains of 8 beads long However …we don’t work with pictures but with files of -coordinates of atoms -connections in network

16. Computer simulations of polymer gels Calculate properties that are impossible to measure experimentally 5 4 6 3 3 2

17. Our work on the cover of a magazine J. Billen, M. Wilson, A. Rabinovitch, A. R. C. Baljon, Europhys. Lett. 87 (2009) 68003. Structure gel network similar to robust computer networks

18. Thank you for your attention!

19. Non-Newtonian Dubstep