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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) 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? Visco-elastic behavior After application of a stress… Permanent deformation: Viscous Restores initial configuration: Elastic Temporary restoration: Visco-elastic • Tendons, ligaments, polymers, toothpaste, gels,… Non-linear viscous behavior: Newtonian VS non-Newtonian? Slope= viscosity Non-linear viscous behavior: Newtonian VS non-Newtonian? shear thickening shear thinning How to walk on water? viscosity Shear thickening How to survive bullet impacts? viscosity Shear thickening Shear thinning viscosity Polymers Polymer = repeating units of monomers Associating polymer gels Polymer chains in a solvent Reversible Network Rheological response gel Shear thinning Viscosity Newtonian Shear thickening [J.Sprakel et al., Soft Matter (2009)] Shear rate Contact lenses Wound dressings Paintball fill Applications Cartilage replacement / implants Actin filaments Controlled drug delivery Injectable gels Self-healing materials So … what do you do all day? Modeling the physics of a polymer gel 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 Computer simulations of polymer gels Calculate properties that are impossible to measure experimentally 6 3 2 3 5 4 Our work on the cover of a magazine Structure gel network similar to robust computer networks J. Billen, M. Wilson, A. Rabinovitch, A. R. C. Baljon, Europhys. Lett. 87 (2009) 68003. Thank you for your attention! Non-Newtonian Dubstep