How to walk on water and survive bullet

How to walk on water and survive bullet impacts? Rheology of complex fluids and simulated polymer gels Explore SDSU 2012 Joris Billen Ph. D 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

Wound dressings Contact lenses 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