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 thickening Shear thinning Newtonian Viscosity Shear rate [J.Sprakel et al., Soft Matter (2009)]
Applications Contact lenses Wound dressings Paintball fill Cartilage replace-ment / implants Actin filaments Controlled drug delivery Injectable gels Self-healing materials
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.