How to walk on water and survive bullet impacts?

Rheology of complex fluids and simulated polymer gels

Explore SDSU 2012Joris 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: ElasticTemporary 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 thinning

shear thickening

How to walk on water?

viscosity

Shear thickening

How to survive bullet impacts?

viscosity

Shear thickening

Shear thinning

viscosity

Polymer = repeating units of monomers

Polymers

Associating polymer gels

Reversible NetworkPolymer chains in a solvent

Rheological response gel

Shear rate

Vis

cosi

ty

[J.Sprakel et al., Soft Matter (2009)]

NewtonianShear thickening

Shear thinning

ApplicationsWound dressings

Cartilage replace-ment / implants

Contact lenses

Actin filaments

Paintball fill

Injectable gels

Controlled drug delivery

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

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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 networksimilar to robustcomputer networks

Thank you for your attention!

Non-Newtonian Dubstep