how to walk on water and survive bullet impacts? rheology of complex fluids and simulated polymer...

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