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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)
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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?
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Visco-elastic behavior
After application of a stress…
Permanent deformation: Viscous Restores initial configuration: ElasticTemporary restoration: Visco-elastic
• Tendons, ligaments, polymers, toothpaste, gels,…
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Non-linear viscous behavior: Newtonian VS non-Newtonian?
Slope=viscosity
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Non-linear viscous behavior: Newtonian VS non-Newtonian?
shear thinning
shear thickening
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How to walk on water?
viscosity
Shear thickening
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How to survive bullet impacts?
viscosity
Shear thickening
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Shear thinning
viscosity
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Polymer = repeating units of monomers
Polymers
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Associating polymer gels
Reversible NetworkPolymer chains in a solvent
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Rheological response gel
Shear rate
Vis
cosi
ty
[J.Sprakel et al., Soft Matter (2009)]
NewtonianShear thickening
Shear thinning
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ApplicationsWound dressings
Cartilage replace-ment / implants
Contact lenses
Actin filaments
Paintball fill
Injectable gels
Controlled drug delivery
Self-healing materials
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So … what do you do all day?
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Modeling the physics of a polymer gel
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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
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Computer simulations of polymer gels
Calculate properties that are impossible to measure experimentally
54
6
3
32
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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
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Thank you for your attention!
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Non-Newtonian Dubstep