Max Planck Institute for Polymer Research
Confocal imaging of shear deformation in aggregated colloidal
systems
Jennifer Wenzl, Marcel Roth, Günter K. Auernhammer
PiKo-Workshop, Mainz 29.-30. 09. 2011
Max Planck Institute for Polymer Research 2
• Project • Used system
– Particles – Structure
• Experiment – Measurement – Data analysis
• Shear Data – One step – Quasi-continuous
• Rotation
Jennifer Wenzl
Max Planck Institute for Polymer Research 3
Project
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Max Planck Institute for Polymer Research 4
PiKo-project
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PiKo-project: „B3 -Deformation, Rollen und Gleiten von Partikeln und Partikelagglomeraten“
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Our aim
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How do shear zones arise?
Is restructuring of aggregates dominated by rolling or sliding?
How is the (rolling) friction affected by surface roughness?
How does a colloidal gel reorganize under shear?
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Used system
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Particles
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Polydisperse silica (~7µm)
Realizing sands & grains
Raspberries (~470nm)
Monodisperse silica (~750nm)
Particles: D. Vollmer
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Sample systems
Jennifer Wenzl
Depending on preparation (surface properties & solvents) different structure types can be realized:
Loose network
Densely packed beds 3-phase system
• Hydrophobic • Organic solvent
(cis-decaline) • Interaction via
carbon-chains
• Hydrophobic (compaction via drying)
• Hydrophilic (weak interaction)
• 2 non-miscible solvents • Hydrophobic or
hydrophilic • One solvent fluorescent
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Experiment
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Confocal microscopy
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Structure with 3D imaging
Fluorescently labeled particles required
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Shear geometry
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Inducing rotation: applying shear displacement
Displacement of upper plate (max. 160µm): • In x-y-plane (glass plate) • In x-z-plane (Flat-Top-indentor tip)
Different plate materials & adjustable surface properties
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Shear geometry
Jennifer Wenzl
Inducing rotation: applying shear displacement
Displacement of upper plate (max. 160µm): • In x-y-plane (glass plate) • In x-z-plane (Flat-Top-indentor tip)
Different plate materials & adjustable surface properties
fluorescent mode + reflective mode 100µm
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Data analysis
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Filtering: combination of raw image with mask
maximum of filtered intensity
Sectioning of raw image
How to find polydisperse particles – Step 1
Crocker, Grier, J. Coll. Int. Sci. (1996) 179, 298
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Data analysis
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How to find polydisperse particles – Step 2
Localization in 3D
Filtered image
extension analysis
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Data analysis
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How to find polydisperse particles – Step 3
computer reconstruction X
Z
Y
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Shear data
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One step shear
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• Used system: small hydrophobic particles (750nm) in cis-decalin • Shear displacement: 5µm in x-direction (< 100 ms)
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One step shear
Jennifer Wenzl
• Used system: small hydrophobic particles (750nm) in cis-decalin • Shear displacement: 5µm in x-direction (< 100 ms)
low z (near lower plate): displacements in x- & y-direction, additionally cluster rotation
high z-position (near upper plate): only displacement in x-direction
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Quasi-continuous shear
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• Slow step-wise shear displacement in x-direction • Maximum shear amplitude: 56µm • Measurement every 2µm of indentor tip displacement
z-position [µm]
• Used system: large hydrophilic particles (~7µm) in NaSCN-solvent
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Quasi-continuous shear
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0
28
# m
easu
rem
ent
Particle displacements over whole sample in all directions
-6 -5 -4 -3 -2 -1 0 1 2 3
0
10
20
30
40
z-p
ositio
n [
µm
]
displacement x [µm] 0 1 2 3 4 5 6 7
0
10
20
30
40
displacement all [µm]
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Quasi-continuous shear
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-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8
0
10
20
30
40
displacement y [µm]
y [µm] Top View
y
Shear displacement (x-direction)
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Comparison
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Small hydrophobic particles Large hydrophilic particles
+ High interaction (network)
Small & monodisperse
+ Large & polydisperse
Low interaction (almost hard spheres)
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Rotation
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Rotation of single particles
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partial bleaching of dyes with polarized laser
Particles appear spherical
Fluorescence intensity depends on angle between laser & dye
Lettinga et al., J. Chem. Phys. (2004) 120, 4517 & Roth, et al., Arxiv cond-mat.soft (2011) 1106.3623v1
rel. inte
nsity
Polarization anisotropy
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Outlook
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• Increasing interaction in system with large particles (loose gel /network structure)
• Bleaching of few particles (via polarization or intensity anisotropy)
• Determination of the rotational motion of the particles • Shearing of 3-phase system
Next steps:
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• Thanks to:
• Günter K. Auernhammer
• Hans-Jürgen Butt
• Doris Vollmer, Lena Mammen, Gabriele Schäfer
• Marcel Roth, Daniela Fell, Miao Wang
Jennifer Wenzl
Max Planck Institute for Polymer Research 27 Jennifer Wenzl
Thank you for your attention
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Additional slides
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Collaboration projects
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D7 – Entwicklung und Charakterisierung der Struktur gescherter kohäsiver Schüttgüter
• Shearing of densely packed beds
• Observation of trajectories and rotational motion of particles
B8 – Mechanische Eigenschaften dichter granularer Schüttungen in Gegenwart benetzender Flüssigkeiten
• 3-phase-system: particles & 2 non-miscible solvents
• Tuning particle surface & solvent mixture to change wetting behavior
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... and beyond
Jennifer Wenzl
Intensity anisotropy
+ Only intensity information
+ Cross position easy to detect
+ Both rotation angles f & Q
‒ Hard to bleach one single particle
‒ Bad intensity resolution
‒ Automized data analysis required
