DYNAMICS OF COLLOIDAL AGGREGATION IN MICROGRAVITY BY CRITICAL CASIMIR FORCES

Milan, 10/15/2013 Andrea Manca

Milan, 10/15/2013 Andrea Manca 1

Timeline Theory of Casimir Effect

Theory of Critical Casimir Effect

Experimental observation of Casimir Effect

Experimental observation of Critical Casimir Effect

Colloidal aggregation induced by Critical Casimir Effect

COLLOID: first run

COLLOID: second run

Advanced Colloid Experiment

1948 1978 1997 2008 2009 2010 2011

2012-2015

Bottom-Up Approach

My PhD

2014

Water & Lutidine (T ≈ 34°C)

Lutidine + Water

Phase Diagram

Milan, 10/15/2013 Andrea Manca 2

C. HERTLEIN et Al, Nature 451, 136-137 (2008)

63.0

0 1

cT

T

/3

LL

Tk

A

F B

Critical Casimir Effect

Fraction of 3MP in water

Tem

pera

ture

2 phases

1 phase

water

3MP

3MP

+

water

Cc

Colloidal

aggregation

Solvent Phase Diagram

Phase Separation

Line

C0 = 37.5% Tagg = 46.2°C

•Water •3-methyl Pyridine •NaCl •SiO2 Spheres 0.2 µm in radius

Analyzed Sample

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D. BONN et Al, Phys. Rev. Lett. 103, 156101 (2009)

Milan, 10/15/2013

-8

-4

0

4

8

12

0 0.1 0.2

a / R

Interaction Potential

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Index Matching

a

- - -

-

-

- - -

U / kT

- - -

-

-

- - -

R

D. BONN et Al, Phys. Rev. Lett. 103, 156101 (2009)

CasimirVdWel VVVrV )(

da

del eaV /2)(

/1)( a

Casimir eaV

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-8

-4

0

4

8

12

0 0.1 0.2

a / R

Interaction Potential

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Index Matching

a

- - -

-

-

- - -

U / kT

- - -

-

-

- - -

R

Salt Concentration Temperature

D. BONN et Al, Phys. Rev. Lett. 103, 156101 (2009)

CasimirVdWel VVVrV )(

da

del eaV /2)(

/1)( a

Casimir eaV

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T

salt[c]

Fractals

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Leaf Venation

Snowflake Cauliflower

Lightning

SCALE INVARIANCE

DLCA Diffusion Limited Cluster Aggregation

RLCA Reaction Limited Cluster Aggregation

Fractal Aggregates

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fd

gg RRM )(

fd

g ttR/1

)( t

g etR )(

),()(3

cgc

d

gg RRfRR f

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*

0 0( , ) ( ) Re ( ) ( , )

SI r t I r E r E r t

Scattering Techniques

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( , ) ( , )q t I q t

Low Angle Light Scattering Dynamic Light Scattering

Near Field Scattering In-Line Holography

),( tqI

I(q)

q

n(q)

k0

kS

1

q

Milan, 10/15/2013

LALS

DLS

DLS

LALS

6

Bk T

DR

DLS

),( tqI

6

Bk T

DR

COLLOID

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September-October 2010 October-November 2011

25 µm

Holographic reconstruction

Static Form Factor

Laser: 935 nm (IR) Sample: Water, 3-methyl Pyridine, NaCl, SiO2 Spheres 0.2 µm in radius. Objective: 20x, NA 0.25 CCD: 1024x1024, 6.6 µm

Advanced Colloid Experiment

Andrea Manca 9

2m

2014: ACE at ISS

• Microscopy ? Near field Scattering ? Holographic reconstruction

Milan, 10/15/2013

Advanced Colloid Experiment

Andrea Manca 10 Milan, 10/15/2013

Ground Based Measurements

Confocal Microscopy Near Field Scattering: Statics and Dynamics

In-Line Holography

COLLOID: • Evidence of T-dependent interaction • Information on the Internal Structure • Analysis of COLLOID 2

ACE:

• On Ground: characterization of single particles and aggregates

• On ISS: study of the aggregation processes and of the aggregate structure in perfect DLA conditions

Summary and Perspectives

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Why in Microgravity?

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• Higher density fluctuations • No convection • No settling or buoyancy • Slow DLA process

/ 22

( 0)( )

2( )1

3

fd

g

f

I qS q

qR

d

Fisher-Burford

200 s

700 s

2100 s

Static Form Factor

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S. J. VEEN et Al, Phys. Rev. Lett. 109, 248302 (2012)

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2( , )( , )

d q tDq q t

dt

2

( ) ( ) DqE t E t Ae B

( , ) ( , )q t I q t

t

q=0.3 µm-1

q=0.7 µm-1

q=1 µm-1

q=1.75 µm-1

Dynamic Light Scattering

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2 2

( ) 311 1

2 3 2( )

eff f

f g

D q d

D d qR

2( )( ) ( ) effD q q

E t E t Ae B

Dynamic Light Scattering Results

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M. Y. LIN et Al, Phys Rev A 41, 2005 (1990) M. LATTUADA et Al, Langmuir 20, 5630 (2004)

( ) ( )eff Rot

D q D q D 0.5 1.0 1.5 2.0 2.5

0.2

0.1

0.1

0.2

0.5 1.0 1.5 2.0 2.5

0.2

0.1

0.1

0.2

0.5 1.0 1.5 2.0 2.5

0.2

0.1

0.1

0.2

Milan, 10/15/2013

2 2

311 1

2 3 2( )

eff f

f g

D d

D d qR

β=1.05

β=0.82

Dynamic Light Scattering Results

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Tagg+ 0.0 Tagg+ 0.1 Tagg+ 0.2 Tagg+ 0.3 Tagg+ 0.4

( , ) ( )c c c

f R R R R

2

( , ) cR R

c cf R R e

( , ) cR R

c cf R R e

Structure of the Aggregates

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Submitted to Phys. Rev. Lett.

Milan, 10/15/2013

),(3

cgc

d

gg RRfRR f