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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
Andrea Manca 3
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
Andrea Manca 4
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
Milan, 10/15/2013
-8
-4
0
4
8
12
0 0.1 0.2
a / R
Interaction Potential
Andrea Manca 4
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
Milan, 10/15/2013
T
salt[c]
Fractals
Andrea Manca 5 Milan, 10/15/2013
Leaf Venation
Snowflake Cauliflower
Lightning
SCALE INVARIANCE
DLCA Diffusion Limited Cluster Aggregation
RLCA Reaction Limited Cluster Aggregation
Fractal Aggregates
Andrea Manca 6
fd
gg RRM )(
fd
g ttR/1
)( t
g etR )(
),()(3
cgc
d
gg RRfRR f
Milan, 10/15/2013
*
0 0( , ) ( ) Re ( ) ( , )
SI r t I r E r E r t
Scattering Techniques
Andrea Manca 7
( , ) ( , )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
Andrea Manca 8 Milan, 10/15/2013
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
Andrea Manca 11 Milan, 10/15/2013
Why in Microgravity?
Andrea Manca 12 Milan, 10/15/2013
• 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
Andrea Manca 13
S. J. VEEN et Al, Phys. Rev. Lett. 109, 248302 (2012)
Milan, 10/15/2013
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
Milan, 10/15/2013 Andrea Manca 14
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
Andrea Manca 15
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
Andrea Manca 16 Milan, 10/15/2013
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
Andrea Manca 17
Submitted to Phys. Rev. Lett.
Milan, 10/15/2013
),(3
cgc
d
gg RRfRR f