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Dye droplet. mica. Nano film spread. mica. d. h. Film spread. L. - PowerPoint PPT Presentation
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Engineered Molecular FluidicsNSF NIRT Grant 0609087
PIs: S.S. Sheiko1, K. Matyjaszewski2, M. Rubinstein1, O. Velev3
1University of North Carolina at Chapel Hill, 2Carnegie Mellon University, 3North Carolina State University
Constrained spreading of a molecular brush
mNS1/2
m > NS1/2 – un-stretched molecule (same as spreading of linear chain)
1/N
NS < m < NS1/2 – stretched backbone, un-stretched side chains
NS
NS/m21/(NS)
m < S-1/4 – saturated lower layer and appearance of the cap
(NS)1/3 < m < NS – stretched backbone and side chains
(NS)1/3
(NS/m)1/2/m1
S-1/4
S-1/4 < m < (NS)1/3 – fully stretched backbone and H ~ S-1/2
NS/m3NS7/4
Tension energy per backbone monomer Fbb/(mkT)
Concept and methodology
Nb
L
mb
d
H
NbA
H
SNb
kT
F2
2
2
2
3
33
Free energy per side chain @ constant volume HhL=Nb3
hL
d
spreading disjoining backbonestretching
side chainstretching
N
md
L
As alternative to (a) closed-channel systems, we study (b) open structures, where monolayer masses, residing on a substrate, are moved and configured by an external force.
Advantages• smaller volume and direct accessibility • dynamically configurable flow control • rapid heat exchange • substrate-mediated mixing, orientation, and shape of macromolecules
Electric field manipulation of thin films
EOF
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-++ +----
Forward bias
reverse bias
100 μm
Liq
uid
rese
rvo
ir
Film spread
mica
No bias
Forward bias
Forward bias
mica
mica
Molecular water equilibrium film
Liquid reservoir
Film spread
Thin wetting film spreading by electro-osmosis
0 5 10 15 20 25 30 35 40
0
100
200
300
400
500
600
700
800
Me
nis
cus
Dis
pla
ce
men
t (
m)
Time (sec)
25 V/cm 50 V/cm 75 V/cm 100 V/cm 200 V/cm 300 V/cm
0 50 100 150 200 250 3000
20
40
60
80
100
120
Sp
eed
of
Men
iscu
s (
m/s
ec)
Electric Field (V/cm)
0 100 200 300 4000
1000
2000
3000
4000
5000
Mo
bili
ty (
(m
2/ V
se
c)
Electric Field (V/cm)
eof
μeof : standard electroosmotic mobility
ε : permittivity ~ (80)·(8.85 × 10-12 F/m)
ζ : zeta potential of mica ~ - 80 mV
η : viscosity ~ 9x10-4 Pa·sec
= 5.7 x 104 μm2/ V·sec
mica
Dye droplet
mica
Nano film spread
Time
Film spread
Manipulating of molecular fluorophore in a thin film
Flow-induced molecular fractionation
Reservoir
Film
Flow
0 100 200 300 400
0.00
0.05
0.10
0.15
0.20
0.25
Fra
cti
on
Molecular Length (nm)
Distance from Drop 350 m 400 m 440 m 460 m 480 m 500 m
100 200 300 400 500
40
60
80
100
120
Av
era
ge
Le
ng
th (
nm
)
Distance From Drop, m
Mike Barrett, Frank Sun, and David ShirvaniantsJairus Kleinert, Sejong Kim
Katya Zhulina and Gregory Randall
Molecular conformation within 2-D asymmetric mixtures
100 101 102 103 104 105
30
40
50
60
70
NB
RA ,n
m
NA = 1240
NA = 1160
NA = 1080
NA = 1000
NA = 920
NA = 840
NA = 760
NB=11 NB=322
NB=102
NB=24 NB=1766
NB=8813
Phys. Rev. Lett. 99, 137801 (2007)
Andrey Dobrynin and Frank Sun
heterogeneous substrates
RA
𝑅𝐴≈ 𝑏𝑁𝐴3/4𝑁5/4𝑁𝐵−1/4
Molecular visualization: - size, shape, and ordering, - diffusion, mixing, and reactions
constrained
unconstrained
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