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8/7/2019 The nanomechanics of Compositional Mapping by Amplitude Modulation AFM
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Laboratorio de Fuerzas y TLaboratorio de Fuerzas y Tnelnel
Instituto de Microelectrnica de Madrid
Ricardo Garca
Frontiers of SPM, 5 Oct. 2006
Outline
i). Forces and molecular resolution
ii). The physics of phase Imaging:elastic vs. Inelastic processes
iii). Identification of energy dissipation
Quantitative information
iv). Enhancing Force Sensitivity: Beyond1st mode Imaging
v). Summary
The nanomechanics ofCompositional Mapping byAmplitude Modulation AFM
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Laboratorio de Fuerzas y TLaboratorio de Fuerzas y Tnelnel
Instituto de Microelectrnica de Madrid
10 nm
a
GroEL in liquid, T. Ando et al. PNAS 98, 12468 (2001)
PM in liquid, D.J. Muller et al.Biophys. J. 77, 1150 (1999)
50 nm
IgG, SanPaulo, Garcia, Biophys.J. 78, 1599 (2000)
8 nm
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Laboratorio de Fuerzas y TLaboratorio de Fuerzas y Tnelnel
Instituto de Microelectrnica de Madrid
verified values
Medium Force (pN) Forcesensitivity
Resolution*
(nm)
Air IgG 300 0.1 3
Liquid 1 PMcrystal
100 0.05 1.1
Liquid 2GroEL patches
No available No available 2
Process Force (pN) length scale
DNA entropicelasticity
0.01-10 0.8 L
DNA intrinsicelasticity
10-70 0.8-1 L
Proteinunfolding
15-50 3-5 nm
Some forces in molecular biology
Forces and Resolution in AM-AFM (biomolecules)
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/0
SIMULATION
R= 10 nm, A0=10 nm, zc=8 nm,
E=1 GPa, k=40 N/m, f0=325kHz
Free oscillating tip (10 nm ) Interacting tip (10 nm size )
Mechanics of vibrating
nanosystems:
Coexistence of oscillationstates: Bi-stability
AS Paulo, R Garca, PRB 66, 041406(R) (2002)
Resonance Curves
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0
2
4
6
8
10
-1.0
-0.5
0.0
0.5
1.0
0 2 4 6 8 10 12
0.0
0.5
1.0
(a)
High amplitude solution
Low amplitude solutionAmplitude(nm
)
(b)
(nN)
(c)
Contacttime
Tip-surface separation (nm)
Simulation data: R=20 nm
f0=350 kHz, Q=400,
H=6.4x10-20, E*=1.52 GPa
0
45
90
135
180
Phase(deg)
H
L
6 9 12 15 18 21 24
6
9
12
15
18
Amplitude(nm)
z piezo displacement (nm)
40 nm
H
L
Garcia, San Paulo, PRB 61, R13381 (2000);Garcia, Prez, Surf. Sci. Rep. 47, 197 (2002)
simulationsExps.
H and L states have
different properties
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Driving signal:F(t) = F0cos(wt)
The dynamic response of the cantilever is modified by thetip-surface interactions
Laboratorio de Fuerzas y TLaboratorio de Fuerzas y Tnelnel
Instituto de Microelectrnica de Madrid
Phase Imaging
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Topography Phase Image
Wood pulp fiber, D.A. Chernoff (1995)
1 m
c
2 m2 m
b
S. Typhimurium cells, R. Acvi, Biophys. J. (2006)
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10 nm
a
GroEL in liquid, T. Ando et al. PNAS 98, 12468 (2001)
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Polymer morphology and structure as a
function of temperature. Hydrogenated diblock
copolymer (PEO-PB). Crystallisation of PEO
blocks occurs individually for each sphere
(light are crystalline, dark amorphous). Reiteret al., Phys. Rev. Lett. 87, 2261 (2001) Phase Image,
size 1m2
Topography Phase Image
Polymers: Morphology and Structure
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PHASECONTRAST
ELASTICCONTRIBUTIONS
INELASTICCONTRIBUTIONS
TOPOGRAPHIC EFFECTS
TAPPING NON CONTACTTRANSITIONS
VISCOELASTICITY
ADHESION HYSTERESIS
CAPILLARY FORCES
HIDROPHILIC/HIDROPHOBICINTERACTIONS
YOUNG MODULUS(In presence of dissipative channels)
Sources of Phase Imaging Contrast
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+>>z0The virial theorem applied to the tip allows to deduce
0
2cos
AAk
zFQ
c
ts>