The nanomechanics of Compositional Mapping by Amplitude Modulation AFM

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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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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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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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



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>

The nanomechanics of Compositional Mapping by Amplitude Modulation AFM

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