Acoustic atomic force...

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Acoustic atomic force

microscopy

Dr. Ari Salmi

12.2.2014 1


Revisit to resonances

(lecture #3)

12.2.2014

Matemaattis-luonnontieteellinen tiedekunta /

Henkilön nimi / Esityksen nimi 2

• 2008: 0.29 zg resolution

• Chaste et al., Nature Nanotechnology 2012

• Based on a resonating carbon nanotube (f = 2 GHz)

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Even more precise nanoparticle

weighing

• Xe atoms added resonance frequency changes

• 1.7 yg (yoctogram) resolution!

• Mass of proton

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Even more precise nanoparticle

weighing

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Resonances in fullerenes?

• Very little research on resonances in fullerenes

• However... Giannopolous, Physica E 2014

• Fullerenes as mass sensors?

‒ Computational study

5 Å

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• Problem with fullerenes – very high frequencies

5 Å

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• Problem with fullerenes – very high frequencies

5 Å

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• Could perhaps be used as mass sensors

• Ma = 1.9943*10-23 g ~ 20 yg (yoctograms)

• Sensitive up to 0.1 ma = 2 yg!

5 Å


Revisit to actuation

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How fast is Brillouin cooling?

• Equation for the effective temperature has no time

dependency

5 Å

Stokes scatteringAnti-stokes scattering


Elasticity

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Physics: Static elasticity

• Static modulus of elasticity in an isotropic case:

Stress/strain

• The system also ’thins’ when extended

• Poisson ratio

• Shear modulus = ’elastic modulus in shearing’

5 Å

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Physics: Elasticity

• Determined by the elastic tensor

• In general form, stress is related to strain by the

stiffness tensor

• Due to symmetricity of the tensors, 36 elements in

the stiffness tensor

• Voigt notation

5 Å

1

2

3

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Physics: Elasticity

• Symmetries reduce the components

• Orthothropic: 9 components

5 Å

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRHFEL5-uTNB27T-3sjpDNDP0BZi4nX8WY9lf9G_6pAYHN2338p

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Physics: Elasticity


• Cubic: 3 components

5 Å

http://www.ndt.net/article/brown/cubic.gif

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Physics: Elasticity


• Isotropic materials: 2 components

5 Å

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Physics: Dynamic elasticity

• Elasticity under vibratory conditions

• Arises from viscoelasticity

• = phase lag between stress and strain

• Storage modulus

• Elastic portion, stored energy

• Loss modulus

• Viscotic portion, energy lost in heat

5 Å

http://www.continuummechanics.org/cm/images/stress-strain-sines.png


Atomic force microscopy

12.2.2014



• A technique to scan the nanoscopic properties of a

surface

• Based on a contacting tip that is attached to a cantilever

that bends according to the surface features

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What is atomic force

microscopy?

• Contact and non-contact modes

• ’Contact’ mode

‒ Repulsive forces due to exchange interactions

• ’Non-contact’ mode

‒ Attractive forces due to van der Waals interactions

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What is atomic force

microscopy?

http://hone.mech.columbia.edu/wiki/lib/exe/detail.php?id=wiki%3Aatomic_force_microscope&me

dia=wiki:lennard-jones.jpg

• The tip is repulsed cantilever bends surface

features

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Contact mode AFM

• Example image

‒ Carbon nanotube bucky paper

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Contact mode AFM

http://www.nrel.gov/pv/measurements/atomic_force.html

• September 2013: First LEGO AFM

• University College of London

• Based on Arduinos, piezo stages and LEGO bricks

‒ Some structures 3D-printed

‒ Total cost ~500$

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AFM itself is quite old news...


Dynamic AFM

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• The tip is driven with a oscillation frequency

• The properties of the oscillation change as a function of

surface features

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Non-contact mode AFM

(dynamic AFM)

• Gross et al., Science 2009

• Based on a quartz tuning fork design of Giessibl,

APL 2000

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NC-AFM of molecules

• A repulsive force acts on the upper prong

• causes surface charges which are collected by the

metal electrodes

‒ No optics required

• Measures the change in the resonant frequency from

the displacement

• Base resonance frequency 23165 Hz

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NC-AFM of molecules

• Idea: Modify the gold AFM tip by picking up a CO

molecule that attaches to the tip

• Significantly enhances the force (frequency) resolution

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NC-AFM of molecules

• Results: Imaging of pentacene molecular structure!

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NC-AFM of molecules

• De Oteyza et al., Science 2013

• Similar functionalization of tip with an CO molecule

• Imaging of chemical reactions!

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NC-AFM of chemical reactions

• Ashino et al., PRL 2009 and Ashino et al., Nature

Nanotechnology 2008

• Measurement of the damping of the AFM vibration

• CNT ’peapod’ structures

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Damping force spectroscopy

• Damping of AFM vibrations (f = 159 kHz, A = 21 Å)

• At point A (approaching cantilever), abrupt change to

point B

• When retracting, similar abrupt change from C to D

‒ Compensation forces of the cantilever and substrate

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• The vibrations lose energy when they are close to

the ’peas’

• Not exactly on top, though

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• SWCNT’s, diameter 16.2 ± 0.5 Å

• Filled with metallofullerines (Dy@C82), d = 8 Å

• Empty tube shows very little damping (characterized

by energy loss in meV) (1 and 5)

• Tube with metallofullerines features damping

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• When the tube diameter is decreased to 15 ± 0.5 Å

(3 and 7) or 13 ± 0.5 Å (4 and 8), the damping

increases

• 4 appears thicker due to surface undulation

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Dynamic AFM and charge

distributions

• Mohn et al., Nature Nanotechnology 2012

• LCPD (local contact potential difference)

• Try to minimize the frequency shift

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Dynamic AFM and charge

distributions

• A LCPD image of naphthalocyanine

5 Å

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Multiharmonic atomic force

microscopy

• Raman et al., Nature Nanotechnology 2011

• Drive the cantilever with one frequency, listen to the

harmonics

5 Å

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Multiharmonic atomic force

microscopy

• Measurement on in vivo rat fibroblast cells

• Determine both storage and loss moduli

5 Å

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AFM nanomechanical

multifrequency force spectroscopy

• Herruzo et al., Nature Communications 20.1.2014

• Tip vibrates and is in contact with the sample

• Multimode use higher order cantilever resonances

• Keep the first mode amplitude and frequency shift

constant (change the excitation)

• Keep the second mode amplitude constant

‒ quantitative determination of elasticity and viscosity!

5 Å

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AFM nanomechanical


• The results obtained for known materials match

well with theoretical predictions

• Should yield a straight line

5 Å

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AFM nanomechanical


• Results: Calibration

• LDPE (nominal E = 0.1 GPa) embedded in PS (nominal

E = 2 GPa)

5 Å

750 nm

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AFM nanomechanical


• Results: Block co-polymer (PS embedded in PMMA)

• Results compare very well with prediction

‒ Nominal MOEs agree

‒ Scale bar 100 nm

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Scanning Near-field ultrasonic

holography (SNFUH)

• Shekhawat et al., Science 2005

• A technique that allows sub-surface

characterization

• Based on two ultrasonic transducers and

dynamic AFM

• The two transducers form an acoustic standing

wave

• The perturbation of the standing wave is measured

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holography (SNFUH)

• Results: Validation

• Model nanoparticle system (Polymer-gold

nanoparticle-polymer-silicon)

• Nanoparticles clearly visible

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holography (SNFUH)

• Results: 2nd test system

• Polymer-SiN-Polymer structures

• Detected voids at the SiN-polymer interfaces

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holography (SNFUH)

• Results: Detection of malaria infection in red blood

cells

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holography (SNFUH)

• Tetard et al., Nature Nanotechnology 2008

• Detection of single walled carbon nanohorns

(SWCNHs) inside cells

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holography (SNFUH)

• Carbon nanoparticles still clearly visible in mice

lungs after a week

• Not detected with normal AFM

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holography (SNFUH)

• Also in red blood cells


Take-home

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Take-home: Acoustic atomic

force microscopy

• A method of determining (in nanoscale)

• Sub-surface features

• Elasticity

• Viscosity

Acoustic atomic force...

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