AFM

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Asylum Research

Nanoscale mechanical properties are a key consideration in many applications.
Oxford Instruments Asylum Research offers a variety of complementary AFM techniquesin our NanomechPro™ Toolkit that let you measure everything from cells to ceramics.
This collection can accurately evaluate a wide range of nanomechanical behavior including
viscoelastic properties, adhesive forces, and hardness. The multiple techniques offer greater
flexibility for different applications and allow deeper insight through comparison of results.

Introduction

DYNAMIC MODESQUASISTATIC MODES

Nanoscale mechanical properties impact the behavior andperformance of countless materials and help inform both
our theoretical understanding of these materials and theirdevelopment for commercial applications. Examples can befound in many disciplines, for instance in materials science,
where elastic modulus affects the reliability of nanoporous
dielectric films in semiconductor devices, and in biology,
where relations have been observed between viscoelastic
damping and the metastatic potential of cancer cells.
As we continue to learn more about the critical role ofnanomechanics, our need for techniques that more

fully measure nanoscale mechanical properties grows
in importance. The atomic force microscope (AFM) has
powerful capabilities for nanomechanical characterization
due to its inherent spatial resolution and force sensitivity.
However, the sheer diversity of materials’ properties
prevents any single AFM technique from providing
the most relevant or accurate data for every application.
The NanomechPro Toolkit was developed to address
this issue. It contains a collection of AFM techniquesthat meet a broad spectrum of nanomechanicalcharacterization needs (Table 1).

Techniques in the
NanomechPro Toolkit

Elastic Modulus
Range

Force Curves / Force
Volume Mapping●●●●●●●○○

No

~3 hr
(6 Hz ramp rate)○●●●●●●●●

No~9 min(300 Hz ramp rate)(1 kHz for Cypher)

Dissipation,
but not directlytan δ~4 min(1 Hz line rate)

No

~10 s
(20 Hz line rate using
small cantilevers)

Rapid and simple. Can provide
enhanced contrast andresolution vs. phase imaging●●●●●●●●●

No

~10 s
(20 Hz line rate using
small cantilevers)

Rapid and simple●●●●●●●●●

Yes

~10 s
(20 Hz line rate using
small cantilevers)

Rapid and simple. Quantifies
loss tangent, simplifying
interpretation of phase data

Quantifies only loss tangent
whenused without full AM-FM Mode○○●●●●●●●

Yes

~10 s
(20 Hz line rate using
small cantilevers)

Rapid and simple. Measuresboth E′ and tan δ

Currently only supports Hertziancontact mechanics○○○○○○●●●

Yes~4 min(1 Hz line rate)

Measures both E′ and E″

Currently only supports Hertziancontact mechanics

Fast Force Mapping

1 kPa – 1 GPa

10 kPa – 100 GPa○○○●●●●○○

Force Modulation
Imaging

1 MPa – 1 GPa

Bimodal Dual AC
Imaging

1 kPa – 100 GPa

Phase Imaging
Loss Tangent
Imaging●●●●●●●●●

1 kPa – 100 GPa

1 kPa – 100 GPa

AM-FM

100 kPa – 100+ GPa

Contact Resonance

1 GPa – 100+ GPa

Loss Modulus / Acquisition time
Loss Tangent(256×256 image)

Advantages

Disadvantages

Many indentation models
supported, including Hertz /Sneddon, DerjaguinMüller-Toporov (DMT),Johnson-Kendall-Roberts (JKR),
Oliver-Pharr

Impractically slow at higher pixel
density

Can measure response
at fixed frequencies overa wide range

Currently only qualitative
analysisin Asylum software

Slower than dynamic modes

Only qualitative contrast.
Can be difficult to interpret.

Table 1: Comparison of techniques as implemented by Asylum Research in the NanomechPro
Toolkit. The approximate elastic modulus range of applicability is shown for each mode, where
the dots represent orders of magnitude in storage modulus E’ from 1 kPa to 100 GPa. Imageacquisition times are given for readily achievable scan or ramp rates and assume the use ofsmall cantilevers for techniques based on tapping mode. Actual speeds may be faster or slower
depending on many factors. Note that AM-FM and Contact Resonance modes are the only
techniques listed that can quantitatively measure both the elastic response (E’) and viscous
response (loss modulus, E” or loss tangent, tan δ).

1

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Force Curves and Force Volume Mapping
Force curves are a well-known quasistatic method to probesurface forces.1 When used in nanomechanical experiments,
they provide quantitative data on elastic modulus, hardness,
and adhesive and van der Waals forces. Force curves are mostsensitive when the cantilever spring constant roughly matches
the stiffness of the tip-sample contact. Thus, they are best
suited to biological and polymeric materials with elastic
moduli of up to a few gigapascals, if standard commercial
cantilevers are used.

Figure 1: Force mapping experiments on chemically unmodified,live cortical neuronal cells to investigate the variation of elasticity
with temperature. (top) Example force curve of a cell at 25ºC (left)and 37ºC (right). The inset images show optical micrographs ofthe cell. (bottom) Histograms of cell elastic modulus obtained from
16 µm ×16 µm force maps. Significant differences in modulus areobserved from 25ºC (blue) to 37ºC (red). Experiments performedin liquid on the MFP-3D AFM with the BioHeater temperature
stage. Adapted from Ref. 2.

Techniques in the NanomechPro Toolkit measure a rangeof mechanical quantities including elastic properties (e.g.,contact stiffness, Young’s modulus, storage modulus E′),
viscous properties (e.g., contact damping, loss modulus Eʺ,loss tangent tan δ), adhesive and van der Waals forces, andhardness. Techniques range from simple qualitative tools tomore sophisticated quantitative methods so that you canchoose the best approach for a given application. Resultsfrom different techniques on the same sample provide
complementary information for enhanced accuracy andcross-checking. As Table 1 on the previous page shows,methods in the NanomechPro Toolkit are applicable tovirtually any material: everything from compliant cells andgels with modulus of only a few kPa to stiff metals andceramics of hundreds of GPa. Many techniques canalso operate with small cantilevers, enabling accurate
measurements at higher speed and lower noise.
Here we discuss several key techniques in the NanomechPro
Toolkit available on both the Cypher and MFP-3D family
AFMs. Techniques are considered either quasistatic (near-DCor low frequency) or dynamic (higher frequency) dependingon the frequency of cantilever actuation and the cantilever’s
characteristic resonant frequency. Interpretation of quasistatic
data for material properties is better known. However,recent advances show exciting progress for highly sensitive,
quantitative measurements with dynamic modes.

2

Force curves are acquired by lowering the base of the AFM
cantilever until the tip makes contact with the sample. This
motion continues, and the tip deforms or indents the sample
until a trigger threshold is reached, such as base displacement
or cantilever deflection. The cantilever is then withdrawn until
the tip loses contact with the sample. The measured cantileverdeflection versus Z sensor position during this load-unload cycle
is converted to a force curve with measurements of the cantileversensitivity and spring constant. Figure 1 shows examples of force
curves acquired on cortical neurons.
Force curves can also be acquired in 2D arrays called force maps
or force volumes. One force map can provide multiple imagesof different properties measured simultaneously, such as elastic
modulus, adhesion, and height. The user specifies the number ofarray points and the location and size of the region of interest.
Each force curve is saved separately for individual analysis.
Although valuable for measuring elastic modulus, conventional
force curve methods do not directly quantify the sample’s viscous
properties. Modifications to the basic force curve techniqueare required for this purpose. For example, creep complianceand stress relaxation measurements can be performed byinserting a hold interval of constant force between the load
and unload segments.3 Similarly, adding a low-amplitude AC
modulation (~5-200 Hz) during the hold segment enables
quantitative measurements of storage and loss modulus.4

Oxford Instruments Asylum Research
AFMs for Force Curves and Force Mappingorce measurements on all Oxford Instruments Asylum• FResearch
AFMs are limited only by Brownian (thermal)
motion. Combined with its ultra-low-noise Z sensors, thismeans that both axes of force curves are measured withthe highest possible sensitivity and accuracy.
is a proprietary software feature that, with a• GetReal™
single click, automatically calibrates the cantilever spring
constant and deflection sensitivity.
he open architecture of the control software on all• TAsylum
AFMs provides exceptional versatility for custom
experiments, and enables advanced force measurementswith powerful capabilities.

AFM

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Asylum Research

Fast Force Mapping Mode
Force volume mapping is a powerful technique forcorrelating functional and structural information. However,
it is inconveniently slow. To address this problem, Oxford
Instruments Asylum Research offers Fast Force MappingMode, which can acquire force curves at pixel rates up to 300
Hz on MFP-3D Infinity™ AFMs, and 1kHz on Cypher family
AFMs. Using a continuous motion from pixel to pixel, insteadof disjointed steps, Fast Force Mapping Mode can capture
a complete array of force curves in just a few minutes. For
example, a 256 × 256 image of standard force curves takes
over 18 h to acquire at 1 s per pixel. By contrast, it takes
less than 10 min with Fast Force Mapping Mode. Suchdramatically reduced acquisition times enable images withhigher pixel density, for improved lateral resolution. Figure
2 shows an image of 1024×1024 pixels, acquired with Fast
Force Mapping Mode on a polymer blend sample, wherefeatures as small as approximately 10 nm are resolved.
In Fast Force Mapping Mode, the entire force curve foreach image pixel is captured and saved with no hidden
data manipulation. Realtime and offline analysis models
can be applied to calculate modulus, adhesion, and otherproperties. Models are fully accessible for user inspection
or modification, if desired. Fast Force Mapping Modeis applicable to samples with a modulus ranging fromapproximately 10 kPa to over 100 GPa, depending on the
choice of cantilever.

GPa
4

2

0

Figure 3: Polystyrene-polypropylene polymer blend thin film
imaged using Fast Force Mapping mode. Elastic modulus isshown on 3D topography, 6 µm scan.

Figure 3 shows elastic modulus overlaid on topography for apolystyrene (PS)-polypropylene (PP) polymer blend spin casted
onto silicon. Imaged with Fast Force Mapping Mode on a
Cypher AFM with 512×512 pixels and a scan size of 6 μm.
The force curves were taken with an amplitude of 80 nm andwere measured at 1 kHz. Notably, every single force curve(deflection vs. height sensor) was collected for the image.
Though a modulus image is calculated and displayed in realtime, the underlying force curve may be readily reanalyzed
with other contact mechanics models (e.g. Hertz, Sneddon,
DMT, JKR, Oliver-Pharr, see next page for details). In this case,the Hertz model was used assuming a punch-shaped indenter.
Compared to the PS-PCL blend shown in Figure 2, themodulus of PS and PP are much closer together (~3 GPa and
2.4 GPa, respectively). Despite the relatively small difference,the contrast is still very clear.

Phase Imaging

Figure 2: (top) Elastic modulus overlaid on topography for a polystyrene(PS)-polycaprolactone (PCL) blend. Imaged with Fast Force Mapping Modeon the MFP-3D Infinity AFM. Image size 4 μm. The 1024 ×1024 pixel image
would be impractically slow to obtain with conventional force volume
techniques. As expected from bulk literature values, PS regions (yellow)
have higher modulus (~3 GPa) than PCL regions (purple, ~350 MPa).
(bottom) Examples of complete force curves acquired during imaging inFast Force Mapping Mode. The curves on PS have higher slope than thoseon PCL, indicating higher modulus.

Since its first demonstration in the late 1990s,9 tapping
mode with phase imaging10,11 has become a valuable
technique because it often provides contrast between
different sample components. The phase response depends
not only on the sample’s mechanical properties (howthe material stores elastic energy and dissipates viscousenergy), but also on other dissipative forces and operationalparameters. Depending on operating conditions, thecontrast can even invert; although this complicates its
interpretation, phase imaging remains widely used because
it is so simple to measure.

3

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Force Modeling
Quantitative data on mechanical properties, including elastic
modulus, hardness, and adhesion, are obtained from AFM
force curves by fitting the experimental data to a modelfor the tip-sample contact.8 The diversity of materials andpossible experimental conditions means that no single
model can correctly apply to all samples. For this reason,
Oxford Instruments Asylum Research software provides avariety of analysis models that offers user-friendly flexibility
and convenience. Various parameters in each model can be
modified from the main software interface. In addition, thesoftware’s open architecture makes all routines accessible forcustomization, if desired.
Models that are preprogrammed in Oxford Instruments
Asylum Research software include:
ertz/Sneddon: This popular model allows the user to• Hchoose
from several tip shapes including hemisphere,
cone, and flat punch. It assumes that the tip-sample
interaction is linearly elastic and does not include theeffects of adhesion or other surface interactions.
ohnson-Kendall-Roberts (JKR): The JKR model is used
• Jwhenthere is strong adhesive contact between the
tip and sample, in addition to the elastic interaction.
Adhesion effects are included inside the contact area
only. JKR is applicable in cases where the tip radius isrelatively large compared to the indentation depth, forinstance with relatively compliant materials.
(DMT): The DMT model is• Derjaguin-Müller-Toporov
useful for samples that have weak but detectableadhesive forces. Attractive interactions such as adhesion
are included outside the contact area only. DMT tends tobe most useful for stiffer samples with low adhesion andwhen the tip radius is relatively small compared to thesample indentation depth.
This model is used when the indentation• Oliver-Pharr:process causes permanent, plastic deformation
to the sample.

Figure 4 illustrates the powerful capabilities for force curve
analysis available in Oxford Instruments Asylum Research
software. As seen in the figure, the software contains
an exclusive model selection guide to evaluate various
parameters, including plasticity index, force-to-adhesion
ratio, and Tabor coefficient. The selection guide helps

4

Figure 4: Example of force curve modeling with Asylum Research
software. The top window shows a force curve acquired on a silicone
elastomer gel. The applied force versus sample indentation is shownfor both the extend (red) and retract (blue) segments of the cantileverloading-unloading cycle. The bottom window shows the extensive
features of analysis software on all Asylum AFMs. As suggested by the
Model Selection Guide (center of panel), a JKR fit was applied. The
resulting fitted values are displayed in the bottom right of the analysis
panel and are used to generate the black dotted line on the force curve.

users determine the most appropriate mechanical model for
their data. For example, if tip-sample adhesion is present,
the software will alert the user that the Hertz model is not
appropriate. The calculated selection parameters are always
displayed to allow informed decisions.

AFM

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Asylum Research

Bimodal Dual AC™ Imaging
It has been determined that higher-order cantilever modes
provide enhanced sensitivity to material composition. This
discovery resulted in the development of bimodal AFM,
in which two resonant frequencies of the cantilever are
excited simultaneously.12,13 In bimodal AFM, the first, or
lower mode, operates the same as regular tapping mode.
The amplitude of the cantilever is used as the feedback
error signal to obtain topography, and the phase provides
material contrast. In Bimodal Dual AC, a techniquepatented by Asylum Research, a second, higher-order
cantilever resonance is driven simultaneously with thefirst mode; its amplitude and phase response are alsomeasured. As shown in Figure 5, bimodal amplitude andphase images can provide enhanced contrast and spatial
detail relative to conventional phase imaging. However, aswith phase imaging, the contrast in bimodal images can bedifficult to interpret, although, as qualitative data channels,
they can be very useful.

Figure 6: Image of loss tangent tan δ for a commercial coffee
packaging bag in cross-section. Sample features including vapor
barriers, “tie” layers, and a metal layer are clearly distinguished.
Scan size 15 μm. Imaged with the Cypher S AFM.

cases where topography or phase cannot. Due to attractive
forces and dissipative processes, such as adhesion andplasticity, AFM measurements are an upper bound on thematerial’s actual loss tangent. Nonetheless, loss tangent
imaging provides useful estimates with which to assess
viscoelastic materials, as seen in Figure 6.

AM-FM Viscoelastic Mapping Mode

Figure 5: Bimodal Dual AC images of (left) mode 1 phase and (right)
mode 2 phase for a tire sample. The sample contained a blend ofseveral rubbers as well as carbon black and silica. The higher-mode
image shows increased contrast and finer detail. Scan size 500 nm;
data scale in both images is 43°. Imaged with the Cypher S AFM.

Loss Tangent Imaging
Recently, the concept of loss tangent has been applied tophase contrast.14 The loss tangent tan δ = E″/E′ considers
elastic energy and viscous dissipation jointly insteadof treating them independently. It is measured in AFM
experiments from the ratio of dissipated energy to stored
energy per cycle of the tip’s periodic deformation. These
quantities are determined from the amplitude and phase
response in standard tapping mode and are independentof tip-sample contact area in the linear viscoelastic limit.15
As a ratio, the loss tangent alone does not distinguishwhether contrast is due to storage or loss modulus
variations. It can often differentiate sample components in

In addition to loss tangent imaging, further progresshas been made toward quantitative interpretation ofbimodal amplitude and phase measurements in termsof the sample’s nanomechanical properties. Exlusive toOxford Instruments Asylum Research, AM-FM Viscoelastic
Mapping Mode was developed employing bimodal
AFM principles for quantitative mapping of viscoelastic
properties. Its range of applicability spans a remarkable
six orders of magnitude in storage modulus (fromhundreds of kPa to over 100 GPa), making it a highly
versatile technique. Information from AM-FM Mode
includes storage modulus, contact stiffness, loss tangent,and loss modulus.16 A material’s viscoelastic response
provides valuable information in many applications, since
it can strongly influence practical considerations, such as
impact resistance and toughness.
Like Bimodal Dual AC Imaging, AM-FM Mode uses
tapping mode operating simultaneously at two different
cantilever mode frequencies. The lower mode operates
with amplitude modulation (AM) feedback and measurescantilever amplitude and phase. The amplitude yields
a topography image, while the amplitude and phase
together determine the loss tangent, as describedabove. However, in AM-FM Mode, the higher mode
operates with frequency modulation (FM) feedback and

5The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Asylum AFMs for Dynamic
Nanomechanical Modesor phase and loss tangent imaging, GetStarted™
• Fsoftware
automatically sets tapping mode parametersand minimizes setup time on MFP-3D Infinity AFMs.
performed on Cypher family AFMs with small• Whencantilevers, AM-FM Mode provides quantitative
nanomechanical property mapping at much higher
speeds than any other technique.

Figure 7: Elastic modulus overlaid on topography of a tin/leadalloy solder. Tin-rich (lighter) and lead-rich (darker) regions canbe identified. Scan size 8 μm. Acquired in AM-FM Mode on
the Cypher S AFM at 1.5 Hz line scan rate with blueDrive™
photothermal excitation.

measures cantilever frequency and amplitude. Frequency
is a sensitive probe of sample stiffness or elasticity, sothat raw frequency images are a quick way to obtain
qualitative contrast. Quantitative results are obtainedwith a model for tip-sample contact and calibration
measurements on a sample of known modulus. Because
the amplitude of the higher mode is always much lower
than for the lower mode, it does not interfere withfeedback and scanning.
Because AM-FM Mode works like tapping mode, it
has all the advantages of tapping mode, including fastscanning, high spatial resolution, and gentle forces. Asa scanning technique, it is much faster than methods
based on individual force curves and doesn’t deform
samples as much as force curves or contact methods,
such as contact resonance and force modulation imaging(see below). An example of AM-FM Mode on a metallic
solder sample is shown in Figure 7.

Contact Resonance Viscoelastic Mapping
Contact resonance is another dynamic mode that enableshigh resolution, quantitative imaging of both elastic storage
modulus and viscous loss modulus.17,18 It is particularly
well suited to materials with moderate to high modulus(approximately 1-200 GPa). In this mode, a cantilevervibrational resonance is excited while the tip is in contact
with the sample. Quantitative property data is derived
from measurements of the frequency and quality factorof the contact resonance peak. The peak frequency varies
monotonically with the sample’s elastic stiffness, while
the quality factor of the peak changes depending on thesample’s viscous damping.

6

Asylum’s exclusive Bimodal Dual AC™ Mode,• Withsoftware controls enable simultaneous excitation at
two frequencies with independent drive amplitudes.
The detected photodiode signal is processed
simultaneously by two lock-in amplifiers to measure
the phase and amplitude at both frequencies.
ual AC™ Resonance Tracking (DART) and Band• DExcitation(BE) are proprietary Asylum techniques forimaging in Contact Resonance Mode. DART captures
both resonance frequency and quality factor while
operating at normal imaging rates, or even at fastscanning rates with small cantilevers on the Cypher
AFM. BE records the full resonance spectrum, making
it a complementary technique to confirm DART results
or to apply more complex analysis models.
exclusive ModeMaster™ software feature• Asylum’s
makes working with dynamic modes faster and easier.
It automatically configures the software and guides
you through the experiment. For techniques like
AM-FM Mode and Contact Resonance Mode,
the software panel assists in both setting up themeasurement and performing calibrations with areference sample of known modulus. This lets you
start making measurements with well-establishedmethods, but without the full complexity.
spring constants are calibrated easily• Cantilever
and accurately with GetReal software, free on all
Asylum AFMs. Spring constant values are needed, forexample, to measure absolute contact stiffness with
AM-FM Mode and absolute applied force in Contact
Resonance Mode.

Quantitative nanomechanical imaging with contact
resonance requires detecting the resonance peak while thetip scans in contact mode. Although simple in concept, thiscan be challenging in practice because the peak changes
continuously with sample mechanical properties. A variety

AFM

The NanomechPro™ Toolkit: Nanomechanical
AFM Techniques for Diverse Materials

Asylum Researchof hardware and software approaches have been implemented
to meet this challenge. Figure 8 shows an example of Contact
Resonance Mode imaging on a patterned thin film on silicon.
Like other techniques mentioned here, Contact Resonance
Mode can be operated with either minimal calibration for fast,qualitative imaging or can be calibrated with a material of
known properties for more quantitative results. Both Contact
Resonance Viscoelastic Mapping Mode and AM-FM Viscoelastic
Mapping Mode provide quantitative data on viscoelastic
properties, so it can be valuable to compare results directly.
Contact resonance techniques can also be performed much
faster than force curve mapping and are more sensitive onvery stiff materials.

Figure 8: Elastic modulus map overlaid on topography for a patternedtitanium film on silicon. Acquired in DART Contact Resonance Modewith blueDrive™ photothermal excitation on the Cypher AFM. Scan
size 25 µm. Note the ability of Contact Resonance Mode to provide
strong contrast between two materials with very high modulus.

Force Modulation Imaging
Force modulation was one of the earliest AFM techniquesdeveloped for qualitative imaging of nanomechanicalproperties.19,20 It is particularly well suited to relatively
compliant samples (modulus less than about 1 GPa) suchas polymers and biomaterials. Like contact resonance, force
modulation is performed with the tip in contact mode while avery low amplitude, vertical modulation is applied. However, inforce modulation the drive frequency is intentionally far away
from, and usually much lower than, the cantilever contact
resonance. Force modulation uses the idea that a compliant
sample deforms more than a stiff sample for the same force
applied by the tip. Differences in sample deformation, andtherefore contrast in elasticity, are reflected in the relative
amplitude of the cantilever deflection during scanning.
Differences in viscous damping or dissipation are indicatedby the phase lag of the cantilever deflection relative to theexcitation source. Figure 9 contains an example of force
modulation imaging on a multilayer polymer sample.
Models have been developed to interpret force modulation
data in terms of storage modulus and loss tangent, but
quantitative measurements have traditionally been hampered
by non-optimal excitation sources. However, Asylum Research
provides actuators with much flatter frequency response andhigher bandwidth than previously available (see sidebar),offering exciting new possibilities for force modulation. The
actuators make force modulation measurements possible overa wide range of frequencies with high amplitudes. This will
not only provide increased and often different mechanicalcontrast in many applications but will also enable accurate
measurements of frequency-dependent mechanical properties.

Summary

Figure 9: Force modulation amplitude overlaid on topography for apolymer sandwich. The sample contained layers of (left to right) Viton
fluoroelastomer, epoxy, and ethylene propylene diene monomer rubber(EPDM). The difference in hardness between Viton® (Shore A 78) and
EPDM (Shore A 58) is clearly resolved.

Knowledge of nanoscale mechanical properties can be criticalto understanding a material’s behavior and performance. The
diversity of advanced material systems means that no single
AFM technique can provide accurate, detailed informationfor every need. The NanomechPro Toolkit contains a variety
of techniques so that you can choose the best approach for agiven application, on virtually any material. This allows you tomeasure a wide range of properties, including elastic stiffness,
loss and storage modulus, viscous damping, adhesion, andhardness. Different modes, including several available only
on Cypher and MFP-3D family AFMs, probe different types ofmechanical response to provide complementary information.
Contact Asylum Research to explore how techniques in the
NanomechPro Toolkit can benefit your research.

7

Oxford Instruments Asylum Research
AFM Actuators
Dynamic modes, including AM-FM Viscoelastic Mapping
Mode and Contact Resonance Viscoelastic MappingMode, place demands on the excitation source thatare more stringent than standard tapping mode. For
instance, they may require very high bandwidth or very
uniform frequency response; because of this, several
alternatives to the cantilever holder’s piezoelectric
actuator are available to meet these needs.
For contact resonance AFM and high-frequency force
modulation, proprietary sample actuators deliver thebest performance commercially available. They arehighly damped so that small deviations from an ideal,
frequency-independent drive are unlikely to interferewith quantitative measurements. A frequency response
up to ~10 MHz means they are especially valuable forcontact resonance experiments.
For AM-FM Mode and Bimodal Dual AC Imaging,where the tip only contacts the sample a fraction of
the time, sample actuation is not suitable. In addition,
it is not always possible to actuate the sample inContact Resonance Mode or frequency modulation,for instance with a large or oddly-shaped sample orwhen a heating stage is used. For cases like these,
Asylum offers AM-FM Probe holders. Based on thesame technology as sample actuators, they provide
output signals over a wide frequency range withrelatively flat response.
Another approach for all dynamic modes is to actuate
the cantilever directly. blueDrive™ (see figure 8) offersa photothermal laser excitation option for Cypherfamily AFMs and provides exceptionally clean, stable
actuation. Replacing mechanical actuation with thisoption leads to a response that is nearly ideal: flat,
linear, high bandwidth, and operable in air or liquid.

References
1.	H.-J. Butt, B. Cappella, and M. Kappl, Surf. Sci. Rep. 59,
1 (2005).
2.	E. Spedden, D.L. Kaplan, and C. Staii, Phys. Biol. 10,056002 (2013).
3.	C. Braunsmann, R. Proksch, I. Revenko, and T.E. Shäffer,
Polymer 55, 219 (2014).
4.	J. Rother, H. Nöding, I. Mey, and A. Janshoff, Open Biol. 4,
140046 (2014).
5.	G.M. Pharr, W.C. Oliver, and F.R. Brotzen, J. Mater. Res. 7,613 (1992).
6. W.C. Oliver and G.M. Pharr, J. Mater. Res. 19, 3 (2004).
7.	K.R. Gadelrab, M. Chiesa, and F.A. Bonilla, J. Mater. Res.
27, 126 (2012).
8.	K.L. Johnson, Contact Mechanics (Cambridge University
Press, Cambridge, UK, 1985).
9.	D.A. Chernoff, in Proceedings of Microscopy andMicroanalysis, eds. G.W. Bailey et al. (Jones and Begell,
New York, 1995), pp. 888-889.
10.	S.N. Magonov, V. Elings, and M.H. Whangbo, Surface
Science 375, L385 (1997).
11.	J. Tamayo and R. Garcia, Appl. Phys. Lett. 71, 2394 (1997).
12.	T.R. Rodriguez and R. Garcia, Appl. Phys. Lett. 84, 449(2004).
13. R. Proksch, Appl. Phys. Lett. 89, 113121 (2006).
14.	R. Proksch and D.G. Yablon, Appl. Phys. Lett. 100, 073106(2012).
15.	R. Lakes, Viscoelastic Materials (Cambridge University
Press, Cambridge, UK, 2009).
16. R. Garcia and R. Proksch, Eur. Polym. J. 49, 1897 (2013).
17. U. Rabe and W. Arnold, Appl. Phys. Lett. 64, 1493 (1994).
18.	J.P. Killgore, D.G. Yablon, A.H. Tsou, A. Gannepalli, P.A.
Yuya, J.A. Turner, R. Proksch, and D.C. Hurley, Langmuir
27, 13983 (2011).
19.	P. Maivald, H.J. Butt, S.A.C. Gould, C.B. Prater, B. Drake,
J.A. Gurley, V.B. Elings, and P.K. Hansma, Nanotechnology
2, 103 (1991).
20.	M. Radmacher, R.W. Tillmann, and H.E. Gaub, Biophys. J.
64, 735 (1993).

Visit www.Oxford-Instruments.com/AFM to learn more
The foregoing application note is copyrighted by Oxford Instruments Asylum Research, Inc. Oxford Instruments Asylum Research, Inc.
does not intend the application note or any part thereof to form part of any order or contract or regarded as a representation relating
to the products or service concerned, but it may, with acknowledgement to Oxford Instruments Asylum Research, Inc., be used, appliedor reproduced for any purpose. Oxford Instruments Asylum Research, Inc. reserves the right to alter, without notice the specification,
design or conditions of supply of any product or service. Data sheet 43 – 4/2015.

6310 Hollister Avenue
Santa Barbara, CA 93117
Voice+1 (805) 696-6466
Toll free +1 (888) 472-2795
Fax+1 (805) 696-6444

www.oxford-instruments.com/AFM
info@AsylumResearch.com
sales@AsylumResearch.com

FSC® C020739