Surface Chemical Analysis

Call for Participation

Technical Work Area 2

Project A38

Inter-laboratory study: elastic modulus
measurement for compliant materials using an
atomic force microscope
Objectives
The aim of this inter-laboratory study
is to compare the elastic modulus ofcompliant materials calculated by thelinearized JKR method1, which wasdeveloped recently, with that by thetwo-point JKR method2 adopted in theprocedure of ISO 21222:2020.

The results of the study will be used
for the future revision of ISO 21222.

Background
AFM
force-distancecurve
measurements are used to determinethe elastic moduli of compliant
materials such as organics andpolymers at surfaces. The moduli arecalculated from the curve fitting of acontact mechanic model to the curves.
It is necessary to select a proper
contact mechanic model and to use anappropriate calculation procedure.

Standardization Needs
The
recently
publishedISO
21222:2020 ‘Procedure for thedetermination of elastic moduli forcompliant materials using atomic force

microscope and the two-point JKR
method’ employs the two-point JKR
method for modulus determination, asits title indicates. This method is verysimple and easy to use but there areseveral limitations. Only two points ofthe curves can be used and thus, thecalculated modulus tends to be affected
more by noise on the curve thanconventional curve fitting which involves
more data points. Another limitation isthat the force region used in fitting isfixed and thus, the repulsive force region
cannot be involved in fitting.
Recently the linearized JKR method wasdeveloped, which is free from theselimitations but still easy to use. It isexpected that introducing the linearized
JKR method improves the applicabilityof the modulus determination. This interlaboratory study aims to validate theadvantages of the linearized JKR
method over the two-point JKR method.

Work Programme
Two kinds of compliant samples having
different elastic moduli will be delivered
together with cantilevers for therespective samples. Participants will be
asked to perform multiple forcedistance curve measurements on the(a) Example force-indentation curve on PDMS and (b) its linearized form calculated during
the linearized JKR method procedure.

provided samples with the providedcantilevers
underatmosphericconditions and to report the elasticmoduli calculated from the method
described in the protocol that will bedelivered later.

Deliverables andDissemination
Results that evaluate the variance ofthe elastic modulus calculated fromthe respective methods will bereported in International Symposium
on SPM Standardization. Results willbe also published in a peer-reviewed
journal and will be used in the futurerevision of ISO 21222.

References
[1]

[2]

Fujinami, S., Ueda, E., Nakajima, K.,
Nishi T., J. Polym. Sci. Part B Polym.
Phys., 57, 1279–1286 (2019).
Sun, Y., Akhremitchev, B., Walker,
G. C., Langmuir, 20, 5837–5845(2004).

For more information on
participation, please contact:

Prof. So Fujinami

Kyoto University, Japan
Email: fujinami.so.8z@kyoto-u.ac.jp

Prof. Ken Nakajima

Project Leader,Tokyo Institute of Technology, Japan
Email: knakaji@mac.titech.ac.jp

Prof. Ian Gilmore
Chair, VAMAS TWA 2

National Physical Laboratory, UK
Email: ian.gilmore@npl.co.uk

www.vamas.org
September 2022