Nanomechanical Properties

Because AFM is based on forces between the nanoprobe tip and the surface, the method is inherently suited to analyze mechanical properties of polymers. This has been realized experimentally very early [35]. For polymers, the determination of nanomechanical response of polymers, measurements of viscoelasticity by contact resonance force microscopy [36] and AFM nanorheology [37] have been reported. These more specialized modes are not further discussed as they are not considered to be standard methods. 

Elastic properties can be assessed quantitatively by AFM in point-by-point force-displacement measurements (nanoindentation). The rigorous quantification of elastic moduli requires a thorough characterization of the indenter geometry and size as well as the use of an appropriate model to describe the contact between tip and sample. Previous work, for example, by Tranchida et al. [38] and Cappella and coworkers [39] has shown that excellent agreement between data from conventional mechanical testing and AFM nanoindentation can be obtained (see also Chapter 17). 

IMAGING POLYMER MORPHOLOGY USING ATOMIC FORCE MICROSCOPY 

Fischinger et al. [42]. Reproduced with permission of American Chemical Society. 

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Burnham N A and Colton R J 1989 Measuring the nanomechanical properties and surface forces of materials using atomic force microscope J. Vac. Sc/. Technol. A 7 2906... 

Mingwu, Bai, Koji, Kato, Noritsugu, Umehara, Yoshihiko, Miyake, Xu, Junguo, and Hiromitsu, Tokisue, "Dependence of Microstructure and Nanomechanical Properties of Amorphous Carbon Nitride Thin Films on Vacuum Annealing, Thin SoZ/dFz Zms, Vol. 376,2000, pp. 170-178. 

Carpick RW, Sasaki DY, Marcus MS, Eriksson MA, Bums AR. Polydiacetylene films a review of recent investigations into chromogenic transitions and nanomechanical properties. J Phys Condens Matter 2004 16 R679-R697. 

Marshall GW, Habelitz S, Gallagher R, Balooch M, Balooch G, Marshall SJ Nanomechanical properties of hydrated carious human dentin. J Dent Res 2001 80 1768-1771. 

Nanomechanical properties show a distinct dependence on the deposition temperature. Films deposited at 20-200°C possess the highest hardness up to 14 GPa. The lowest friction coefficient was measured for films deposited at 400-600°C. Generally, the CNX-Ni films have higher hardness and elastic modulus but lower coefficient of friction than their C-Ni counterpart films probably due to nitrogen cross-links between graphitic layers. 

N.A. Burnham and R.J. Colton. Measuring the Nanomechanical Properties and Surface Forces of Materials Using an Atomic Force Microscope. J. Vacuum Sci. Technol. A 7 2906 (1989). 

These observations suggest an interaction between DDA and MW effects on chitosan nanomechanical properties but the study was not able to clearly separate out the effects [90]. Additional studies are needed to better delineate the role of these factors on nanomechanical properties and their importance to interactions between chitosan coatings and host cells or tissues. 

Majd S et al (2009) Effects of material property and heat treatment on nanomechanical properties of chitosan Aims. J Biomed Mater Res B Appl Biomater 90(l) 283-289... 

Lemieux M, Usov D, Minko S, Stamm M, Shulha H, Tsukruk W. Reorganization of binary polymer brushes reversible switching of surface microstructures and nanomechanical properties. Macromolecules 2003 36(19) 7244—55. 

We have discussed the recent progress in nanomechanical property evaluation using AFM based on JKR analysis. Sufficiently elastic materials such as PDMS 10 can be treated within the JKR framework, whereas viscoelastic character causes a large deviation from JKR theory, as observed in the case of PDMS3 or UR. 

Paparcone R, Keten S, Buehler MJ (2010) Atomistic simulation of nanomechanical properties of Alzheimer s Ap(l-40) amyloid fibrils under compressive and tensile loading. J Biomech 43... 

Cerf, A., Cau, J. C., Vieu, C., and Dague, E. 2009. Nanomechanical properties of dead or alive single-patterned bacteria, Langmuir 25,5731-5736. 

Tyagi, P., Catledge, S.A., Stanishevsky, A., Thomas, V., Vohra, Y.K. Nanomechanical properties of electrospun composite scaffolds based on polycaprolactone and hydroxyapatite. J. Nanosci. Nanotechnol. 9,4839-4845 (2009)... 

Yaghoubi, H., Taghavinia, N., and Alamdari, E.K. (2010) Self cleaning Ti02 coating on polycarbonate surface treatment, photocatalytic and nanomechanical properties. Suif. Coat. Technol,... 

Kluge D, Abraham F, Schmidt S, Schmidt FI-W, Feiy A. Nanomechanical Properties of Supramolecular Self-Assembled Whiskers Determined by AFM Force Mapping. Langmuir. 2010 26(5) 3020-3. 

Nanoindentation tests were used by Dhaka and collaborators to study the effect of various organoclay concentrations on the nanomechanical properties of UP nanocomposites [10]. A strong correlation was found between the mechanical properties and interlayer d-spacing of clay particles in the nanocomposite system. Cured UP resins with incorporated 1%, 3%, and 5 wt% organoclay exhibited hardness increased by 29%, 24%, and 14%, respectively. Also the elastic modulus was increased by 23% with the introduction of 5 wt% organoclay. 

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