Mapping of Nanoscale Mechanical Properties of Polymers in Quasi-static and Oscillatory Atomic Force Microscopy Modes

MRS Advances ◽  
2016 ◽  
Vol 1 (40) ◽  
pp. 2763-2768 ◽  
Author(s):  
Sergei Magonov ◽  
Marko Surtchev ◽  
John Alexander ◽  
Ivan Malovichko ◽  
Sergey Belikov

ABSTRACTRecent advances in studies of local mechanical properties of polymers with different atomic force microscopy techniques (contact, Hybrid and amplitude modulation modes) are described in interplay between experiment and theory. Analysis of force curves and time dependencies of probe response to sample compliance, which were recorded on a number of polymer materials at various temperatures, leads to quantitative mapping of specific mechanical properties (elastic modulus, work of adhesion, etc). High spatial resolution of elastic modulus mapping (10-20 nm) is illustrated in measurements of lamellar structures of several polymers. Challenges of examination of viscoelastic properties are pointed out and a possible solution is presented.

2019 ◽  
Vol 54 (15) ◽  
pp. 2065-2071 ◽  
Author(s):  
M Subbir Parvej ◽  
Xinnan Wang ◽  
Joseph Fehrenbach ◽  
Chad A Ulven

Kenaf ( Hibiscus cannabinus L.) fiber is being extensively used as a reinforcement material in composites due to its excellent mechanical properties. To use this fiber more efficiently, it is necessary to understand its mechanical properties at micro/nano meter scale. Despite the evidence of some past studies to determine the elastic modulus of kenaf fiber, most of them were performed on fiber bundles. Bundle-based method to find the elastic moduli has some obvious issues of foreign materials being present, incorrect gauge length, and sample diameter due to void spaces. These issues pose as obvious hurdles to determine the elastic modulus accurately. In this study, individual kenaf micro fiber was used to find elastic modulus in the radial direction. The radial elastic modulus of the fiber was characterized by atomic force microscopy-based nanoindentation. To determine the radial elastic modulus from the force versus sample deformation data, the extended Johnson–Kendall–Roberts model was used which considered adhesion force from the fiber surface. The radial elastic modulus of the kenaf fiber was found to be 2.3 GPa.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
J. K. Wenderott ◽  
Carmen G. Flesher ◽  
Nicki A. Baker ◽  
Christopher K. Neeley ◽  
Oliver A. Varban ◽  
...  

AbstractObesity-related type 2 diabetes (DM) is a major public health concern. Adipose tissue metabolic dysfunction, including fibrosis, plays a central role in DM pathogenesis. Obesity is associated with changes in adipose tissue extracellular matrix (ECM), but the impact of these changes on adipose tissue mechanics and their role in metabolic disease is poorly defined. This study utilized atomic force microscopy (AFM) to quantify difference in elasticity between human DM and non-diabetic (NDM) visceral adipose tissue. The mean elastic modulus of DM adipose tissue was twice that of NDM adipose tissue (11.50 kPa vs. 4.48 kPa) to a 95% confidence level, with significant variability in elasticity of DM compared to NDM adipose tissue. Histologic and chemical measures of fibrosis revealed increased hydroxyproline content in DM adipose tissue, but no difference in Sirius Red staining between DM and NDM tissues. These findings support the hypothesis that fibrosis, evidenced by increased elastic modulus, is enhanced in DM adipose tissue, and suggest that measures of tissue mechanics may better resolve disease-specific differences in adipose tissue fibrosis compared with histologic measures. These data demonstrate the power of AFM nanoindentation to probe tissue mechanics, and delineate the impact of metabolic disease on the mechanical properties of adipose tissue.


2018 ◽  
Vol 2 (2) ◽  
pp. 24-29
Author(s):  
Ahmed Kazaili ◽  
Riaz Akhtar

Understanding of the ultrastructure and nanomechanical behavior of the cornea is important for a number of ocular disorders. In this study, atomic force microscopy (AFM) was used to determine nanoscale changes in the porcine cornea following enzymatic degradation. Diff erent concentrations of amylase were used to degrade the cornea. A reduction in elastic modulus at the nanoscale, along with disrupted collagen morphology, was observed following enzymatic treatment. This study highlights the interplay between mechanical properties and collagen organization in the healthy cornea.


2021 ◽  
pp. 1-10
Author(s):  
Ngoc-Phat Huynh ◽  
Tuan-Em Le ◽  
Koo-Hyun Chung

Atomic force microscopy (AFM) can determine mechanical properties, associated with surface topography and structure, of a material at the nanoscale. Force–indentation curves that depict the deformation of a target specimen as a function of an applied force are widely used to determine the elastic modulus of a material based on a contact model. However, a hysteresis may arise due to friction between the AFM tip and a specimen. Consequently, the normal force detected using a photodetector during extension and retraction could be underestimated and overestimated, respectively, and the extension/retraction data could result in a significant difference in the elastic modulus measurement result. In this study, elastic modulus and friction coefficient values were determined based on an in situ theoretical model that compensated for the effect of friction on force–indentation data. It validated the proposed model using three different polymer specimens and colloidal-tipped probes for the force–indentation curve and friction loop measurements. This research could contribute to the accurate measurement of mechanical properties using AFM by enhancing the interpretation of force–indentation curves with friction-induced hysteresis. Furthermore, the proposed approach may be useful for analyzing in situ relationships between mechanical and frictional properties from a fundamental tribological perspective.


1996 ◽  
Vol 440 ◽  
Author(s):  
M. R. Vanlandingham ◽  
S. H. Mcknight ◽  
G. R. Palmese ◽  
R. F. Eduljee ◽  
J. W. Gillespie ◽  
...  

AbstractThe atomic force microscope (AFM) has become a popular tool for characterizing surfaces of many different types of materials. In this paper, an AFM is used to probe the mechanical properties of polymer samples through examination of force curves produced during tip-sample contact and indentation. Three types of cantilever probes with spring constants estimated to be 1–5 N/m, 20–100 N/m, and 400–500 N/m respectively, were used to study different polymer samples with known modulus values ranging from 20 MPa to 3 GPa. A technique is developed that relates the measured sample response to elastic modulus, and illuminates the importance of the relative stiffnesses of the cantilever probe and the sample to the material response.


Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1020 ◽  
Author(s):  
Ji Zhou ◽  
Qiang Cai ◽  
Fu Xu

Polyimide@graphene oxide (PI@GO) composites were prepared by way of a simple solution blending method. The nanoscale hardness and Young’s modulus of the composites were measured using nanoindentation based on atomic force microscopy (AFM). A nanoscale hardness of ~0.65 GPa and an elastic modulus of ~6.5 GPa were reached with a load of ~55 μN. The indentation recovery on the surface of PI@GO was evaluated. The results show that relatively low GO content can remarkably improve the nanoscale mechanical properties of PI.


2019 ◽  
Vol 10 ◽  
pp. 1332-1347 ◽  
Author(s):  
Zahra Abooalizadeh ◽  
Leszek Josef Sudak ◽  
Philip Egberts

Dynamic atomic force microscopy (AFM) was employed to spatially map the elastic modulus of highly oriented pyrolytic graphite (HOPG), specifically by using force modulation microscopy (FMM) and contact resonance (CR) AFM. In both of these techniques, a variation in the amplitude signal was observed when scanning over an uncovered step edge of HOPG. In comparison, no variation in the amplitude signal was observed when scanning over a covered step on the same surface. These observations qualitatively indicate that there is a variation in the elastic modulus over uncovered steps and no variation over covered ones. The quantitative results of the elastic modulus required the use of FMM, while the CR mode better highlighted areas of reduced elastic modulus (although it was difficult to convert the data into a quantifiable modulus). In the FMM measurements, single atomic steps of graphene with uncovered step edges showed a decrease in the elastic modulus of approximately 0.5%, which is compared with no change in the elastic modulus for covered steps. The analysis of the experimental data taken under varying normal loads and with several different tips showed that the elastic modulus determination was unaffected by these parameters.


CrystEngComm ◽  
2019 ◽  
Vol 21 (38) ◽  
pp. 5738-5748 ◽  
Author(s):  
François S. Hallac ◽  
Ioannis S. Fragkopoulos ◽  
Simon D. Connell ◽  
Frans L. Muller

This work describes a new method to measure breakage strength and elastic modulus of single crystal cantilevers using atomic force microscopy.


Soft Matter ◽  
2020 ◽  
Vol 16 (28) ◽  
pp. 6457-6462 ◽  
Author(s):  
Hailong Li ◽  
Katarzyna Mystek ◽  
Lars Wågberg ◽  
Torbjörn Pettersson

We probe the elastic modulus of cellulose gel beads during drying by indentation with atomic force microscopy.


2019 ◽  
Vol 9 (2) ◽  
pp. 3894-3897

This paper proposed an approach for analyzing surface modification of nanoparticles based on atomic force microscopy (AFM). The work was carried out on unmodified gold nanoparticles and gold nanoparticles coated with a protein shell (a conjugate of gold nanoparticles and immunoglobulin G). The proposed analysis of surface modification of gold nanoparticles consists of the registration of force curves, which reflect the dependences of the deflection of the beam of the AFM probe when interacting with the surface from moving the cantilever in the vertical direction. The elastic modulus and the force of the interaction between the probe and the modified or unmodified surface of the nanoparticles are proposed as the parameters characterizing the modification. Significant differences were obtained between the unmodified and modified gold nanoparticles using the AFM method in the spectroscopy mode.


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