Measurement of Pull-Off Forces by Atomic Force Microscope in Liquids Used for Biological Applications

Kwon, Eun Young; Kim, Y.‐T.; Park, Jongho; Kim, D.‐E.; Jung, Haejoon

doi:10.1111/j.1747-1567.2007.00178.x

Cited by 3 publications

(4 citation statements)

References 13 publications

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“…Adhesion forces were observed for only a few samples in force (loading and unloading) versus time profiles in any of the studies (data not shown; for an example profile, see Ladjal et al, 2010). The adhesion detected in these samples could be due to the wear of the spherical probe (Kwon et al, 2007). In those few samples, this force was negligible (less than 0.05 times the maximum indentation force) compared to the adhesion force (more than 0.1 times the maximum indentation force) observed by other researchers (Cao et al, 2005;Girot et al, 2006;Kwon et al, 2007).…”

Section: Analytical Modelingmentioning

confidence: 85%

“…The adhesion detected in these samples could be due to the wear of the spherical probe (Kwon et al, 2007). In those few samples, this force was negligible (less than 0.05 times the maximum indentation force) compared to the adhesion force (more than 0.1 times the maximum indentation force) observed by other researchers (Cao et al, 2005;Girot et al, 2006;Kwon et al, 2007). Hence, the adhesion force was not considered in the subsequent analyses, and the JKR and DMT models were not applicable (Ladjal et al, 2010;Pillarisetti, 2009).…”

Section: Analytical Modelingmentioning

confidence: 89%

See 1 more Smart Citation

Mechanical Phenotyping of Mouse Embryonic Stem Cells: Increase in Stiffness with Differentiation

Pillarisetti

Desai

Ladjal

et al. 2011

Cellular Reprogramming

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Atomic force microscopy (AFM) has emerged as a promising tool to characterize the mechanical properties of biological materials and cells. In our studies, undifferentiated and early differentiating mouse embryonic stem cells (mESCs) were assessed individually using an AFM system to determine if we could detect changes in their mechanical properties by surface probing. Probes with pyramidal and spherical tips were assessed, as were different analytical models for evaluating the data. The combination of AFM probing with a spherical tip and analysis using the Hertz model provided the best fit to the experimental data obtained and thus provided the best approximation of the elastic modulus. Our results showed that after only 6 days of differentiation, individual cell stiffness increased significantly with early differentiating mESCs having an elastic modulus two-to threefold higher than undifferentiated mESCs, regardless of cell line (R1 or D3 mESCs) or treatment. Singletouch (indentation) probing of individual cells is minimally invasive compared to other techniques. Therefore, this method of mechanical phenotyping should prove to be a valuable tool in the development of improved methods of identification and targeted cellular differentiation of embryonic, adult, and induced-pluripotent stem cells for therapeutic and diagnostic purposes.

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Section: Analytical Modelingmentioning

confidence: 85%

Section: Analytical Modelingmentioning

confidence: 89%

Mechanical Phenotyping of Mouse Embryonic Stem Cells: Increase in Stiffness with Differentiation

Pillarisetti

Desai

Ladjal

et al. 2011

Cellular Reprogramming

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“…Here, several comments follow with regards to the measurement accuracy and deviations of the observed data. In general, the pull-off force depends on a variety of conditions such as the radius of the AFM tip, contamination of the tip or the inert liquid, and temperature [33,43,44]. Specifically, the pull-off force is severely affected by the size and geometry of the AFM tip.…”

Section: Comments On the Measurement Accuracy And Deviationsmentioning

confidence: 99%

“…Of these, the use of an inert liquid environment is more convenient and cost effective since conventional AFM allows for an operating mode in air as well as in liquid. In fact, many researchers have used the AFM liquid mode to measure adhesion or hardness of biomaterials [29,30], wear or rheology of liquids [31,32] and pull-off forces [25,33,34]. Therefore, we employ here the liquid-phase mode of AFM using an inert PFD solvent and measure the intermolecular interactions of an AFM tip and an imprinted nanopattern in a non-polar, nonreactive environment.…”

Section: Introductionmentioning

confidence: 99%

Measurement of pull-off force on imprinted nanopatterns in an inert liquid

Kim

Lee

et al. 2010

Nanotechnology

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We report on the measurement of the pull-off force on nanoscale patterns that are formed by thermal nanoimprint lithography (t-NIL). Various patterns with feature sizes in the range of 50-900 nm were fabricated on silicon substrates using a rigiflex polymeric mold of ultraviolet curable polyurethane acrylate (PUA, Young's modulus approximately 1 GPa) or perfluoropolyether (PFPE, Young's modulus approximately 10.5 MPa) and a resist layer of polystyrene (PS) of three different molecular weights (M(w) = 18,100, 211,600 and 2043,000). The pull-off force was measured in non-polar, non-reactive perfluorodecalin (PFD) solvent between a sharp atomic force microscopy (AFM) tip and an imprinted pattern. Our experimental data demonstrated that the measured pull-off forces were in good agreement with a simple adhesion model based on Lifshitz theory. Also, the force on the pressed region (valley) is higher than that on the cavity region (hill), with the ratio (hill/valley) decreasing with the decrease of pattern size and the increase of molecular weight. The confinement effects were more pronounced for smaller patterns (<300 nm) and higher molecular weights (M(w) = 211,600 and 2043,000) presumably due to sluggish movement of polymer chains into nano-cavities. Finally, the experimental observations were compared with molecular dynamic simulations based on a simplified amorphous polyethylene model.

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Atomic force microscopy-based single-cell indentation: Experimentation and finite element simulation

Ladjal

Hanus

Pillarisetti

et al. 2009

2009 IEEE/RSJ International Conference on Intelligent Robots and Systems

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International audienceIn order to understand and characterize the mechanical property and response of the mouse embryonic stem cells (mESC), we used an atomic force microscope (AFM) combined with a PHANToM haptic feedback device. Atomic force microscopy has rapidly become a valuable tool for quantifying the biophysical properties of single cells or a collection of cells through force measurements. We report herein the mechanical characterization of single mESC using indentation-relaxation measurements with micro-sphere AFM probes for fixed and live undifferentiated mESC. During cell indentation for both live and fixed undifferentiated cells, we provided force feedback to the user in real-time through the PHANToM haptic feedback device as the AFM tip was deforming the cell. The force was amplified for the human operator to perceive the change in force during cell indentation by the AFM cantilever. This information can be used as a mechanical marker to characterize state of the cell (live and fixed). As the interpretation of atomic force microscopy-based indentation tests is highly dependent on the use of an appropriate theoretical model of the testing configuration, various contact models are presented to predict the mechanical behavior of an individual mouse embryonic stem cells (mESC) in different states. A comparison study with finite element simulations (FEM) of spherical tip indentation demonstrates the effectiveness of our computational model to predict the mESC deformation during indentation and relaxation nanomanipulation tasks

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Measurement of Pull-Off Forces by Atomic Force Microscope in Liquids Used for Biological Applications

Cited by 3 publications

References 13 publications

Mechanical Phenotyping of Mouse Embryonic Stem Cells: Increase in Stiffness with Differentiation

Mechanical Phenotyping of Mouse Embryonic Stem Cells: Increase in Stiffness with Differentiation

Measurement of pull-off force on imprinted nanopatterns in an inert liquid

Atomic force microscopy-based single-cell indentation: Experimentation and finite element simulation

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