Depth sensing-induced inelastic deformation at heterogeneous polymer surface

Lian, Dai; Sorkin, V.; Zhang, Yong‐Wei

doi:10.1016/j.polymer.2015.05.002

Cited by 2 publications

(5 citation statements)

References 39 publications

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“…Via atomic shufflings, F atoms were in closest proximity to the tip surface, while C atoms and O atoms remained farther away from the tip. These observations are consistent with those of a previous study [20]. Besides, atoms of the segment moved slightly forward along the -x-axis, due to the push and drag from the sliding tip.…”

Section: Sds Regimesupporting

confidence: 93%

“…Therefore, when the tip is approaching, the C atoms in the lube are the first to experience a transition from attraction to repulsion, followed by the O atoms, and then the F atoms. It is noted that since the H atom has a very low molar concentration in the ZDOL film (4%), its contribution to the total VDW force is negligible [20].…”

Section: Methodsmentioning

confidence: 99%

“…For heterogeneous polymers, such as ZDOL, it has been shown that upon contacting with ta-C surfaces, intrinsic shufflings occur due to the different characteristics of van der Waals (VDW) interactions within different atomic species [20]. However, in depth-sensing using atomic force microscopy, the probing tip is not only contacting the polymer surface, but also sliding on it.…”

Section: Introductionmentioning

confidence: 99%

“…In earlier works, the applied normal force was large (normally beyond the level of nanonewtons [22]), and the tip was able to cause severe and permanent structural alternation to the polymer. Nowadays, the probing force for surface depth-sensing has been reduced to the level of nanonewtons, or even lower [20]. At such a low force scale, the sensing tip is can probe only a small number of discrete atoms across the interface at a time [23].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Probing the surface profile and friction behavior of heterogeneous polymers: a molecular dynamics study

Lian¹,

Sorkin²,

Zhang³

2017

Modelling Simul. Mater. Sci. Eng.

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We perform molecular dynamics simulations to investigate molecular structure alternation and friction behavior of heterogeneous polymer (perfluoropolyether) surfaces using a nanoscale probing tip (tetrahedral amorphous carbon). It is found that depending on the magnitude of the applied normal force, three regimes exist: the shallow depth-sensing (SDS), deep depth-sensing (DDS), and transitional depth-sensing (TDS) regimes; TDS is between SDS and DDS. In SDS, the tip is floating on the polymer surface and there is insignificant permanent alternation in the polymer structure due to largely recoverable atomic deformations, and the surface roughness profile can be accurately measured. In DDS, the tip is plowing through the polymer surface and there is significant permanent alternation in the molecular structure. In this regime, the lateral friction force rises sharply and fluctuates violently when overcoming surface pile-ups. In SDS, the friction can be described by a modified Amonton’s law including the adhesion effect; meanwhile, in DDS, the adhesion effect is negligible but the friction coefficient is significantly higher. The underlying reason for the difference in these regimes rests upon different contributions by the repulsion and attraction forces between the tip and polymer surfaces to the friction force. Our findings here reveal important insights into lateral depth-sensing on heterogeneous polymer surfaces and may help improve the precision of depth-sensing devices.

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Section: Sds Regimesupporting

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Probing the surface profile and friction behavior of heterogeneous polymers: a molecular dynamics study

Lian¹,

Sorkin²,

Zhang³

2017

Modelling Simul. Mater. Sci. Eng.

View full text Add to dashboard Cite

show abstract

“…To predict the length scale effects mentioned above, atomistic simulations may be tempting, as length scale effects have been found to be dependent on polymer molecular structure [7,15]. While molecular simulations may provide some basis for general trends [34,35], they have their limitations as (i) deformation in polymers is highly dissipative and require large time scales, so that extreme computation times are necessary merely to determine atomistic positions prior to any load induced deformation and (ii) these effects occur at length scales of more than 1 μm. Therefore, atomistic simulations that can be quantitatively compared with experiments are arguably unrealistic for time being.…”

Section: Non-local Rotation Gradient Theorymentioning

confidence: 99%

Length scale dependence in elastomers – comparison of indentation experiments with numerical simulations

Garg

Han

Alisafaei

2016

Polymer

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Probing depth dependent deformation at nano-and micrometer length scales has been observed in indentation experiments of polymers. Unlike in metals, where size effects are observed in plastic deformation and are attributed to geometrically necessary dislocations, the origin of size dependence in polymers is not well understood. As classical continuum theories are unable to describe such phenomena, higher order gradient theories have been developed to capture such size dependent deformation behavior. The present study adopts the penalty finite element approach for a couple stress elasticity theory under axisymmetric conditions to numerically simulate and analyze the probing depth dependent deformation. Polydimethylsiloxane (PDMS) and natural rubber have been used as model materials to analyze the depth dependent deformation at different probing depths. Simulations were performed on PDMS using spherical indenter tips of different radii to show the influence of strain/rotation gradients on elastic modulus. To capture the experimentally observed increase in hardness with decreasing probing depth, simulations applying a conical indenter tip were performed and compared with experimental data.

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Depth sensing-induced inelastic deformation at heterogeneous polymer surface

Cited by 2 publications

References 39 publications

Probing the surface profile and friction behavior of heterogeneous polymers: a molecular dynamics study

Probing the surface profile and friction behavior of heterogeneous polymers: a molecular dynamics study

Length scale dependence in elastomers – comparison of indentation experiments with numerical simulations

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