Squeeze-out dynamics of nanoconfined water: A detailed nanomechanical study

Khan, Sarfraz; Hoffmann, Peter M.

doi:10.1103/physreve.92.042403

Cited by 13 publications

(26 citation statements)

References 31 publications

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“…We show in this section that a simple minded point-mass model, which suggests that phase and amplitudes are related to the dissipation and stiffness is successful in quantification of viscoelasticity at nano-scale in liquid environment. Many important claims in the past have used point-mass model to quantify stiffness and dissipation of molecular layers from the amplitude and phase (1,3,4,29). The discussion in this section shows that dissipation estimates of liquid layering using point-mass model are accurate.…”

Section: R a F Tmentioning

confidence: 92%

Viscoelasticity of single macromolecules using Atomic Force Microscopy

Patil¹,

Rajput²,

deopa³

et al. 2020

Preprint

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We measured viscoelasticity of single protein molecules using two types of Atomic Force Microscopes (AFM) which employ different detection schemes to measure the cantilever response. We used a commonly available deflection detection scheme in commercial AFMs which measures cantilever bending and a fibre-interferometer based home-built AFM which measures cantilever displacement. For both methods, the dissipation coefficient of a single macromolecule is immeasurably low. The upper bound on the dissipation coefficient is 5 × 10 −7 kg/s whereas the entropic stiffness of single unfolded domains of protein measured using both methods is in the range of 10 mN/m. We show that in a conventional deflection detection measurement, the phase of bending signal can be a primary source of artefacts in the dissipation estimates. It is recognized that the measurement of cantilever displacement, which does not have phase lag due to hydrodynamics of the cantilever, is better suited for ensuring artefact-free measurement of viscoelasticty compared to the measurement of the cantilever bending. We confirmed that the dissipation coefficient in single macromolecules is below the detection limit of AFM by measuring dissipation in water layers confined between the tip and the substrate using similar experimental parameters. Further, we experimentally determined the limits in which the simple point-mass approximation of the cantilever works in off-resonance operation.Single molecules | viscoelasticity | Atomic Force Microscope |

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Section: R a F Tmentioning

confidence: 92%

Viscoelasticity of single macromolecules using Atomic Force Microscopy

Patil¹,

Rajput²,

deopa³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Because both the force, F, and the stiffness, k, are needed to determine the elastic modulus, an AFM technique that can simulateneously measure both parameters is needed. In our case, this is achieved by superimposing a small, sub-molecular dither on the cantilever, and measuring the stiffness [14,15,20,27] and the static deflection/bending of the cantilever, simultaneously.…”

Section: Our Modelmentioning

confidence: 99%

“…The viscoelastic properties of nanoconfined water are particularly important because of its role as the matrix of life and in shaping our planet. When confined, water and other liquids form ordered molecular layers against atomically smooth surfaces [11][12][13][14][15]. This molecular layering gives rise to changes in elastic as well as viscous properties of the confined liquids.…”

mentioning

confidence: 99%

“…This molecular layering gives rise to changes in elastic as well as viscous properties of the confined liquids. While the changes in viscous properties remain highly controversial [13,14,[16][17][18][19][20][21][22][23], the changes in elastic properties (stiffness) of liquids upon confinement are widely observed and established [14,15,19,24,25].…”

mentioning

confidence: 99%

“…For water calculations, we have used previous measurements [15,20] applying an improved analysis of the data.…”

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confidence: 99%

See 2 more Smart Citations

Young’s modulus of nanoconfined liquids?

Khan

Hoffmann

2016

Journal of Colloid and Interface Science

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In material science, bioengineering, and biology, thin liquid films and soft matter membranes play an important role in micro-lubrication, ion transport, and fundamental biological processes. Various attempts have been made to characterize the elastic properties, such as Young's modulus, of such films using Hertz theory by incorporating convoluted mathematical corrections. We propose a simple way to extract tip-size independent elastic properties based on stiffness and force measurement through a spherical tip on a flat surface. Using our model, the Young's modulus of nanoconfined, molecularly-thin, layers of a model liquid TEHOS (tetrakis 2-ethylhexoxy silane) and water were determined using a small-amplitude AFM. This AFM can simultaneously measure the stiffness and forces of nanoscale films. While the stiffness scales linearly with the tip radius, the measured Young's modulus essentially remains constant over an order of magnitude variation in the tip radius. The values obtained for the elastic modulus of TEHOS and water films on the basis of our method are significantly lower than the confining surfaces' elastic moduli, in contrast with the uncorrected Hertz model, suggesting that our method can serve as a simple way to compare elastic properties of nanoscale thin films as well as to characterize a variety of soft films. In addition, our results show that the elastic properties (elastic modulus) of nanoconfined liquid films remain fairly independent of increasing confinement.

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Stationary probability densities of generalized Maxwell-type viscoelastic systems under combined harmonic and Gaussian white noise excitations

Wang

2020

J Braz. Soc. Mech. Sci. Eng.

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Viscoelasticity has been widely studied over the past few decades as a combination of the viscous effects of energy dissipation and the elastic effects of energy storage. As an application, viscoelastic dampers are commonly used to suppress the dynamic behaviour of structures. However, in an actual physical environment, it is difficult to explore the stationary probability densities of random responses for viscoelastic systems. For this purpose, we present a numerical method to investigate the dynamic behaviour of a generalized Maxwell-type viscoelastic system under harmonic and Gaussian white noise excitations. Using approximate equivalent and stochastic averaging, we establish an averaged Itô differential equation for the amplitude of the system. For primary external resonance, we solve the reduced Fokker-Planck-Kolmogorov equation by using the successive over-relaxation technique combined with a finite difference method. Through Monte Carlo simulations, we verify the applicability, accuracy and efficiency of the proposed methodology and demonstrate that viscoelasticity has a significant impact on the dynamic behaviour of the viscoelastic systems. This work reveals the remarkable influences of viscoelasticity, excitation intensities, linear and nonlinear damping and linear and nonlinear stiffness on the probability density functions of system responses, which can guide the selection of materials, stiffnesses and structures in viscoelastic damper design.

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Squeeze-out dynamics of nanoconfined water: A detailed nanomechanical study

Cited by 13 publications

References 31 publications

Viscoelasticity of single macromolecules using Atomic Force Microscopy

Viscoelasticity of single macromolecules using Atomic Force Microscopy

Young’s modulus of nanoconfined liquids?

Stationary probability densities of generalized Maxwell-type viscoelastic systems under combined harmonic and Gaussian white noise excitations

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