scholarly journals Data-Driven GENERIC Modeling of Poroviscoelastic Materials

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1165 ◽  
Author(s):  
Chady Ghnatios ◽  
Iciar Alfaro ◽  
David González ◽  
Francisco Chinesta ◽  
Elias Cueto
Keyword(s):  
Indentation Depth ◽  
Soft Materials ◽  
Data Fitting ◽  
Material Behavior ◽  
Data Driven ◽  
High Fidelity ◽  
Force Microscopy ◽  
Atomic Force ◽  
Generic Modeling ◽  
Generic Analysis

Biphasic soft materials are challenging to model by nature. Ongoing efforts are targeting their effective modeling and simulation. This work uses experimental atomic force nanoindentation of thick hydrogels to identify the indentation forces are a function of the indentation depth. Later on, the atomic force microscopy results are used in a GENERIC general equation for non-equilibrium reversible–irreversible coupling (GENERIC) formalism to identify the best model conserving basic thermodynamic laws. The data-driven GENERIC analysis identifies the material behavior with high fidelity for both data fitting and prediction.

scholarly journals Loss of PRCD alters number and packaging density of rhodopsin in rod photoreceptor disc membranes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Emily R. Sechrest ◽  
Joseph Murphy ◽  
Subhadip Senapati ◽  
Andrew F. X. Goldberg ◽  
Paul S.-H. Park ◽  
...  
Keyword(s):  
High Fidelity ◽  
Rod Photoreceptor ◽  
Photoreceptor Degeneration ◽  
Wild Type ◽  
Photoreceptor Outer Segment ◽  
Rod Photoreceptors ◽  
Force Microscopy ◽  
Atomic Force ◽  
Photoreceptor Neurons ◽  
Precise Role

Abstract Progressive rod-cone degeneration (PRCD) is a small protein localized to photoreceptor outer segment (OS) disc membranes. Several mutations in PRCD are linked to retinitis pigmentosa (RP) in canines and humans, and while recent studies have established that PRCD is required for high fidelity disc morphogenesis, its precise role in this process remains a mystery. To better understand the part which PRCD plays in disease progression as well as its contribution to photoreceptor OS disc morphogenesis, we generated a Prcd-KO animal model using CRISPR/Cas9. Loss of PRCD from the retina results in reduced visual function accompanied by slow rod photoreceptor degeneration. We observed a significant decrease in rhodopsin levels in Prcd-KO retina prior to photoreceptor degeneration. Furthermore, ultrastructural analysis demonstrates that rod photoreceptors lacking PRCD display disoriented and dysmorphic OS disc membranes. Strikingly, atomic force microscopy reveals that many disc membranes in Prcd-KO rod photoreceptor neurons are irregular, containing fewer rhodopsin molecules and decreased rhodopsin packing density compared to wild-type discs. This study strongly suggests an important role for PRCD in regulation of rhodopsin incorporation and packaging density into disc membranes, a process which, when dysregulated, likely gives rise to the visual defects observed in patients with PRCD-associated RP.

Direct Writing on Phosphate Glass Using Atomic Force Microscopy for Rapid Fabrication of Nanostructures

2016 ◽  
Author(s):  
Shama F. Barna ◽  
Kyle E. Jacobs ◽  
Glennys A. Mensing ◽  
Placid M. Ferreira
Keyword(s):  
Atomic Force Microscopy ◽  
Ion Beam ◽  
Soft Materials ◽  
Constant Current ◽  
Silver Nanostructures ◽  
Direct Writing ◽  
Ambient Conditions ◽  
Commercial Development ◽  
Force Microscopy ◽  
Atomic Force

Rapid and cost effective fabrication of nanostructures is critical for experimental exploration and translation of results for commercial development. While conventional techniques such as E-beam or Focused Ion beam lithography serve some prototyping needs for nano-scale experimentations, cost and rate considerations prohibit use for manufacturing. Specialized lithographic processes [e.g. nanosphere lithography or interference lithography] are also powerful tools in creating nanostructures but provide limited shapes, positioning and size control of nanostructures. In this work, we demonstrated a liquid-free and mask-less electrochemical writing approach using atomic force microscopy (AFM) that is capable of making arbitrary shapes of silver nanostructures in seconds on a solid state super-ionic (AgI)x (AgPO3)(1−x) glass. Under ambient conditions. silver is extracted selectively on super-ionic (AgI)x (AgPO3)(1−x) glass surface by negatively biasing an AFM probe relative to an Ag film counter electrode. Both voltage controlled and current controlled writings demonstrated localized extraction of silver. The current controlled approach is shown to be the preferred writing approach to make repeatable and uniform patterns of silver on (AgI)x AgPO3(1−x), where x represents the mole fraction of AgI in the mixture and the control parameter that tunes the conductivity of the sample. We demonstrated current controlled printing of silver on two different compositions of the material (i.e. (AgI)0.125 (AgPO3 )0.875 and (AgI)0.25(AgPO3)0.75 ). Depending on the magnitude of the constant current and tip speed, line-width of the silver pattern can be ∼150 nm. The length of these patterns are limited to the maximum distance the tip can be moved using the AFM position controls. The substrate being optically transparent allows the use of this writing technique for rapid prototyping plasmonic devices. By using the patterned substrate as a template for replica molding of soft materials such as polydimethylsiloxane (PDMS), this writing technique can also be utilized for high throughput nano-channel fabrication in biofluidics and microfluidics devices.

Analysis of Indentation: Implications for Measuring Mechanical Properties With Atomic Force Microscopy

1999 ◽  
Vol 121 (5) ◽  
pp. 462-471 ◽  
Author(s):  
K. D. Costa ◽  
F. C. P. Yin
Keyword(s):  
Indentation Depth ◽  
Constitutive Law ◽  
Elastic Materials ◽  
Force Microscopy ◽  
Linear Elastic ◽  
Afm Indentation ◽  
Atomic Force ◽  
Afm Probe ◽  
Nonlinear Elastic ◽  
Indenter Geometry

Indentation using the atomic force microscope (AFM) has potential to measure detailed micromechanical properties of soft biological samples. However, interpretation of the results is complicated by the tapered shape of the AFM probe tip, and its small size relative to the depth of indentation. Finite element models (FEMs) were used to examine effects of indentation depth, tip geometry, and material nonlinearity and heterogeneity on the finite indentation response. Widely applied infinitesimal strain models agreed with FEM results for linear elastic materials, but yielded substantial errors in the estimated properties for nonlinear elastic materials. By accounting for the indenter geometry to compute an apparent elastic modulus as a function of indentation depth, nonlinearity and heterogeneity of material properties may be identified. Furthermore, combined finite indentation and biaxial stretch may reveal the specific functional form of the constitutive law—a requirement for quantitative estimates of material constants to be extracted from AFM indentation data.

scholarly journals Stiffness and heterogeneity of the pulmonary endothelial glycocalyx measured by atomic force microscopy

2011 ◽  
Vol 301 (3) ◽  
pp. L353-L360 ◽  
Author(s):  
Ryan O'Callaghan ◽  
Kathleen M. Job ◽  
Randal O. Dull ◽  
Vladimir Hlady
Keyword(s):  
Atomic Force Microscopy ◽  
Elastic Modulus ◽  
Indentation Depth ◽  
Cell Junctions ◽  
Endothelial Glycocalyx ◽  
Cell Junction ◽  
Microvascular Endothelial Cell ◽  
Cell Contact ◽  
Force Microscopy ◽  
Atomic Force

The mechanical properties of endothelial glycocalyx were studied using atomic force microscopy with a silica bead (diameter ∼18 μm) serving as an indenter. Even at indentations of several hundred nanometers, the bead exerted very low compressive pressures on the bovine lung microvascular endothelial cell (BLMVEC) glycocalyx and allowed for an averaging of stiffness in the bead-cell contact area. The elastic modulus of BLMVEC glycocalyx was determined as a pointwise function of the indentation depth before and after enzymatic degradation of specific glycocalyx components. The modulus-indentation depth profiles showed the cells becoming progressively stiffer with increased indentation. Three different enzymes were used: heparinases III and I and hyaluronidase. The main effects of heparinase III and hyaluronidase enzymes were that the elastic modulus in the cell junction regions increased more rapidly with the indentation than in BLMVEC controls, and that the effective thickness of glycocalyx was reduced. Cytochalasin D abolished the modulus increase with the indentation. The confocal profiling of heparan sulfate and hyaluronan with atomic force microscopy indentation data demonstrated marked heterogeneity of the glycocalyx composition between cell junctions and nuclear regions.

scholarly journals A New Method for Obtaining Model-Free Viscoelastic Material Properties from Atomic Force Microscopy Experiments Using Discrete Integral Transform Techniques

2021 ◽  
Author(s):  
Berkin Uluutku ◽  
Enrique A López-Guerra ◽  
Santiago D Solares
Keyword(s):  
Atomic Force Microscopy ◽  
Integral Transform ◽  
Material Behavior ◽  
New Method ◽  
General Strategy ◽  
Force Microscopy ◽  
Viscoelastic Models ◽  
Model Free ◽  
Atomic Force ◽  
Z Domain

Viscoelastic characterization of materials at the micro- and nanoscales is commonly performed with the aid of force-distance relationships acquired using atomic force microscopy (AFM). The general strategy for existing methods is to fit the observed material behavior to specific viscoelastic models, such as generalized viscoelastic models or power-law rheology models, among others.  Here we propose a new method to invert and obtain the viscoelastic properties of a material through the use of the Z-transform, without using a model.  We present the rheological viscoelastic relations in their classical derivation and their Z-domain correspondence.  We illustrate the proposed technique on a model experiment involving a traditional ramp-shaped force-distance AFM curve, demonstrating good agreement between the viscoelastic characteristics extracted from the simulated experiment and the theoretical expectations. We also provide a path for calculating standard viscoelastic responses from the extracted material characteristics.  The new technique based on the Z-transform is complementary to previous model-based viscoelastic analyses and can be advantageous with respect to Fourier techniques due to its generality.  Additionally, it can handle the unbounded inputs traditionally used to acquire force-distance relationships in AFM, such as “ramp” functions, in which the cantilever position is displaced linearly with time for a finite period of time.

scholarly journals Atomic force microscopy methodology and AFMech Suite software for nanomechanics on heterogeneous soft materials

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Massimiliano Galluzzi ◽  
Guanlin Tang ◽  
Chandra S. Biswas ◽  
Jinlai Zhao ◽  
Shiguo Chen ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Soft Materials ◽  
Force Microscopy ◽  
Atomic Force

Multiparametric characterization of heterogeneous soft materials using contact point detection-based atomic force microscopy

2020 ◽  
Vol 522 ◽  
pp. 146423 ◽  
Author(s):  
Chih-Wen Yang ◽  
Ching-Hsiu Chen ◽  
Ren-Feng Ding ◽  
Hsien-Shun Liao ◽  
Ing-Shouh Hwang
Keyword(s):  
Atomic Force Microscopy ◽  
Contact Point ◽  
Soft Materials ◽  
Force Microscopy ◽  
Atomic Force ◽  
Point Detection ◽  
Multiparametric Characterization
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