scholarly journals Nanomechanical Properties of Engineered Cardiomyocytes Under Electrical Stimulation

2021 ◽  
Author(s):  
Lia Pailino ◽  
Lihua Lou ◽  
Alberto Sesena Rubfiaro ◽  
Jin He ◽  
Arvind Agarwal
Keyword(s):  
Mechanical Properties ◽  
Electrical Stimulation ◽  
Elastic Modulus ◽  
Cardiac Tissue ◽  
Control Mode ◽  
Adult Cardiomyocytes ◽  
Fetal Cardiomyocytes ◽  
Induced Pluripotent ◽  
Fluid Cell

Engineered cardiomyocytes made of human-induced pluripotent stem cells (iPSC) present phenotypical characteristics similar to human fetal cardiomyocytes. There are different factors that are essential for engineered cardiomyocytes to be functional, one of them being that their mechanical properties must mimic those of adult cardiomyocytes. Techniques, such as electrical stimulation, have been used to improve the extracellular matrix's alignment and organization and improve the intracellular environment. Therefore, electrical stimulation could potentially be used to enhance the mechanical properties of engineered cardiac tissue. The goal of this study is to establish the effects of electrical stimulation on the elastic modulus of engineered cardiac tissue. Nanoindentation tests were performed on engineered cardiomyocyte constructs under seven days of electrical stimulation and engineered cardiomyocyte constructs without electrical stimulation. The tests were conducted using BioSoft™ In-Situ Indenter through displacement control mode with a 50 µm conospherical diamond fluid cell probe. The Hertzian fit model was used to analyze the data and obtain the elastic modulus for each construct. This study demonstrated that electrically stimulated cardiomyocytes (6.98 ± 0.04 kPa) present higher elastic modulus than cardiomyocytes without electrical stimulation (4.96 ± 0.29 kPa) at day 7 of maturation. These results confirm that electrical stimulation improves the maturation of cardiomyocytes. Through this study, an efficient nanoindentation method is demonstrated for engineered cardiomyocyte tissues, capable of capturing the nanomechanical differences between electrically stimulated and non-electrically stimulated cardiomyocytes.

Test Methods for Mechanical Properties of Structural Adhesives

2010 ◽  
Vol 97-101 ◽  
pp. 814-817 ◽  
Author(s):  
Jun Deng
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Shear Strength ◽  
Elastic Modulus ◽  
Butt Joint ◽  
Test Methods ◽  
Joint Specimen ◽  
Lap Shear ◽  
Better Than

One of the greatest drawbacks to predicting the behaviour of bonded joints has been the lack of reliable data on the mechanical properties of adhesives. In this study, methods for determining mechanical properties of structural adhesive were discussed. The Young’s modulus, Poisson’s ratio and tensile strength of the adhesive were tested by dogbone specimens (bulk form) and butt joint specimens (in situ form). The shear modulus and shear strength were test by V-notched specimens (bulk form) and thick adherend lap-shear (TALS) joint specimens (in situ form). The test results show that the elastic modulus provided by the manufacturer is too low, the dogbone specimen is better than the butt joint specimen to test the tensile strength and elastic modulus and the TALS joint specimen is better than the V-notched specimen to test the shear strength.

Measurement of Cement in Situ Stresses and Mechanical Properties Without Cooling or Depressurization

2021 ◽  
Author(s):  
Meng Meng ◽  
Luke Frash ◽  
James Carey ◽  
Wenfeng Li ◽  
Nathan Welch ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Axial Stress ◽  
Triaxial Compression ◽  
In Situ Measurement ◽  
Poisson's Ratio ◽  
Ambient Conditions

Abstract Accurate characterization of oilwell cement mechanical properties is a prerequisite for maintaining long-term wellbore integrity. The drawback of the most widely used technique is unable to measure the mechanical property under in situ curing environment. We developed a high pressure and high temperature vessel that can hydrate cement under downhole conditions and directly measure its elastic modulus and Poisson's ratio at any interested time point without cooling or depressurization. The equipment has been validated by using water and a reasonable bulk modulus of 2.37 GPa was captured. Neat Class G cement was hydrated in this equipment for seven days under axial stress of 40 MPa, and an in situ measurement in the elastic range shows elastic modulus of 37.3 GPa and Poisson's ratio of 0.15. After that, the specimen was taken out from the vessel, and setted up in the triaxial compression platform. Under a similar confining pressure condition, elastic modulus was 23.6 GPa and Possion's ratio was 0.26. We also measured the properties of cement with the same batch of the slurry but cured under ambient conditions. The elastic modulus was 1.63 GPa, and Poisson's ratio was 0.085. Therefore, we found that the curing condition is significant to cement mechanical property, and the traditional cooling or depressurization method could provide mechanical properties that were quite different (50% difference) from the in situ measurement.

scholarly journals Effect of cigarette smoking on nitric oxide, structural, and mechanical properties of mouse arteries

2006 ◽  
Vol 291 (5) ◽  
pp. H2354-H2361 ◽  
Author(s):  
X. Guo ◽  
M. J. Oldham ◽  
M. T. Kleinman ◽  
R. F. Phalen ◽  
G. S. Kassab
Keyword(s):  
Nitric Oxide ◽  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cigarette Smoking ◽  
Coronary Arteries ◽  
Short And Long Term ◽  
By Products ◽  
Enos Protein

Cigarette smoking (CS) is a major risk factor for vascular disease. The aim of this study was to quantitatively assess the influence of CS on mouse arteries. We studied the effect of short-term (6 wk) and long-term (16 wk) CS exposure on structural and mechanical properties of coronary arteries compared with that of control mice. We also examined the reversibility of the deleterious effects of CS on structural [e.g., wall thickness (WT)], mechanical (e.g., stiffness), and biochemical [e.g., nitric oxide (NO) by-products] properties with the cessation of CS. The left and right coronary arteries were cannulated in situ and mechanically distended. The stress, strain, elastic modulus, and WT of coronary arteries were determined. Western blot analysis was used to analyze endothelial NO synthase (eNOS) in the femoral and carotid arteries of the same mice, and NO by-products were determined by measuring the levels of nitrite. Our results show that the mean arterial pressure was increased by CS. Furthermore, CS significantly increased the elastic modulus, decreased stress and strain, and increased the WT and WT-to-radius ratio compared with those of control mice. The reduction of eNOS protein expression was found only after long-term CS exposure. Moreover, the NO metabolite was markedly decreased in CS mice after short- and long-term exposure of CS. These findings suggest that 16 wk of CS exposure can cause an irreversible deterioration of structural and elastic properties of mouse coronary arteries. The decrease in endothelium-derived NO in CS mice was seen to significantly correlate with the remodeling of arterial wall.

scholarly journals Mechanical Properties and In-Situ Deformation Imaging of Micro-Lattices Manufactured by Laser Based Powder Bed Fusion

2018 ◽  
Author(s):  
Anton Du Plessis ◽  
Dean-Paul Kouprianoff ◽  
Ina Yadroitsava ◽  
Igor Yadroitsev
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Lattice Structures ◽  
Powder Bed Fusion ◽  
Track Width ◽  
Powder Bed ◽  
Deformation Imaging ◽  
Small Pore ◽  
In Situ Deformation

This paper reports on the production and mechanical properties of Ti6Al4V micro-lattice structures, with strut thickness nearing the single-track width of the laser-based powder bed fusion (LPBF) system used. Besides providing new information on the mechanical properties and manufacturability of such thin-strut lattices, this paper also reports on the in-situ deformation imaging of micro-lattice structures with 6 unit cells in every direction. LPBF lattices are of interest for medical implants, due to the possibility of creating structures with an elastic modulus close to that of the bones and small pore sizes which allow effective osseointegration. In this work four different cubes were produced by laser powder bed fusion and subsequently analyzed using microCT, compression testing and one selected lattice was subjected to in-situ microCT imaging during compression. The in-situ imaging was performed at 4 steps during yielding. The results indicate that mechanical performance (elastic modulus and strength) correlate well with actual density and that this performance is remarkably good, despite the high roughness and irregularity of the struts at this scale. In-situ yielding is visually illustrated.

scholarly journals Chronic optical pacing conditioning of h-iPSC engineered cardiac tissues

2019 ◽  
Vol 10 ◽  
pp. 204173141984174 ◽  
Author(s):  
Marc Dwenger ◽  
William J Kowalski ◽  
Fei Ye ◽  
Fangping Yuan ◽  
Joseph P Tinney ◽  
...  
Keyword(s):  
Stem Cell ◽  
Electrical Stimulation ◽  
Pluripotent Stem Cell ◽  
Cardiac Tissue ◽  
Induced Pluripotent Stem Cell ◽  
Mechanical Stretch ◽  
In Vitro Models ◽  
Cardiac Tissues ◽  
Induced Pluripotent

The immaturity of human induced pluripotent stem cell derived engineered cardiac tissues limits their ability to regenerate damaged myocardium and to serve as robust in vitro models for human disease and drug toxicity studies. Several chronic biomimetic conditioning protocols, including mechanical stretch, perfusion, and/or electrical stimulation promote engineered cardiac tissue maturation but have significant technical limitations. Non-contacting chronic optical stimulation using heterologously expressed channelrhodopsin light-gated ion channels, termed optogenetics, may be an advantageous alternative to chronic invasive electrical stimulation for engineered cardiac tissue conditioning. We designed proof-of-principle experiments to successfully transfect human induced pluripotent stem cell derived engineered cardiac tissues with a desensitization resistant, chimeric channelrhodopsin protein, and then optically paced engineered cardiac tissues to accelerate maturation. We transfected human induced pluripotent stem cell engineered cardiac tissues using an adeno-associated virus packaged chimeric channelrhodopsin and then verified optically paced by whole cell patch clamp. Engineered cardiac tissues were then chronically optically paced above their intrinsic beat rates in vitro from day 7 to 14. Chronically optically paced resulted in improved engineered cardiac tissue electrophysiological properties and subtle changes in the expression of some cardiac relevant genes, though active force generation and histology were unchanged. These results validate the feasibility of a novel chronically optically paced paradigm to explore non-invasive and scalable optically paced–induced engineered cardiac tissue maturation strategies.

A method of monitoring water absorption in polymers using a depth sensing indentation system

1996 ◽  
Vol 11 (2) ◽  
pp. 529-536 ◽  
Author(s):  
I. A. Ashcroft ◽  
G. M. Spinks
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Water Absorption ◽  
Creep Strain ◽  
Epoxy Adhesive ◽  
Depth Sensing ◽  
Surface Layers ◽  
Depth Profiles ◽  
Hardness Depth

The mechanical properties of many polymers are known to change as they absorb water. This fact has been used to monitor the absorption of water into the surface layers of an epoxy adhesive with a depth sensing indentation system. Two methods have been demonstrated. The sample can be immersed in water for a period of time and then removed and tested in air. Alternatively, the sample can be tested in in situ. In the second method the transport of water through the adhesive can clearly be seen in hardness/depth profiles. Hardness, elastic modulus, and creep strain of the adhesive change with time until a stable value is reached, which corresponds to full plasticization of the adhesive to the influence depth of the indenter. The initial mechanical properties of the epoxy are mostly recovered on drying.

In Situ Measurement of Elastic and Frictional Properties Using Atomic Force Microscopy

2021 ◽  
pp. 1-10
Author(s):  
Ngoc-Phat Huynh ◽  
Tuan-Em Le ◽  
Koo-Hyun Chung
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscopy ◽  
Elastic Modulus ◽  
Force Microscopy ◽  
Frictional Properties ◽  
Atomic Force ◽  
Proposed Model ◽  
Significant Difference ◽  
Modulus Measurement

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.

Mechanical Properties of Biomimetic Composites for Bone Tissue Engineering

2004 ◽  
Vol 844 ◽  
Author(s):  
Devendra Verma ◽  
Kalpana S. Katti ◽  
Bedabibhas Mohanty
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Elastic Modulus ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Mechanical Response ◽  
Structural Disorder ◽  
Ex Situ ◽  
Porous Composites

ABSTRACTA biomimetic process involving in situ mineralization of hydroxyapatite (HAP) is used to design new composite biomaterials for bone tissue engineering. Surface and bulk properties of HAP composites have been studied for hydroxyapatite mineralized in absence (ex situ) of polyacrylic acid (PAAc) and in presence (in situ) of PAAc. XRD studies show existence of structural disorder within in situ HAP. It has been observed that PAAc increases the rate of crystallization. FTIR studies indicate calcium deficiency in structure of both in situ and ex situ HAP. PAAc provides favorable sites for nucleation of HAP. During crystallization of HAP, PAAc dissociates to form carboxylate ion, which binds to HAP. Porous and solid composites of in situ and ex situ HAP with polycaprolactone (PCL) in 50:50 ratio have been made to evaluate their applicability as bone scaffold. Mechanical tests on solid samples indicate ex situ HAP/PCL composites have higher elastic modulus (1.16 GPa) than in situ HAP/PCL composites (0.82 GPa). However, in case of porous composites, in situ HAP/PCL composites are found to have higher elastic modulus (29.5 MPa) than ex situ HAP/PCL composites (10.4 MPa). Nanoindentation tests were also performed at different loads to evaluate mechanical properties of the composites. In situ HAP mineralized using non-degradable polymers has thus been shown to improve mechanical response in porous composites.

Scale effect investigation of copper microwire's mechanical properties after in situ scanning electron microscope twisting

2018 ◽  
Vol 233 (10) ◽  
pp. 3670-3677
Author(s):  
Fengmei Xue ◽  
Haojian Lu ◽  
Yajing Shen
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Elastic Modulus ◽  
Scanning Electron Microscope ◽  
Strain Hardening Exponent ◽  
Surface Cracks ◽  
Manipulation System ◽  
Fracture Features ◽  
Scanning Electron

In this study, the mechanical property of copper microwire, a widely used material in our daily life, is investigated by subjecting it to in situ scanning electron microscope twisting based on a self-developed nanorobotic manipulation system. First, copper microwire is assembled on the nanorobotic system inside the scanning electron microscope, and then twisted clockwise and anticlockwise continuously from 0° to 360° until fracture. After that, the mechanical properties of elastic modulus, microhardness, yield stress, and the strain hardening exponent of the twisted sample are investigated by nanoindentation. The change in elastic modulus and indention hardness showed strong indentation size effects, because a large number of geometrically necessary dislocations were generated around the indenter. In addition, the fracture analysis indicated that the smaller the scale of the material, the more sensitive it was to surface cracks or defects. Ductile fracture features of the twisted sample appear due to the nucleation, growth, and coalescence of the microvoids.

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