Inverse Mechanical Characterization of Tissue Engineered Heart Valves

2008 ◽  
Author(s):  
Martijn A. J. Cox ◽  
Jeroen Kortsmit ◽  
Niels J. B. Driessen ◽  
Carlijn V. C. Bouten ◽  
Frank P. T. Baaijens
Keyword(s):  
Heart Valves ◽  
Soft Tissues ◽  
Mechanical Characterization ◽  
Tensile Tests ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Mechanical Conditioning ◽  
Indentation Tests ◽  
Tissue Engineered Heart Valves

Over the last few years, research interest in tissue engineering as an alternative for current treatment and replacement strategies for cardiovascular and heart valve diseases has significantly increased. In vitro mechanical conditioning is an essential tool for engineering strong implantable tissues [1]. Detailed knowledge of the mechanical properties of the native tissue as well as the properties of the developing engineered constructs is vital for a better understanding and control of the mechanical conditioning process. The nonlinear and anisotropic behavior of soft tissues puts high demands on their mechanical characterization. Current standards in mechanical testing of soft tissues include (multiaxial) tensile testing and indentation tests. Uniaxial tensile tests do not provide sufficient information for characterizing the full anisotropic material behavior, while biaxial tensile tests are difficult to perform, and boundary effects limit the test region to a small central portion of the tissue. In addition, characterization of the local tissue properties from a tensile test is non-trivial. Indentation tests may be used to overcome some of these limitations. Indentation tests are easy to perform and when indenter size is small relative to the tissue dimensions, local characterization is possible. We have demonstrated that by recording deformation gradients and indentation force during a spherical indentation test the anisotropic mechanical behavior of engineered cardiovascular constructs can be characterized [2]. In the current study this combined numerical-experimental approach is used on Tissue Engineered Heart Valves (TEHV).

Inverse Characterization of Nonlinear Anisotropic Mechanical Properties of Engineered Cardiovascular Tissues Using a Spherical Indentation Test

2007 ◽  
Author(s):  
M. A. J. Cox ◽  
R. A. Boerboom ◽  
C. V. C. Bouten ◽  
N. J. B. Driessen ◽  
F. P. T. Baaijens
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Indentation Test ◽  
Tensile Tests ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Mechanical Conditioning ◽  
Indentation Tests

Over the last few years, research interest in tissue engineering as an alternative for e.g. current treatment and replacement strategies for cardiovascular and heart valve diseaes has significantly increased. In vitro mechanical conditioning is an essential tool for engineering strong implantable tissues [1]. Detailed knowledge of the mechanical properties of the native tissue as well as the properties of the developing engineered constructs is vital for a better understanding and control of the mechanical conditioning process. The typical highly nonlinear and anisotropic behavior of soft tissues puts high demands on their mechanical characterization. Current standards in mechanical testing of soft tissues include (multiaxial) tensile testing and indentation tests. Uniaxial tensile tests do not provide sufficient information for characterizing the full anisotropic material behavior, while biaxial tensile tests are difficult to perform, and boundary effects limit the test region to a small central portion of the tissue. In addition, characterization of the local tissue properties from a tensile test is non-trivial. Indentation tests may be used to overcome some of these limitations. Indentation tests are easy to perform and when indenter size is small relative to the tissue dimensions, local characterization is possible. Therefore, we propose a spherical indentation test using finite deformations.

Development of a Global Indicator to Assess Mechanical Tests

2015 ◽  
Vol 651-653 ◽  
pp. 883-888
Author(s):  
Nelson Souto ◽  
Sandrine Thuillier ◽  
António Andrade-Campos
Keyword(s):  
Plane Strain ◽  
Simple Shear ◽  
Kinematic Hardening ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Strain Fields ◽  
Global Indicator

Full-field measurement methods have emerged in the last years and these methods are characterized by directly providing displacement and strain fields for all points over the specimen surface. Thus, the design of heterogeneous tests can be performed for material parameter identification purposes since the inhomogeneous strain fields can be measured. However, (i) no defined criterion yet exists for designing new heterogeneous tests, (ii) it is rather difficult to compare and rate different tests and (iii) a quantitative way to define the best test for material behavior characterization of sheet metals has yet to be proposed. Due to this, the goal of this work is the development of a global indicator able to assess mechanical tests. The proposed indicator quantifies the strain state range, the deformation heterogeneity and the strain level achieved in the test, based on a continuous evaluation of the strain field up to rupture. This global indicator was applied to rank some classical tests, such as uniaxial tensile, simple shear, plane strain and biaxial tensile tests. These tests were carried out numerically by reproducing the virtual behavior of DC04 mild steel. A constitutive model composed by the non-quadratic Yld2004-18p yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion was used. The performance of the tests was compared with the indicator and a ranking was established. The results obtained show that biaxial tension is the test providing more information for the mechanical behavior characterization of the material. It was also verified that plane strain test presents a better performance than simple shear and uniaxial tensile tests.

Non-Destructive and Non-Invasive Assessment of Mechanical Properties in Heart Valve Tissue Engineering

2008 ◽  
Author(s):  
Jeroen Kortsmit ◽  
Niels J. B. Driessen ◽  
Marcel C. M. Rutten ◽  
Frank P. T. Baaijens
Keyword(s):  
Mechanical Properties ◽  
Heart Valve ◽  
Heart Valves ◽  
Tensile Tests ◽  
Numerical Approach ◽  
Non Invasive ◽  
Indentation Tests ◽  
Tissue Engineered Heart Valves ◽  
End Stage ◽  
Non Destructive

Despite recent progress, mechanical properties of tissue engineered heart valves still lack mechanical strength compared to native aortic valves [1]. Although cyclic tissue straining in bioreactor systems is known to enhance tissue formation [2], specific optimal loading protocols have not yet been defined. To get a better insight in the effects of mechanical loading on tissue development, mechanical behavior of tissue constructs should be monitored and controlled during culture. However, currently used methods for mechanical characterization (e.g. tensile tests, indentation tests) are destructive and can therefore only be performed at the end stage of tissue culture. An experimental-numerical approach was previously proposed by which leaflet deformation was assessed during culture in a bioreactor system, real-time and non-invasively [3]. Further development of this approach now enables a non-invasive and non-destructive assessment of mechanical properties of engineered heart valve leaflets.

Design and validation of a modular micro-robotic system for the mechanical characterization of soft tissues

2021 ◽  
Author(s):  
Andrea Acuna ◽  
Julian M. Jimenez ◽  
Naomi Deneke ◽  
Sean M. Rothenberger ◽  
Sarah Libring ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Mechanical Characterization ◽  
Robotic System

Mechanical Characterization of Metal Sheets by Means of Double Indentation

2007 ◽  
Vol 344 ◽  
pp. 127-134 ◽  
Author(s):  
Fabrizio Quadrini ◽  
Loredana Santo ◽  
Erica Anna Squeo
Keyword(s):  
Small Diameter ◽  
Tensile Tests ◽  
Testing Rate ◽  
Metal Sheets ◽  
Indentation Tests ◽  
Tensile Data ◽  
On Line ◽  
Fast Procedure ◽  
Non Destructive

An easy and innovative technique for metal sheet characterization is described. A double indentation is performed on sheets by means of two co-axial small diameter flat indenters made of WC. A very small indentation is left on the sheet, so as to consider this technique a non destructive one, particularly suitable for on-line application. The proposed method was tested on sheets of aluminum alloy (6082 T6) with several thicknesses (nominally 0.6, 0.8, 1 and 1.5 mm). Double indentations were performed changing indenter diameter (1 and 2 mm) and testing rate (from 0.05 to 1 mm/min). In order to make a comparison with indentation tests, flat specimens were cut from the same sheets and standard tensile tests were performed. A very good correlation was found between indentation and tensile test results, showing the effectiveness of the proposed method. A suitable data normalization is necessary to correctly compare indentation and tensile data. The best results were obtained using the smaller diameter indenter. The testing rate seems to be not relevant in the experimented range, suggesting that a fast procedure can be defined on purpose for on-line application.

Dental Pulp Stem Cells for Tissue Engineered Heart Valve

2020 ◽  
Author(s):  
Soontaree Petchdee ◽  
Wilairat Chumsing ◽  
Suruk Udomsom ◽  
Kittiya Thunsiri
Keyword(s):  
Stem Cells ◽  
Mitral Valve ◽  
Heart Valve ◽  
Heart Valves ◽  
Cell Types ◽  
Tensile Tests ◽  
Deciduous Teeth ◽  
Essential Information ◽  
Acquired Heart Disease ◽  
Tissue Engineered Heart Valves

Myxomatous mitral valve degeneration is the most acquired heart disease in dogs. To reduce the clinical progression of mitral valve degeneration and achieve the hemodynamic outcomes, many medical or surgical treatments have been motivated. The objectives of this study is to investigate the suitability of puppy deciduous teeth stem cells as a cell source for tissue engineered heart valves in dog with degenerative valve disease. Puppy deciduous teeth stem cells (pDSCs) were seeded on the scaffolds which made from polylactic acid (PLA), polycaprolactone (PLC) and silicone. The mechanical properties of the tissue engineered heart valves leaflets were characterized by biaxial tensile tests. Results showed that, deciduous teeth stem cells capable of differentiating into a variety of cell types. However, the ability of puppy deciduous teeth stem cells to differentiate declined with increasing passage number which correspond to the number of protein surface marker detection have been shown to decrease substantially by the fifth passage. PLA scaffold is significantly higher tensile strength than other materials. However, silicone showed the highest flaccidity. The results from this study may provide high regenerative capability and the essential information for future directions of heart valve tissue engineering.

Mechanical Characterization of Polymer Nanowires Using MEMS

2006 ◽  
Author(s):  
B. A. Samuel ◽  
Bo Yi ◽  
R. Rajagopalan ◽  
H. C. Foley ◽  
M. A. Haque
Keyword(s):  
Mechanical Properties ◽  
Tensile Testing ◽  
Furfuryl Alcohol ◽  
Mechanical Characterization ◽  
Uniaxial Tensile ◽  
Testing Device ◽  
Uniaxial Tensile Testing ◽  
Polymer Nanowires

We present results on the mechanical properties of single freestanding poly-furfuryl alcohol (PFA) nanowires (aspect ratio > 50, diameters 100–300 nm) from experiments conducted using a MEMS-based uniaxial tensile testing device in-situ inside the SEM. The specimens tested were pyrolyzed PFA nanowires (pyrolyzed at 800° C).

scholarly journals Recyclable Organocatalyzed Poly(Thiourethane) Covalent Adaptable Networks

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2913
Author(s):  
Francesco Gamardella ◽  
Sara Muñoz ◽  
Silvia De la Flor ◽  
Xavier Ramis ◽  
Angels Serra
Keyword(s):  
Stress Relaxation ◽  
Mechanical Characterization ◽  
Tensile Tests ◽  
Thermomechanical Analysis ◽  
Hexamethylene Diisocyanate ◽  
Relaxation Rates ◽  
Ftir Studies ◽  
New Type ◽  
And Performance

A new type of tetraphenylborate salts derived from highly basic and nucleophilic amines, namely 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) and triazabicyclodecene (TBD), was applied to the preparation of networked poly(thiourethane)s (PTUs), which showed a vitrimer-like behavior, with higher stress-relaxation rates than PTUs prepared by using dibutyl thin dilaurate (DBTDL) as the catalyst. The use of these salts, which release the amines when heated, instead of the pure amines, allows the formulation to be easily manipulated to prepare any type of samples. The materials prepared from stoichiometric mixtures of hexamethylene diisocyanate (HDI), trithiol (S3) and with a 10% of molar excess of isocyanate or thiol were characterized by FTIR, thermomechanical analysis, thermogravimetry, stress-relaxation tests and tensile tests, thus obtaining a complete thermal and mechanical characterization of the materials. The recycled materials obtained by grinding the original PTUs and hot-pressing the small pieces in the optimized time and temperature conditions were fully characterized by mechanical, thermomechanical and FTIR studies. This allowed us to confirm their recyclability, without appreciable changes in the network structure and performance. From several observations, the dissociative interchange trans-thiocarbamoylation mechanism was evidenced as the main responsible of the topological rearrangements at high temperature, resulting in a vitrimeric-like behavior.

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