Experimental and theoretical analyses of the age-dependent large-strain behavior of Sylgard 184 (10:1) silicone elastomer

Hopf, Raoul; Bernardi, Laura; Menze, J.; Zündel, Manuel; Mazza, Edoardo; Ehret, Alexander E.

doi:10.1016/j.jmbbm.2016.02.022

Cited by 87 publications

(69 citation statements)

References 64 publications

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“…Samples were subjected to a controlled tensile displacement of 0.1 mm s −1 until failure in a saline bath (NaCl, 154 mmol/L) at room temperature. Local (true) strains were determined from images of the deforming specimens (time lapse) via point tracking with a custom-written code [26] or similarly using an ImageJ plugin trackmate. Both 1st Piola-Kirchhoff (σ pK1 ) and Cauchy (σ C ) stresses were computed for each specimen according to the following relations: σ pK1 = F c /(w 0 t 0 ), and σ C = F c /(w c t c ), F being the measured force throughout the tensile test, w the specimen width, and t its thickness where the subscripts 0 and c refer to the initial (reference) and the current (deformed) configurations, respectively.…”

Section: Commercial Bioinksmentioning

confidence: 99%

Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

et al. 2016

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Biofabrication techniques including threedimensional bioprinting could be used one day to fabricate living, patient-specific tissues and organs for use in regenerative medicine. Compared to traditional casting and molding methods, bioprinted structures can be much more complex, containing for example multiple materials and cell types in controlled spatial arrangement, engineered porosity, reinforcement structures and gradients in mechanical properties. With this complexity and increased function, however, comes the necessity to develop guidelines to standardize the bioprinting process, so printed grafts can safely enter the clinics. The bioink material must firstly fulfil requirements for biocompatibility and flow. Secondly, it is important to understand how process parameters affect the final mechanical properties of the printed graft. Using a gellan-alginate physically crosslinked bioink as an example, we show shear thinning and shear recovery properties which allow good printing resolution. Printed tensile specimens were used to systematically assess effect of line spacing, printing direction and crosslinking conditions. This standardized testing allowed direct comparison between this bioink and three commercially-available products. Bioprinting is a promising, yet complex fabrication method whose outcome is sensitive to a range of process parameters. This study provides the foundation for highly needed best practice guidelines for reproducible and safe bioprinted grafts.

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Section: Commercial Bioinksmentioning

confidence: 99%

Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

et al. 2016

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“…This method was adapted from ref. 52 and yielded membranes with an elastic modulus of 1.09 MPa53. The thickness h was verified by determining cross sections at 8 to 9 different, preselected points with a microscope in brightfield mode (LSM 5 Pascal, Carl Zeiss GmbH, Jena, Germany).…”

Section: Methodsmentioning

confidence: 99%

“…8-node biquadratic axisymmetric quadrilateral, hybrid, linear pressure, reduced integration elements were selected for all computations. The constitutive model applied for the PDMS membrane was the one determined in our previous investigations on the multiaxial large strain mechanical behavior of the material53. The membrane edge was constrained in the vertical and radial direction, to simulate the boundary conditions applied in the real system.…”

Section: Methodsmentioning

confidence: 99%

A Novel Bioreactor System for the Assessment of Endothelialization on Deformable Surfaces

Bachmann

Bernardi

Loosli

et al. 2016

Sci Rep

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The generation of a living protective layer at the luminal surface of cardiovascular devices, composed of an autologous functional endothelium, represents the ideal solution to life-threatening, implant-related complications in cardiovascular patients. The initial evaluation of engineering strategies fostering endothelial cell adhesion and proliferation as well as the long-term tissue homeostasis requires in vitro testing in environmental model systems able to recapitulate the hemodynamic conditions experienced at the blood-to-device interface of implants as well as the substrate deformation. Here, we introduce the design and validation of a novel bioreactor system which enables the long-term conditioning of human endothelial cells interacting with artificial materials under dynamic combinations of flow-generated wall shear stress and wall deformation. The wall shear stress and wall deformation values obtained encompass both the physiological and supraphysiological range. They are determined through separate actuation systems which are controlled based on validated computational models. In addition, we demonstrate the good optical conductivity of the system permitting online monitoring of cell activities through live-cell imaging as well as standard biochemical post-processing. Altogether, the bioreactor system defines an unprecedented testing hub for potential strategies toward the endothelialization or re-endothelialization of target substrates.

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“…Finite element analysis (FEA) of arbitrary contact interactions with the sensor's soft surface requires material models that account for geometrical and material nonlinearities. Soft elastomers are often modeled as hyperelastic materials [26], and finding a suitable model formulation and corresponding parameters generally necessitates experimental data from both uniaxial and biaxial stress states [27], [28]. To this end, a large-strain multiaxial characterization of the two most compliant materials, the Ecoflex GEL and the Elastosil 25:1, is performed.…”

Section: Materials Characterizationmentioning

confidence: 99%

Ground Truth Force Distribution for Learning-Based Tactile Sensing: A Finite Element Approach

et al. 2019

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Skin-like tactile sensors provide robots with rich feedback related to the force distribution applied to their soft surface. The complexity of interpreting raw tactile information has driven the use of machine learning algorithms to convert the sensory feedback to the quantities of interest. However, the lack of ground truth sources for the entire contact force distribution has mainly limited these techniques to the sole estimation of the total contact force and the contact center on the sensor's surface. The method presented in this article uses a finite element model to obtain ground truth data for the three-dimensional force distribution. The model is obtained with state-of-the-art material characterization methods and is evaluated in an indentation setup, where it shows high agreement with the measurements retrieved from a commercial force-torque sensor. The proposed technique is applied to a vision-based tactile sensor, which aims to reconstruct the contact force distribution purely from images. Thousands of images are matched to ground truth data and are used to train a neural network architecture, which is suitable for real-time predictions.

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Experimental and theoretical analyses of the age-dependent large-strain behavior of Sylgard 184 (10:1) silicone elastomer

Cited by 87 publications

References 64 publications

Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

A Novel Bioreactor System for the Assessment of Endothelialization on Deformable Surfaces

Ground Truth Force Distribution for Learning-Based Tactile Sensing: A Finite Element Approach

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