Comparison of elastic and tactile behavior of human skin and elastomeric materials through tribological tests (original) (raw)
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Journal of Textile Engineering
A texture that has a microstructure with arrangements of cyclic micrometric projections generates various effects on human skin owing to mutual contact. The mechanical effects, such as stimulus of the skin, owing to contact with such microstructures are complicated because of the skin structure itself. The evaluation of the effects is necessary for control and design of the microstructure. Since experimental measurements are relatively difficult, numerical analyses are effective for detailing and objectively evaluating the mechanical effects on human skin. For this reason, numerical analyses of the effects of surface textures on skin were performed in this study. In particular, differences caused by cyclic variations of the texture were ascertained for the evaluation. Pressure, von Mises stress, etc., of the skin sensory organs were ascertained by performing numerical modeling of the situations where the texture touches the skin. The results of the analyses showed several characteristic effects such as negative pressure at the boundary of the horny layer and epidermis. The negative pressure was increased according to the increase of texture cycle. The von Mises stress at shallow positions changed characteristically, whereas von Mises stress at deep positions decreased monotonously with an increase of texture cycle. The von Mises stress at a shallow position of the dermis had a local minimum value for a particular texture cycle without monotonous increasing or decreasing.
Computational and Mathematical Methods in Medicine, 2013
This paper proposes a triphasic model of intact skin in vivo based on a general phenomenological thermohydromechanical and physicochemical (THMPC) approach of heterogeneous media. The skin is seen here as a deforming stratified medium composed of four layers and made out of different fluid-saturated materials which contain also an ionic component. All the layers are treated as linear, isotropic materials described by their own behaviour law. The numerical simulations of in vivo indentation test performed on human skin are given. The numerical results correlate reasonably well with the typical observations of indented human skin. The discussion shows the versatility of this approach to obtain a better understanding on the mechanical behaviour of human skin layers separately.
Influence of indentation test factors on the mechanical response of the skin
Universitas Scientiarum, 2019
This study proposes in vivo tests and design of experiments to determine the influence of experimental factors on the mechanical response of the soft tissue. The experimental factors considered are: room temperature (A), indentation velocity (B), indenter temperature (C), pump pressure (D) and muscle activation (E). An inverse method was developed to obtain the constants for constitutive equations of a multilayer biological model (skin, hypodermis, and muscle) through the use of indentation tests in combination with a finite element method. For each combination of the experimental factors, two groups of constants were established from the inverse method. Sixteen combinations of experimental conditions and their corresponding constants for the Mooney-Rivlin constitutive equations were obtained to be used in further numerical models. The factor D and factor interactions ADE, CDE, and ACDE were statistically significant with respect to skin mechanical response. Therefore, it can be con...
Journal of Biomechanics, 2006
This study proposes a new method to determine the mechanical properties of human skin by the use of the indentation test [Pailler-Mattei, 2004. Caractérisation mécanique et tribologique de la peau humaine in vivo, Ph.D. Thesis, ECL-no. 2004-31; Pailler-Mattei, Zahouani, 2004. Journal of Adhesion Science and Technology 18, 1739-1758]. The principle of the measurements consists in applying an in vivo compressive stress [Zhang et al., 1994. Proceedings of the Institution of Mechanical Engineers 208, 217-222; Bosboom et al., 2001. Journal of Biomechanics 34, 1365-1368; Oomens et al., 1984. Selected Proceedings of Meetings of European Society of Biomechanics, pp. 227-232; Oomens et al., 1987. Journal of Biomechanics 20(9), 877-885] on the skin tissue of an individual's forearm. These measurements show an increase in the normal contact force as a function of the indentation depth. The interpretation of such results usually requires a long and tedious phenomenological study. We propose a new method to determine the mechanical parameters which control the response of skin tissue. This method is threefold: experimental, numerical, and comparative. It consists combining experimental results with a numerical finite elements model in order to find out the required parameters. This process uses a scheme of extended Kalman filters (EKF) [Gu et al., 2003. Materials Science and Engineering A345, 223-233; Nakamura et al., 2000. Acta Mater 48, 4293-4306; Leustean and Rosu, 2003. Certifying Kalman filters. RIACS Technical Report 03.02, 27pp. http://gureni.cs.uiuc.edu/\~grosu/download/luta + leo.pdf; Welch and Bishop, An introduction to Kalman filter, University of North Carolina at Chapel Hill, 16p. http://www.cs.unc.edu/\~welch/kalman/\]. The first results presented in this study correspond to a simplified numerical modeling of the global system. The skin is assumed to be a semi-infinite layer with an isotropic linear elastic mechanical behavior [Zhang et al., 1994. Proceedings of the Institution of Mechanical Engineers 208, 217-222] This analysis will be extended to more realistic models in further works.
Procedia Engineering, 2015
Introduction: In vivo tests and design of experiment were carried out to determine the influence of indenter diameter and temperature on the mechanical response of soft tissue. Material and methods: This study proposes an analysis to obtain the Young's modulus of skin through the use of indentation tests in combination with the Hertz's theory for contact. A design of experiments was developed to determine the incidence of two factors: temperature and indenter diameter, on the mechanical behavior of the skin. Results: The factors and their interactions are not statistically significant with a p-value higher than 0.05. Discussion/conclusions: The mean value (±SD) obtained for all eight measurements on the volunteer subject was 28.5 ± 6.9 kPa for E, Young's modulus.
HAL (Le Centre pour la Communication Scientifique Directe), 2013
Cette contribution propose un modèle de milieu multi-phasique appliqué à l'étude de la peau humaine in vivo. La peau est considérée comme un milieu stratifié présentant trois couches (le stratum corneum, l'épiderme vivant et le derme) pour lequel les constituants présents sont trois solides, un fluide et des ions. Chaque couche est considérée comme un solide non-linéaire isotrope hyper-élastique de Mooney-Rivlin pouvant expérimenter de grands déplacements. Des simulations numériques sont présentées. La discussion permet de souligner l'aide de telles études pour obtenir des informations sur les propriétés mécaniques des différentes couches de la peau humaine in vivo.
The conformance test for robotic/prosthetic fingertip skins
2006
Although the requirements for robotic and prosthetic skins may considerably differ, conformance is a critical property when a tactile sensory system is embedded on the skin. The skin's inability to deflect or adapt to the surface of an object will prevent the spatial features to be transmitted to the embedded tactile sensors. By characterizing viscoelastic materials like Technogel®, silicone and polyurethane, and applying their material coefficients to a finite element model, comparisons were made possible with the experimental surface deflection of a human fingertip that was indented by a wedge. Simulations showed that the silicone as the inner layer, and polyurethane or Technogel® as the outer layer offered the optimal combination that approximates the human fingertip's conformance.
Materials used to simulate physical properties of human skin
Skin Research and Technology, 2015
Background: For many applications in research, material development and testing, physical skin models are preferable to the use of human skin, because more reliable and reproducible results can be obtained. Purpose: This article gives an overview of materials applied to model physical properties of human skin to encourage multidisciplinary approaches for more realistic testing and improved understanding of skin-material interactions. Methods: The literature databases Web of Science, PubMed and Google Scholar were searched using the terms 'skin model', 'skin phantom', 'skin equivalent', 'synthetic skin', 'skin substitute', 'artificial skin', 'skin replica', and 'skin model substrate.' Articles addressing material developments or measurements that include the replication of skin properties or behaviour were analysed. Results: It was found that the most common materials used to simulate skin are liquid suspensions, gelatinous substances, elastomers, epoxy resins, metals and textiles. Nano-and micro-fillers can be incorporated in the skin models to tune their physical properties. Conclusion: While numerous physical skin models have been reported, most developments are research field-specific and based on trial-and-error methods. As the complexity of advanced measurement techniques increases, new interdisciplinary approaches are needed in future to achieve refined models which realistically simulate multiple properties of human skin.
2011
This article presents the developmental process of a new tactile sensor. The sensor was based on the use of light-emitting diode (LED) phototransistor couples and a silicone rubber layer positioned above the optoelectronics devices. The optoelectronic components were organized in a matrix structure. For each couple, the LED illuminated the reflective surface, which coincided with the bottom facet of the deformable layer. Practically, the deformable layer transduced an external force into a displacement variation of its bottom facet through its stiffness. An external force applied to the deformable layer produced local variations of the bottom surface of the elastic material, and the couples of optical devices measured the vertical deformations in a discrete number of points. In particular, these vertical displacements produced a variation of the reflected light intensity and, accordingly, of the photocurrent measured by the photodetector. The realized prototype was designed and optimized through finite element analysis. A calibration procedure is also presented, whose results demonstrate the ability of the sensor to reconstruct the contact point and also the normal and tangential components of the contact force.