Influence of epidermal hydration on the friction of human skin against textiles.
06 Nov 2008-Journal of the Royal Society Interface (The Royal Society)-Vol. 5, Iss: 28, pp 1317-1328
TL;DR: Increasing skin hydration seems to cause gender-specific changes in the mechanical properties and/or surface topography of human skin, leading to skin softening and increased real contact area and adhesion.
Abstract: Friction and shear forces, as well as moisture between the human skin and textiles are critical factors in the formation of skin injuries such as blisters, abrasions and decubitus. This study investigated how epidermal hydration affects the friction between skin and textiles. The friction between the inner forearm and a hospital fabric was measured in the natural skin condition and in different hydration states using a force plate. Eleven males and eleven females rubbed their forearm against the textile on the force plate using defined normal loads and friction movements. Skin hydration and viscoelasticity were assessed by corneometry and the suction chamber method, respectively. In each individual, a highly positive linear correlation was found between skin moisture and friction coefficient (COF). No correlation was observed between moisture and elasticity, as well as between elasticity and friction. Skin viscoelasticity was comparable for women and men. The friction of female skin showed significantly higher moisture sensitivity. COFs increased typically by 43% (women) and 26% (men) when skin hydration varied between very dry and normally moist skin. The COFs between skin and completely wet fabric were more than twofold higher than the values for natural skin rubbed on a dry textile surface. Increasing skin hydration seems to cause gender-specific changes in the mechanical properties and/or surface topography of human skin, leading to skin softening and increased real contact area and adhesion.
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University of Groningen1, PSL Research University2, École centrale de Lyon3, Delft University of Technology4, University of Padua5, Imperial College London6, Luleå University of Technology7, IMT Institute for Advanced Studies Lucca8, Technical University of Denmark9, University of Cape Town10, University of Southampton11, École Polytechnique Fédérale de Lausanne12, Aarhus University13, King's College London14, Hamburg University of Technology15, Czech Technical University in Prague16, Instituto Politécnico Nacional17, Polish Academy of Sciences18, University of Turin19, University of Trento20, Queen Mary University of London21, Saarland University22
TL;DR: This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales, and proposes some research directions.
347 citations
Cites background from "Influence of epidermal hydration on..."
...38 It is widely accepted that skin friction is made of deformation-induced and adhesion components [511,692-695] but, up to now [512], adhesion-induced friction has been deemed to be the dominant contributor to macroscopic friction....
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...[693] Gerhardt LC, Strassle V, Lenz A, Spencer ND, Derler S....
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TL;DR: In this paper, the authors discuss the current knowledge on the tribology of human skin and present an analysis of the available experimental results for skin friction coefficients, showing that substantial variations are a characteristic feature of friction coefficients measured for skin and that differences in skin hydration are the main cause thereof, followed by the influences of surface and material properties of contacting materials.
Abstract: In this review, we discuss the current knowledge on the tribology of human skin and present an analysis of the available experimental results for skin friction coefficients. Starting with an overview on the factors influencing the friction behaviour of skin, we discuss the up-to-date existing experimental data and compare the results for different anatomical skin areas and friction measurement techniques. For this purpose, we also estimated and analysed skin contact pressures applied during the various friction measurements. The detailed analyses show that substantial variations are a characteristic feature of friction coefficients measured for skin and that differences in skin hydration are the main cause thereof, followed by the influences of surface and material properties of the contacting materials. When the friction coefficients of skin are plotted as a function of the contact pressure, the majority of the literature data scatter over a wide range that can be explained by the adhesion friction model. The case of dry skin is reflected by relatively low and pressure-independent friction coefficients (greater than 0.2 and typically around 0.5), comparable to the dry friction of solids with rough surfaces. In contrast, the case of moist or wet skin is characterised by significantly higher (typically >1) friction coefficients that increase strongly with decreasing contact pressure and are essentially determined by the mechanical shear properties of wet skin. In several studies, effects of skin deformation mechanisms contributing to the total friction are evident from friction coefficients increasing with contact pressure. However, the corresponding friction coefficients still lie within the range delimited by the adhesion friction model. Further research effort towards the analysis of the microscopic contact area and mechanical properties of the upper skin layers is needed to improve our so far limited understanding of the complex tribological behaviour of human skin.
341 citations
Cites background or result from "Influence of epidermal hydration on..."
...On the other hand, a linear increase in measured friction coefficients could also be associated with the effects of skin hydration [48, 110]....
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...In the case of friction between a cotton-polyester fabric and moist skin [48], we concluded that capillary bridges (fluid menisci) formed by superficial water micro-droplets played an unimportant role for the increase in friction, assuming complete removal of excess water from the skin surface due to the water-absorbing/hygroscopic nature of the studied textile....
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...We systematically varied the hydration state of the skin of the volar forearm in 22 subjects and found a highly positive linear correlation between skin moisture and friction coefficients against textiles [48]....
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...We [48] and others [51] attributed the large increase in skin friction with moisture to the plasticizing effect of water, leading to smoothening of skin roughness asperities and consequently a greater real contact area (RCA)....
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...Linear [5, 48], power-law [49], exponential [108] and bell-shaped relationships [109, 110] between skin hydration and friction have been reported....
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TL;DR: Many aspects of both grip function and tactile perception depend on complex frictional interactions occurring in the contact zone of the finger pad, which is the subject of the current review.
Abstract: Many aspects of both grip function and tactile perception depend on complex frictional interactions occurring in the contact zone of the finger pad, which is the subject of the current review. While it is well established that friction plays a crucial role in grip function, its exact contribution for discriminatory touch involving the sliding of a finger pad is more elusive. For texture discrimination, it is clear that vibrotaction plays an important role in the discriminatory mechanisms. Among other factors, friction impacts the nature of the vibrations generated by the relative movement of the fingertip skin against a probed object. Friction also has a major influence on the perceived tactile pleasantness of a surface. The contact mechanics of a finger pad is governed by the fingerprint ridges and the sweat that is exuded from pores located on these ridges. Counterintuitively, the coefficient of friction can increase by an order of magnitude in a period of tens of seconds when in contact with an impermeably smooth surface, such as glass. In contrast, the value will decrease for a porous surface, such as paper. The increase in friction is attributed to an occlusion mechanism and can be described by first-order kinetics. Surprisingly, the sensitivity of the coefficient of friction to the normal load and sliding velocity is comparatively of second order, yet these dependencies provide the main basis of theoretical models which, to-date, largely ignore the time evolution of the frictional dynamics. One well-known effect on taction is the possibility of inducing stick–slip if the friction decreases with increasing sliding velocity. Moreover, the initial slip of a finger pad occurs by the propagation of an annulus of failure from the perimeter of the contact zone and this phenomenon could be important in tactile perception and grip function.
238 citations
TL;DR: Effective integration between the electronic components with garments, human skin, and living organisms is illustrated, presenting multifunctional platforms with self-powered potential for human-robot interactions and biomedicine.
Abstract: Soft robotics inspired by the movement of living organisms, with excellent adaptability and accuracy for accomplishing tasks, are highly desirable for efficient operations and safe interactions with human. With the emerging wearable electronics, higher tactility and skin affinity are pursued for safe and user-friendly human-robot interactions. Fabrics interlocked by fibers perform traditional static functions such as warming, protection, and fashion. Recently, dynamic fibers and fabrics are favorable to deliver active stimulus responses such as sensing and actuating abilities for soft-robots and wearables. First, the responsive mechanisms of fiber/fabric actuators and their performances under various external stimuli are reviewed. Fiber/yarn-based artificial muscles for soft-robots manipulation and assistance in human motion are discussed, as well as smart clothes for improving human perception. Second, the geometric designs, fabrications, mechanisms, and functions of fibers/fabrics for sensing and energy harvesting from the human body and environments are summarized. Effective integration between the electronic components with garments, human skin, and living organisms is illustrated, presenting multifunctional platforms with self-powered potential for human-robot interactions and biomedicine. Lastly, the relationships between robotic/wearable fibers/fabrics and the external stimuli, together with the challenges and possible routes for revolutionizing the robotic fibers/fabrics and wearables in this new era are proposed.
207 citations
TL;DR: Several biophysical properties of the skin vary among different gender, age groups, and body locations, and there were significant differences between the hydration, melanin index, and elasticity of different age groups.
Abstract: Background. Understanding the physiological, chemical, and biophysical characteristics of the skin helps us to arrange a proper approach to the management of skin diseases. Objective. The aim of this study was to measure 6 biophysical characteristics of normal skin (sebum content, hydration, transepidermal water loss (TEWL), erythema index, melanin index, and elasticity) in a normal population and assess the effect of sex, age, and body location on them. Methods. Fifty healthy volunteers in 5 age groups (5 males and females in each) were enrolled in this study. A multifunctional skin physiology monitor (Courage & Khazaka electronic GmbH, Germany) was used to measure skin sebum content, hydration, TEWL, erythema index, melanin index, and elasticity in 8 different locations of the body. Results. There were significant differences between the hydration, melanin index, and elasticity of different age groups. Regarding the locations, forehead had the highest melanin index, where as palm had the lowest value. The mean values of erythema index and melanin index and TEWL were significantly higher in males and anatomic location was a significant independent factor for all of 6 measured parameters. Conclusion. Several biophysical properties of the skin vary among different gender, age groups, and body locations.
174 citations
Cites background from "Influence of epidermal hydration on..."
...It displays hydration measurements in system-specific arbitrary units [5]....
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References
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Book•
01 Jul 1981TL;DR: This chapter discusses the mechanics of Erythrocytes, Leukocytes, and Other Cells, and their role in Bone and Cartilage, and the properties of Bioviscoelastic Fluids, which are a by-product of these cells.
Abstract: Prefaces. 1. Introduction: A sketch of the History and Scope of the Field. 2. The Meaning of the Constitutive Equation. 3. The Flow Properties of Blood. 4. Mechanics of Erythrocytes, Leukocytes, and Other Cells. 5. Interaction of Red Blood Cells with Vessel Wall, and Wall Shear with Endothelium. 6 Bioviscoelastic Fluids. Bioviscoelastic Solids. 8. Mechanical Properties and Active Remodeling of Blood Vessels. 9. Skeletal Muscle. 10. Heart Muscle. 11. Smooth Muscles. 12. Bone and Cartilage. Indices
6,027 citations
TL;DR: In this article, the authors present a sketch of the history and scope of the field of bio-physiology and discuss the meaning of the Constitutive Equation and the flow properties of blood.
Abstract: Prefaces. 1. Introduction: A sketch of the History and Scope of the Field. 2. The Meaning of the Constitutive Equation. 3. The Flow Properties of Blood. 4. Mechanics of Erythrocytes, Leukocytes, and Other Cells. 5. Interaction of Red Blood Cells with Vessel Wall, and Wall Shear with Endothelium. 6 Bioviscoelastic Fluids. Bioviscoelastic Solids. 8. Mechanical Properties and Active Remodeling of Blood Vessels. 9. Skeletal Muscle. 10. Heart Muscle. 11. Smooth Muscles. 12. Bone and Cartilage. Indices
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TL;DR: A heterogeneous two-compartment model of the stratum corneum that ascribes a special role for intercellular lipids in the regulation of stratum Corneum barrier function and desquamation is proposed.
1,221 citations
TL;DR: This book is the second edition of the first volume in a series of three volumes by Y. C. Fung on biomechanics that summarizes the application of an enormously wide spectrum of mechanics and thermodynamics to physiology and the engineering of biologically related problems.
1,025 citations
"Influence of epidermal hydration on..." refers background in this paper
...Such a linear behaviour was not expected because nonlinear material behaviour is typical for living tissues in general and soft tissues in particular (Fung 1993)....
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TL;DR: The present paper reviews the current understanding of the biology of the stratum corneum, particularly its homeostatic mechanisms of hydration, and discusses how each maturation step leading to the formation of an effective moisture barrier—including corneocyte strengthening, lipid processing, and NMF generation—is influenced by the level of SC hydration.
Abstract: Over the past decade, great progress has been made toward elucidating the structure and function of the stratum corneum (SC), the outermost layer of the epidermis. SC cells (corneocytes) protect against desiccation and environmental challenge by regulating water flux and retention. Maintenance of an optimal level of hydration by the SC is largely dependent on several factors. First, intercellular lamellar lipids, organized predominantly in an orthorhombic gel phase, provide an effective barrier to the passage of water through the tissue. Secondly, the diffusion path length also retards water loss, since water must traverse the tortuous path created by the SC layers and corneocyte envelopes. Thirdly, and equally important, is natural moisturizing factor (NMF), a complex mixture of low-molecular-weight, water-soluble compounds first formed within the corneocytes by degradation of the histidine-rich protein known as filaggrin. Each maturation step leading to the formation of an effective moisture barrier--including corneocyte strengthening, lipid processing, and NMF generation--is influenced by the level of SC hydration. These processes, as well as the final step of corneodesmolysis that mediates exfoliation, are often disturbed upon environmental challenge, resulting in dry, flaky skin conditions. The present paper reviews our current understanding of the biology of the SC, particularly its homeostatic mechanisms of hydration.
738 citations
"Influence of epidermal hydration on..." refers background in this paper
...NMF generation will be suppressed or even inhibited if skin is sufficiently moisturized or xerotic (Harding 2004; Rawlings & Harding 2004; Fluhr et al. 2005)....
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...In the SC, water can be found in three types or chemical bonding states: primary water, which is tightly bound to keratin in corneocytes; secondary water, which is hydrogen-bonded around the proteinbound water; and free/bulk water (Rawlings & Harding 2004; Lévêque 2005)....
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...In healthy persons, NMF concentration as well as moisture content decline towards the surface of the skin (Rawlings & Harding 2004)....
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...%) and inorganic ions (20%; Rawlings & Harding 2004)....
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