Contact modelling of human skin: What value to use for the modulus of elasticity?

Kuilenburg, Julien van; Masen, Marc Arthur; Heide, Emile van der

doi:10.1177/1350650112463307

Cited by 114 publications

(121 citation statements)

References 39 publications

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“…In contrast, based on a fully elastic approximation combined with a GreenwoodWilliamson-like statistical approach, Masen [50] estimated h to range between −0.66 and −1. However, this latter estimate is an over-simplification because the mechanical properties of skin vary with the size of the contact [39], and a deterministic approach to account for the effects of surface roughness seems more appropriate. For surfaces with a roughness Rq in the order of micrometres and more, the adhesive model gives rather low coefficients of friction, and such low values are not obtained in experiments.…”

Section: Changing Friction By Surface Texturementioning

confidence: 99%

Skin tribology: Science friction?

2013

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Abstract:The application of tribological knowledge is not just restricted to optimizing mechanical and chemical engineering problems. In fact, effective solutions to friction and wear related questions can be found in our everyday life. An important part is related to skin tribology, as the human skin is frequently one of the interacting surfaces in relative motion. People seem to solve these problems related to skin friction based upon a trial-anderror strategy and based upon on our sense for touch. The question of course rises whether or not a trained tribologist would make different choices based upon a science based strategy? In other words: Is skin friction part of the larger knowledge base that has been generated during the last decades by tribology research groups and which could be referred to as Science Friction? This paper discusses the specific nature of tribological systems that include the human skin and argues that the living nature of skin limits the use of conventional methods. Skin tribology requires in vivo, subject and anatomical location specific test methods. Current predictive friction models can only partially be applied to predict in vivo skin friction. The reason for this is found in limited understanding of the contact mechanics at the asperity level of product-skin interactions. A recently developed model gives the building blocks for enhanced understanding of friction at the micro scale. Only largely simplified power law based equations are currently available as general engineering tools. Finally, the need for friction control is illustrated by elaborating on the role of skin friction on discomfort and comfort. Surface texturing and polymer brush coatings are promising directions as they provide way and means to tailor friction in sliding contacts without the need of major changes to the product.Keywords: friction; bio-tribology; skin; soft tissue; surface texture; brush coatings Skin friction in daily lifeThe application of tribological knowledge, i.e., knowledge on the science and technology of interacting surfaces in relative motion, is not restricted to optimizing mechanical and chemical engineering problems. In fact, effective solutions to tribology related questions are evident in our everyday life, as illustrated in fascinating examples described by D. Dowson's "A tribological day" [1]. An important part of the effective solutions in daily life situations is related to skin tribology, as the human skin is frequently one of the interacting surfaces in relative motion. These questions are typically related to optimizing friction and lubrication problems in skin-product interactions, rather than to optimising wear. Take for example the swimming pool or bathroom where material selection and application of anti-slip coatings prevent us from falling when the floor gets wet. Yet, if such coatings do not sufficiently increase friction, one will optimize the tribological system, e.g., by pressing our full foot to the floor and subsequently increasing the true area of contact or by chan...

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Section: Changing Friction By Surface Texturementioning

confidence: 99%

Skin tribology: Science friction?

2013

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“…The skin of the fingers and palm is known to have complex, nonlinear mechanics (61)(62)(63), with properties that vary widely over different spatial and temporal scales (64,65). Modeling the precise skin deformation resulting from a given stimulus requires advanced models (66,67), measurements of individual skin properties (68), many parameters, and considerable computing power.…”

Section: Methodsmentioning

confidence: 99%

Simulating tactile signals from the whole hand with millisecond precision

Saal

Delhaye

Rayhaun

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

226

251

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When we grasp and manipulate an object, populations of tactile nerve fibers become activated and convey information about the shape, size, and texture of the object and its motion across the skin. The response properties of tactile fibers have been extensively characterized in single-unit recordings, yielding important insights into how individual fibers encode tactile information. A recurring finding in this extensive body of work is that stimulus information is distributed over many fibers. However, our understanding of population-level representations remains primitive. To fill this gap, we have developed a model to simulate the responses of all tactile fibers innervating the glabrous skin of the hand to any spatiotemporal stimulus applied to the skin. The model first reconstructs the stresses experienced by mechanoreceptors when the skin is deformed and then simulates the spiking response that would be produced in the nerve fiber innervating that receptor. By simulating skin deformations across the palmar surface of the hand and tiling it with receptors at their known densities, we reconstruct the responses of entire populations of nerve fibers. We show that the simulated responses closely match their measured counterparts, down to the precise timing of the evoked spikes, across a wide variety of experimental conditions sampled from the literature. We then conduct three virtual experiments to illustrate how the simulation can provide powerful insights into population coding in touch. Finally, we discuss how the model provides a means to establish naturalistic artificial touch in bionic hands.mechanoreceptor | tactile afferent | somatosensory periphery | skin mechanics | computational model T he human hand is endowed with thousands of mechanoreceptors of different types distributed across the skin, each innervated by one or more large myelinated nerve fibers (1). These fibers convey detailed information about contact events and provide us with an exquisite sensitivity to the form and surface properties of grasped objects (2, 3). During object manipulation and tactile exploration, the glabrous skin of the hand undergoes complex spatiotemporal mechanical deformations, which in turn, drive very precise spiking responses in individual afferents. Coarse object features, such as edges and corners, are reflected in spatial patterns of activation in slowly adapting type I (SA1) and rapidly adapting (RA) fibers, which are densely packed in the fingertip (3, 4). At the same time, interactions with objects and surfaces elicit high-frequency, low-amplitude surface waves that propagate across the skin of the finger and palm and excite vibration-sensitive Pacinian (PC) afferents all over the hand (5-8).Recording the activity of tactile nerve fibers in monkeys or humans is technically difficult, is slow, and generally yields responses from a single unit at a time (9, 10). Although such recordings have yielded powerful insights into the neural basis of touch, they provide a limited window into the information that the hand c...

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“…MPa depending on the hydration state [43]. On this basis, a hypothesis for the much higher average CoF of the synthetic skin compared to human skin is that the real area of contact at the interface is greater due to a lower effective elastic modulus than the SC on human skin.…”

Section: Effect Of Dry or Moist Skin Conditionsmentioning

confidence: 99%

“…The synthetic skin does not have the complexity of human skin, for which the SC has a thickness in the range 10 to 40 µm and the viable epidermis, dermis and hypodermis layers are of varying thicknesses and have different mechanical properties [43]. It is also unlikely to have an organic surface layer equivalent to that on human skin.…”

Section: Effect Of Dry or Moist Skin Conditionsmentioning

confidence: 99%

Comparison of the Friction Behavior of Occluded Human Skin and Synthetic Skin in Dry and Moist Conditions

Franklin

Baranowska

Hendriks

et al. 2016

Tribology Transactions

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The goal of this work was to assess the suitability of a commercial synthetic skin to simulate occluded human skin friction behaviour in dry and moist skin conditions and under different applied surface pressures, with the view to using this material as a tribological test-bed for healthcare and personal care devices that are in direct contact with the skin during use. A flat rotating ring friction measurement device, in which one part of the skin surface is continuously covered (i.e. occluded), was used to compare the friction behaviour of human skin and the synthetic skin in controlled nominally dry and nominally moist skin conditions. Three loading levels were tested, simulating light, medium and high skin pressures typical of many lifestyleand personal health-related applications. The results showed that the friction behaviour of the synthetic skin tested here was notably different to that of human skin in vivo in terms of the effects of skin hydration, sliding time and applied surface pressure. It is concluded that, for use as a tribological test-bed, the tested synthetic skin model does not provide an acceptable alternative to in vivo tests using human skin.

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Contact modelling of human skin: What value to use for the modulus of elasticity?

Cited by 114 publications

References 39 publications

Skin tribology: Science friction?

Skin tribology: Science friction?

Simulating tactile signals from the whole hand with millisecond precision

Comparison of the Friction Behavior of Occluded Human Skin and Synthetic Skin in Dry and Moist Conditions

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