Estimating the influence of age-related changes in skin stiffness on tactile perception for static stimulations

Abstract

It is difficult to experimentally observe the influence of differences in individual skin properties of human fingers on tactile perceptions. During subjective experiments, many parameters, such as skin properties, the transmittance of nerve signals, and individual feelings are intricately mixed; therefore, it is difficult to identify which elements are affected and to what extent. It has not been determined how age-related changes in the stiffness of skin influence tactile perceptions. We developed a two-dimensional cross-section human fingertip finite element model based on previous studies. Then, we estimated the influence of age-related changes in skin stiffness on Merkel cells and tactile perceptions by using finite element analysis. Age-related changes in skin stiffness were described by changing skin material properties in the model. Simulations using a model involving the fingertip being contacted with a rigid flat plate or a 2-point indenter were performed. Using a rigid flat plate and standard skin material properties, the contact width between the finger pad and the object was 5 mm. Meanwhile, the width changed from 5 mm to 4 mm when using a model of age-related changes of skin. Using a rigid 2-point indenter, the difference in the peak-to-valley of the Mises distribution around the Merkel cells indicated 2-point discrimination. Besides, the difference decreased by approximately 43% with changes in skin stiffness. These results indicated that age-related changes in skin stiffness influenced tactile perceptions.

The stiffness of living tissues and its implications for tissue engineering

“…Parallels could also be drawn between laminated composite materials and organs such as the skin, which is composed of three layers of distinct but interacting tissue (epidermis, dermis and hypodermis). The skin has bulk elastic moduli of up to several hundred kPa 117 whereas the fibre-reinforced dermis 118 has elastic moduli of around 35-150 kPa and the hypodermis has elastic moduli of around 2 kPa, similar to adipose tissue 111,112,119,120 . The lens of the eye comprises a stiff capsule with elastic moduli of 2-3 MPa and a very soft core (0.8-11.8 kPa) [121][122][123][124] .…”

Computational analysis of the relationship between mechanical state and mechanoreceptor responses during scanning of a textured surface

“…We chose to evaluate von Mises stress as a measure of mechanical state based on previous analyses. 3,5,9,10,22 Srinivasan and DandekaR 2 have indicated that SED is relevant to SA-I mechanoreceptor responses. SED can be converted to von Mises stress when dealing with incompressible materials, as in this study.…”

“…Therefore, several researchers have evaluated the mechanical state associated with mechanical stimuli at typical mechanoreceptor locations using finite element (FE) analysis, providing further insight into the mechanisms underlying tactile perception. [2][3][4][5] One previous study revealed that the mechanical state (e.g. strain energy density (SED) and maximum principal strain) at mechanoreceptor locations is correlated with the experimentally measured nerve firing rate (impulse rate) in slowly adapting type I (SA-I) afferent nerve fibers.…”

Changes in emotional state while holding a slimy fluid in the palmar skin

“…Although the humidity and temperature affect the skin friction, the friction generated between the skin and the contacting surface is properly regulated to support activities of daily living and avoid skin injury (Klaassena et al, 2017;Morales-Hurtado et al, 2017;Klaassen et al, 2016;Meredith et al, 2015). The friction generated on the skin surface also provides us with tactile perceptions derived from the mechanoreceptors in each layer of the skin (Hamasaki et al, 2018). The mechanoreceptor is a sensory receptor responding to the mechanical deformation of the skin.…”