In vivo model of the mechanical properties of the human skin under suction

Abstract

BACKGROUND/AIMS: A new method for the in vivo characterization of the mechanical properties of skin has been developed. This comprises a suction chamber and an ultrasound device to measure both the vertical displacement of the skin's surface, and the skin's thickness. METHODS: A mathematical model of the mechanical behaviour of a taught elastic membrane is used to obtain a set of parameters intrinsic to the skin, such as Young's modulus (E) and the initial stress (sigma0), which reflect the stiffness and the natural tension of the skin, respectively. We also calculated an index of non-elasticity of the skin (unrestored energy ratio, UER), which takes into account the volume of tissue mobilized. It determines a ratio between the energy input to the skin and the energy it dissipates. These parameters were evaluated from the volar forearm of 10 normal male volunteers. RESULTS: The results were: 129+/-88 kPa for E, 13.5+/-5 kPa for sigma0, and 0.42+/-0.04 for UER; with reproducibilities of 9.5%, 12.4% and 6.4%, respectively. CONCLUSIONS: This new suction device was found useful for the study of the behaviour of the skin, and the device may be used for the evaluation of certain skin diseases and their therapy.

An elastic second skin

“…Plots of the instantaneous viscosity as a function of the shear rate illustrated a stronger shear-thinning effect of the Step 1 formulation containing the lead RPB, compared to the lead RPB alone, with a 2-to 3-fold decrease in the instantaneous viscosity at shear rates above 5 sec -1 ( Figure 8 in Supplementary Information). Note that maximum shear rates from 10 4 to 10 5 sec -1 have been reported for the application of topical cream products on skin 28 . The rheological behaviour of Step 1 allows the emulsion to exhibit lower viscosities at the high shear rates associated with topical formulation application, despite the comparable viscosities of 1,500 Pa.s (Step 1 containing the lead RPB) and 1,800 Pa.s (the lead RPB alone) measured at low shear rate of 0.15 sec -1 .…”

“…This test procedure enables the measurement of bulk skin retraction properties, a clinical indicator of skin mechanical function akin to the dermatologic skin tenting test. The negative pressure detected in the suction chamber scales with the skin distensibility, and the retraction times provide an indication of skin elasticity 27,28 . Figure 4a shows a representative skin distensibility plot over 5 consecutive cycles of vacuum application to a representative untreated skin site at baseline.…”

Adhesive properties: a critical issue in transdermal patch development

“…The stress distribution on skin deformation was measured in vivo by tension, torsion, suction and indentation tests [66][67][68][69]. These data were recently used to elaborate skin models for adhesion test, which kept into account the skin deformability [22,[70][71][72] and rugosity [73,74].…”

Mechanical characterization of the rat and mice skin tissues using histostructural and uniaxial data

“…7,12 The mechanical properties of the skin tissue so far have been measured by applying deformation forces, including traction, tension, suction, torsion or indentation in various ways to the skin samples. 11,13,14 Uniaxial extension setups are beneficial as the can be used to evaluate in-plane directional differences in material properties and can be non-invasive, applicable and easy to use in vivo. 15 Characterization of the mechanical properties of murine (rat or mice) skin would be important to allow its use as an animal model for human skin diseases.…”