<i>In vivo</i> confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment

Dąbrowska, Agnieszka; Adlhart, Christian; Spano, Fabrizio; Rotaru, G.-M.; Derler, S.; Zhai, Lina; Spencer, Nicholas D.

doi:10.1116/1.4962547

Cited by 44 publications

(56 citation statements)

References 56 publications

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“…On the contrary, subject 3 has the most hydrated skin. The water diffusion in the SC is driven by the water concentration gradient in the SC : as the occlusion time increases, the hydration gradient decreases and the water concentration of the surface SC saturates to the hydration level at the bottom of the SC . From the results shown in Table , we find that β 2 and τ 2 in Eq.…”

Section: Resultsmentioning

confidence: 85%

In vivo THz imaging of human skin: Accounting for occlusion effects

Sun

Parrott

et al. 2017

Journal of Biophotonics

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In vivo terahertz (THz) imaging of human skin needs to be done in reflection geometry due to the high attenuation of THz light by water in the skin. To aid the measurement procedure, there is typically an imaging window onto which the patient places the area of interest. The window enables better pulse alignment and helps keep the patient correctly positioned during the measurement. In this paper, we demonstrate how the occlusion caused by the skin contact with the imaging window during the measurement affects the THz response. By studying both rapid point measurements and imaging over an area of a human volar forearm, we find that even 5 seconds of occlusion affects the THz response. As the occlusion time increases, the skin surface water content increases, resulting in the reduction of the amplitude of the reflected THz pulse, especially in the first 3 minutes. Furthermore, it was found that the refractive index of the volar forearm increased by 10% to 15% after 20 minutes of occlusion. In this work, we examine and propose a model for the occlusion effects due to the quartz window with a view to compensating for its influence.

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Section: Resultsmentioning

confidence: 85%

In vivo THz imaging of human skin: Accounting for occlusion effects

Sun

Parrott

et al. 2017

Journal of Biophotonics

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“…Free moisture would be expected to lead to a reduction of the friction. Moreover, taking steps to eliminate the presence of liquid water, the dark regions between (forearm) skin and a transparent window observed in high-resolution Raman microscopy have also indicated the presence of solidsolid junctions (30).…”

Section: Discussionmentioning

confidence: 99%

Why pens have rubbery grips

Dzidek

Bochereau

Johnson

et al. 2017

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

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The process by which human fingers gives rise to stable contacts with smooth, hard objects is surprisingly slow. Using highresolution imaging, we found that, when pressed against glass, the actual contact made by finger pad ridges evolved over time following a first-order kinetics relationship. This evolution was the result of a two-stage coalescence process of microscopic junctions made between the keratin of the stratum corneum of the skin and the glass surface. This process was driven by the secretion of moisture from the sweat glands, since increased hydration in stratum corneum causes it to become softer. Saturation was typically reached within 20 s of loading the contact, regardless of the initial moisture state of the finger and of the normal force applied. Hence, the gross contact area, frequently used as a benchmark quantity in grip and perceptual studies, is a poor reflection of the actual contact mechanics that take place between human fingers and smooth, impermeable surfaces. In contrast, the formation of a steady-state contact area is almost instantaneous if the counter surface is soft relative to keratin in a dry state. It is for this reason that elastomers are commonly used to coat grip surfaces.finger friction | true contact area kinetics | biotribology | fingerprints

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“…The thickness of the epidermis depends on the body site in a similar way . The SC thickness is related to many other phenomena, such as surface morphology, hydration level, and permeability to various substances . Since the SC acts as a barrier layer, penetration through the skin is higher on body sites with thinner SC .…”

Section: Introductionmentioning

confidence: 99%