Álvarez-Asencio Rubén, Wallqvist Viveca, Kjellin Mikael, Rutland Mark W, Camacho Alejandra, Nordgren Niklas, Luengo Gustavo S
KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, SE-100 44 Stockholm, Sweden; Institute for Advanced Studies, IMDEA Nanoscience, c/Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain.
SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden.
J Mech Behav Biomed Mater. 2016 Feb;54:185-93. doi: 10.1016/j.jmbbm.2015.09.014. Epub 2015 Sep 21.
The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young׳s modulus of the stratum corneum varied over the surface with a mean value of about 0.4GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4µN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.
利用原子力显微镜在不同长度尺度下评估了皮肤最外层角质层对变形的机械阻力。首先使用尖锐的硅探针进行纳米力学表面测绘，结果显示角质层的杨氏模量在表面上存在变化，平均值约为0.4吉帕。力压痕测量表明，仅在高加载力（超过4微牛）下皮肤表面才会出现永久变形。使用纳米力学成像进一步证明了后一种效应，其中获得的深度剖面图清楚地说明了法向力增加对弹性/塑性表面变形的影响。利用单根毛发纤维探针进行的力测量支持了角质层在纳米尺度上具有高弹性的纳米压痕结果，但揭示了变形的横向尺度决定了有效弹性模量。这一结果解决了文献报道值差异很大的问题，并将有助于理解在生长过程中向后卷曲并与皮肤相互作用的剃须毛发相互作用的生物物理学。
