title: Nanomechanical properties of human skin and introduction of a novel hair indenter.
abstract: 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.
authors.affiliation: 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.
authors.forename: Rubén
authors.initials: R
authors.lastname: Álvarez-Asencio
authors.affiliation: SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden.
authors.forename: Viveca
authors.initials: V
authors.lastname: Wallqvist
authors.affiliation: SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Kjellin
authors.affiliation: KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, SE-100 44 Stockholm, Sweden; SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Rutland
authors.affiliation: L'Oréal Research and Innovation, Chicago, USA.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Camacho
authors.affiliation: SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden. Electronic address: niklas.nordgren@sp.se.
authors.forename: Niklas
authors.initials: N
authors.lastname: Nordgren
authors.affiliation: L'Oréal Research and Innovation, Aulnay-Sous-Bois, France. Electronic address: gluengo@rd.loreal.com.
authors.forename: Gustavo S
authors.initials: GS
authors.lastname: Luengo
mesh_terms: D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D004817:Epidermis; D006801:Humans; D008422:Materials Testing / Q000295:instrumentation*; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D036103:Nanotechnology / Q000295:instrumentation*; D012825:Silicon
chemical_list: D012825:Silicon
keywords: Atomic Force Microscopy; Hair; Mechanical properties; Stratum corneum