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Microindentation and nanoindentation of human fingernails at varying relative humidity

Published online by Cambridge University Press:  31 January 2011

Laura Farran ,
A. Roland Ennos  and
Stephen J. Eichhorn
Laura Farran
Affiliation:
Materials Science Centre, School of Materials, University of Manchester, M1 7HS, United Kingdom
A. Roland Ennos
Affiliation:
Faculty of Life Sciences, University of Manchester, Manchester, M1, 3NJ, United Kingdom
Stephen J. Eichhorn*
Affiliation:
Materials Science Centre, School of Materials, University of Manchester, M1 7HS, United Kingdom
*
a) Address all correspondence to this author. e-mail: s.j.eichhorn@manchester.ac.uk
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Abstract

The indentation properties of human fingernails at varying humidity are reported. The samples were indented using both microindentation, to obtain their Vickers hardness and also nanoindented using a Berkovich indenter tip. The relative humidity (RH) of the samples was controlled by using salt solutions with a sealed and enclosed environment surrounding the testing equipment. It was shown that the Vickers hardness of the samples is sensitive to RH, with recovery of the nail material more readily occurring for nails tested at >55% RH. This recovery mechanism is discussed in terms of the structure of the nails, and this approach is also suggested as a technique for following recovery mechanisms in natural materials under varying humidity. The hardness obtained by nanoindentation is similar to previously published data, but does not change with humidity. The modulus of the nails is also insensitive to relative humidity, but in the same range as the value derived from the microindentation tests.

Keywords

BiologicalNanoindentationStress/strain relationship
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 3 , March 2009 , pp. 980 - 984
Copyright
Copyright © Materials Research Society 2009

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