Role of occlusion in non-coulombic slip of the finger pad

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Authors

  • Simon Johnson
  • Séréna Bochereau
  • Vincent Hayward

Colleges, School and Institutes

External organisations

  • University of Birmingham, School of Chemical Engineering
  • Sorbonne Universités, UPMC Univ Paris 06, CNRS
  • Unilever R and D Port Sunlight

Abstract

Understanding how fingers slip on surfaces is essential for elucidating the mechanisms of haptic perception. This paper describes an investigation of the relationship between occlusion and the non-Coulombic slip of the finger pad, which results in the frictional force being a power law function of the normal load, with an index n; Coulombic slip corresponds to n = 1. For smooth impermeable surfaces, occlusion of moisture excreted by the sweat glands may cause up to an order of magnitude increase in the coefficient of friction with a characteristic time of ~ 20 s. This arises because the moisture plasticises the asperities on the finger print ridges resulting in an increase in their compliance and hence an increase in the contact area. Under such steady state sliding conditions a finger pad behaves like a Hertzian contact decorated with the valleys between the finger print ridges, which only act to reduce the true but not the nominal contact area. In the limit, at long occlusion times (~ 50 s), it can be shown that the power law index tends to a value in the range 2/3 ≤ n ≤ 1. In contrast, measurements against a rough surface demonstrate that the friction is not affected by occlusion and that a finger pad exhibits Coulombic slip.

Details

Original languageEnglish
Title of host publicationLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Publication statusPublished - 2014
Event9th International Conference on Haptics: Neuroscience, Devices, Modeling, and Applications, EuroHaptics 2014 - Versailles, France
Duration: 24 Jun 201426 Jun 2014

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume8618
ISSN (Print)03029743
ISSN (Electronic)16113349

Conference

Conference9th International Conference on Haptics: Neuroscience, Devices, Modeling, and Applications, EuroHaptics 2014
CountryFrance
CityVersailles
Period24/06/1426/06/14

Keywords

  • Coulombic slip, Finger pad, Friction, Occlusion, Skin hydration