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Towards simultaneous measurements of skin friction and contact area: Results and experiences
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).ORCID iD: 0000-0003-2489-0688
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2015 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 229, no 3, 230-242 p.Article in journal (Refereed) Published
Abstract [en]

This article investigates one of the important parameters when designing for feel, namely the friction coefficient. An experiment was performed to evaluate how fringe projection could be used to investigate the topography of the fingertip, especially while in contact and sliding on a smooth surface. By allowing this smooth surface to be a small sheet of glass, a topographic camera could take pictures through it. The glass was also connected to a universal force gauge to measure normal and tangential forces from which the coefficient of friction could be calculated. The intention was to get dependable data on the forces, coefficient of friction, apparent contact area and actual contact area. This set-up was tested using 66 students who used one and three fingers in both dry and wet conditions and with a rubber glove. In order to measure natural everyday friction, they were not given any particular instructions on how to clean or slide their fingers. This method resulted in a much higher variation in friction coefficients than has been found in previous research. In particular, many higher values were noticed. This illustrates that the friction coefficient is a very hard parameter to rely on when it comes to designing surfaces for feel.

Place, publisher, year, edition, pages
Sage Publications, 2015. Vol. 229, no 3, 230-242 p.
Keyword [en]
Biotribology, finger, tactility, adhesion, friction test methods, water, glass
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-162947DOI: 10.1177/1350650114521798ISI: 000349985500002ScopusID: 2-s2.0-84923361088OAI: diva2:800191

QC 20160413

Available from: 2015-04-02 Created: 2015-03-26 Last updated: 2016-05-09Bibliographically approved
In thesis
1. Adhesion and Friction - a Study on Tactility
Open this publication in new window or tab >>Adhesion and Friction - a Study on Tactility
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although we are surrounded by hundreds of surfaces we can still distinguish them from each other simply by touch. The tactile information, interpreted by our brain and given by our fingers, is precise, but to put words to the sensation is very difficult — is it smooth, sticky or harsh? We do not only perceive surfaces differently, we also describe them in our own way. Luckily the forces and deformations that the skin are exposed to when sliding over a surface is ruled by laws of nature.

This thesis investigates the contact between finger and surface and how it is affected by, for example, material properties, surface texturing or changes in climate. By measuring contact area, friction coefficient, and adhesion, using different materials and under different conditions, conclusions could be drawn. Also, a model for the contact between a finger and a sinus­oidal surface was developed, which could be used to estimate contact area, deformation and resulting friction coefficient.

Results showed how differences in for example material, surface topography and environ­ment affect the interaction between finger and surface, and what consequences it has. If the objective is to change the feel of a surface or to alter the grip, this thesis could work as a support.

Paper A investigates the area and friction between finger and glass surface under different conditions.

Paper B presents a model for the contact area and deformation for a finger in contact with a sinusoidal surface.

Paper C is a validation of the contact area model. Here it was used on new surfaces and compared with new finger friction measurements.

Paper D mainly examines whether the adhesion or stickiness of different surfaces is distinguishable by a test panel and how this affects the perceived pleasantness of the surface.

Paper E relates to the adhesion and friction for a bioskin probe and skin. Tests were made to evaluate how an artificial probe can be used to evaluate the tactile properties of a surface.

Abstract [sv]

Även om vi omges av hundratals olika ytor kan vi fortfarande skilja dem åt med hjälp av känseln. Den taktila informationen från fingertopparna som tolkas av hjärnan är precis, men att sätta ord på hur ytan känns är väldigt svårt. Len, sträv eller grov? Vi upplever inte bara ytorna olika utan beskriver dem också på olika sätt. Krafterna och deformationerna som huden utsätts för när den glider över en yta styrs dock av naturlagar.

Denna avhandling utreder kontakten mellan fingertopp och yta och hur den påverkas av exempelvis materialval, ytstruktur eller förändringar i klimat. Genom mäta kontaktarea, friktionskoefficient och adhesion för olika material i varierande omgivning kunde slutsatser dras. En modell för kontakten mellan fingertopp och sinusformad yta togs fram vilken kunde användas till att uppskatta kontaktarea, deformation och resulterande friktionskoefficient.

Resultaten visade hur skillnader i exempelvis material, yttopografi och omgivning påverkar kontakten mellan finger och yta och vilka kon­sekvenser detta får. Om målet är att förändra känslan eller friktionen för en yta kan denna avhandling fungera som stöd.

Artikel A undersöker kontakten och friktionen mellan fingertopp och glasyta för olika förhållanden.

Artikel B presenterar en modell för arean och deformationen som sker för fingertopp och sinusformad yta i kontakt.

Artikel C är en validering av modellen. Här användes den för nya ytor och jämfördes med nya mätningar av fingerfriktion.

Artikel D undersöker i huvudsak huruvida en testpanel kan särskilja adhesionen för olika ytor och hur detta påverkar hur den känns.

Artikel E arbetar vidare med adhesion och undersöker och hur en testkropp av artificiell hud kan användas för adhesionsmätningar av en yta. Detta för att med relativt enkla mätningar kunna uppskatta ytans taktila egenskaper.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xii, 42 p.
TRITA-MMK, ISSN 1400-1179 ; 2016:03
Adhesion, finger, friction, humidity, material, model, tactile friction, tactility
National Category
Mechanical Engineering
Research subject
Machine Design
urn:nbn:se:kth:diva-186208 (URN)978-91-7595-955-9 (ISBN)
Public defence
2016-05-27, F3, Lindstedtsvägen 26, KTH Campus, Stockholm, 14:00 (English)

QC 20160504

Available from: 2016-05-09 Created: 2016-05-04 Last updated: 2016-05-09Bibliographically approved

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Duvefelt, Kenneth B. K.Olofsson, Ulf L-OJohannesson, Carl Michael J.
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