Wear 263 (2007) 1124–1132 Finger friction: Grip and opening packaging R. Lewis ∗ , C. Menardi, A. Yoxall, J. Langley Department of Mechanical Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom Received 30 July 2006; received in revised form 4 December 2006; accepted 9 December 2006 Available online 21 March 2007 Abstract A great deal of work has been carried out to investigate skin friction, most has been aimed at determining the effect of skin condition and driven by developers of cosmetic products who are interested in the measurement of dynamic coefficient of friction. Little work has been carried out to look at grip and static coefficients of friction. In this work a rig was developed for measuring finger friction and used to determine static coefficient of friction against a number of packaging materials related to bottles and jars. Tests were carried out using bare fingers and two types of glove (nitrile rubber kitchen gloves and latex protective gloves for use in a laboratory, etc.). The gloves were found to increase friction. Tests using wet and oil contaminated conditions indicated that a small amount of water would actually increase friction over the dry case, but a similar amount of oil would reduce it greatly. Analytical calculations using measured friction coefficients and human force data from the literature were used to assess the human torques that could be applied to a sample bottle (closure and bottle body). These were validated by comparison with values from bottle and jar based torque measurement devices. The predicted values were compared with calculated bottle opening torques for a range of age groups (male and female). It was found that elderly females may have difficulties opening the bottle. With some further work to look at effect of contact area and different grips this approach will be a useful design tool to help make packaging more inclusive. © 2007 Elsevier B.V. All rights reserved. Keywords: Finger friction; Grip; Bottle opening 1. Introduction Having good grip is extremely important and forms part of many every day activities, such as holding implements (pens, cutlery, etc.), driving a car (steering wheel and other controls), opening packaging, etc. Although finger friction is therefore a major part of normal life, very little documentation of factors affecting it has occurred. Skin friction generally has been studied extensively (see for example the review paper by Sivamani et al. [1], which details much of the work). This research, has mainly been driven by developers of cosmetic products, such as skin creams, etc., who are more interested in dynamic friction coefficients that can give information on skin health and hydration, rather than the static values needed for grip assessment. The previous studies have ∗ Corresponding author. Tel.: +44 114 2227838; fax: +44 114 2227890. E-mail address: roger.lewis@sheffield.ac.uk (R. Lewis). also has focussed on a whole range of body parts, e.g. arms, backs, hands and thighs, but not often on fingers. Some previous work has however been carried out to inves- tigate grip [2,3]. This has tended to be very application specific and no generic understanding has been developed. Results from the large amount of work orientated towards ergonomics and design of handles, etc. (see for example [4,5]) have mainly been presented in terms of torque and force and little attention has been paid to the actual skin/handle interface. None of the work on grip, however, has been related to the daily activities listed above, it is completely focused on workplace practise. There has been some work recently on feel and material sur- face roughness related to packaging [6], but again no friction data was collected. Feel is clearly important, however, as it is unsat- isfactory being able to grip something, but suffering discomfort at the same time. Many consumers experience some difficulties opening cer- tain types of packaging (this is evidenced by the number of reported accidents after using inappropriate implements to aid 0043-1648/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2006.12.024