Finger friction: Grip and opening packaging

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.