Frictional behaviour of running sock textiles against plantar skin

Friction blisters on feet are a common dermatological injury among long-distance runners which can result from repeated shearing of the skin. Previous studies have shown that an increase in moisture level between the sock - skin interface tends to increase the friction and hence the likelihood of blister formation. For the past few decades, many new sock technologies have been developed based on the principle of friction reduction to prevent blisters such as ‘friction-free’ and double layer running socks. However, there have been very few published results on their frictional performance. Five different running sock materials were selected based on the variations of their knit pattern and fibre composition. The frictional behaviour of these sock materials against whole plantar skin was then assessed in dry condition. All tests were conducted using a bespoke rig that was developed at the University of Sheffield for studies on foot friction. 26 subjects were recruited for this purpose and friction was measured for a range of normal loads. Subjects’ feet were kept at their natural level of hydration, monitored at specific intervals using the Corneometer® CM 825 device. It was observed that there was a positive correlation (p<0.05) between foot hydration and friction force. However, no particular trend can be seen in the friction coefficient values between the tested sock types. This suggests that the properties of the subject's foot had more prominent effect on the friction levels than the knit pattern and composition of sock materials under dry contact conditions. Outcomes from this study indicate that the natural variations in the plantar skin and level of moisture present had a more substantial impact on friction behaviour than any changes in knit pattern or sock material, suggesting the control of moisture levels within the shoe environment is a key factor of concern

Influence of medical gloves on fingerpad friction and feel

Friction experiments were carried out sliding a fingerpad, in both a bare state and with a latex glove donned, across a force plate to determine friction levels for different contact surface conditions (dry/wet; steel/glass). Donning a glove was found to increase the friction in dry conditions, but reduce it in wet conditions. A range of vibration frequencies were found to occur during sliding and the pronounced stick-slip behaviour for a bare finger sliding on wet glass was not found to occur when a latex glove was donned. These frequencies, along with those measured in a previous study, were used to inform the design of a tactile vibration perception study utilising a vibrating platform to replicate the sensation of finger sliding. The use of gloves was found to reduce the amplitude threshold at which participants were able to perceive vibrations. This effect was more extreme for double glove use, compared to single glove use. Glove donning also reduced the ability of participants to perceive differences in the frequency of vibrations. These findings have implications for surgeons' ability to carry out tactile explorations and the protocol described in this paper can be used for future studies on the effect of glove use on feel

Radiofrequency Heating of the Cornea: An Engineering Review of Electrodes and Applicators

This paper reviews the different applicators and electrodes employed to create localized heating in the cornea by means of the application of radiofrequency (RF) currents. Thermokeratoplasty (TKP) is probably the best known of these techniques and is based on the principle that heating corneal tissue (particularly the central part of the corneal tissue, i.e. the central stroma) causes collagen to shrink, and hence changes the corneal curvature. Firstly, we point out that TKP techniques are a complex challenge from the engineering point of view, due to the fact that it is necessary to create very localized heating in a precise location (central stroma), within a narrow temperature range (from 58 to 76ºC). Secondly, we describe the different applicator designs (i.e. RF electrodes) proposed and tested to date. This review is planned from a technical point of view, i.e. the technical developments are classified and described taking into consideration technical criteria, such as energy delivery mode (monopolar versus bipolar), thermal conditions (dry versus cooled electrodes), lesion pattern (focal versus circular lesions), and application placement (surface versus intrastromal)

Skin tribology: Science friction?

The application of tribological knowledge is not just restricted to optimizing mechanical and chemical engineering problems. In fact, effective solutions to friction and wear related questions can be found in our everyday life. An important part is related to skin tribology, as the human skin is frequently one of the interacting surfaces in relative motion. People seem to solve these problems related to skin friction based upon a trial-and-error strategy and based upon on our sense for touch. The question of course rises whether or not a trained tribologist would make different choices based upon a science based strategy? In other words: Is skin friction part of the larger knowledge base that has been generated during the last decades by tribology research groups and which could be referred to as Science Friction? This paper discusses the specific nature of tribological systems that include the human skin and argues that the living nature of skin limits the use of conventional methods. Skin tribology requires in vivo, subject and anatomical location specific test methods. Current predictive friction models can only partially be applied to predict in vivo skin friction. The reason for this is found in limited understanding of the contact mechanics at the asperity level of product-skin interactions. A recently developed model gives the building blocks for enhanced understanding of friction at the micro scale. Only largely simplified power law based equations are currently available as general engineering tools. Finally, the need for friction control is illustrated by elaborating on the role of skin friction on discomfort and comfort. Surface texturing and polymer brush coatings are promising directions as they provide way and means to tailor friction in sliding contacts without the need of major changes to the produc

The effect of topical anti blister products on the risk of friction blister formation on the foot

Introduction Foot blisters are a common injury, which can impact on activity and lead to infection. Increased skin surface hydration has been identified as a risk factor for blister formation, indicating that a reduction in hydration could reduce the risk of blister formation. Method Thirty healthy adults were randomised into 3 groups, each receiving a preventative foot blister treatment (2Toms® Blister Shield®; Flexitol® Blistop and Boots Anti–Perspirant Foot Spray). Cycles of compression and shear loads where applied to heel skin using a mechanism driven by compressed air. Temperature changes were measured during load application using a thermal imaging camera (FLIR Systems Inc. and Therm CAM™ Quick Report). Near surface hydration of the skin was measured using a Corneometer® (C & K, Germany). Results There was no significant difference in the rate of temperature change of the skin between the three groups compared to not using products (p = 0.767, p = 0.767, p = 0.515) or when comparing each product (p = 0.551). There was a significant decrease in near surface skin hydration, compared to baseline, after the application of powder (−8.53 AU, p = 0.01). There was no significant difference in hydration after the application of film former and antiperspirant (−1.47 AU, p = 0.26; −1.00 AU, p = 0.80, respectively). Conclusion With the application of external load we found no significant difference in the effect of the three products on temperature change. The powder product demonstrated an effect on reducing the risk of blister. It is postulated that powder may have a barrier effect