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Nowadays there is a wide variety of surgical sutures available in the market. Surgical sutures have different sizes, structures, materials and coatings, whereas they are being used for various surgeries. The frictional performances of surgical sutures have been found to play a vital role in their functionality. The high friction force of surgical sutures in the suturing process may cause inflammation and pain to the person, leading to a longer recovery time, and the second trauma of soft or fragile tissue. Thus, the investigation into the frictional performance of surgical suture is essential. Despite the unquestionable fact, little is actually known on the friction performances of surgical suture-tissue due to the lack of appropriate test equipment. This study presents a new penetration friction apparatus (PFA) that allowed for the evaluation of the friction performances of various surgical needles and sutures during the suturing process, under different contact conditions. It considered the deformation of tissue and can realize the puncture force measurements of surgical needles as well as the friction force of surgical sutures. The developed PFA could accurately evaluate and understand the frictional behaviour of surgical suture-tissue in the simulating clinical conditions. The forces measured by the PFA showed the same trend as that reported in literatures., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In the past decades, skin friction research has focused on determining which variables are important to affect the frictional behaviour of in vivo human skin. Until now, there is still limited knowledge on these variables. This study has used a large dataset to identify the effect of variables on the human skin, subject characteristics and environmental conditions on skin friction. The data are obtained on 50 subjects (34 males and 16 females). Friction measurements represent the friction between in vivo human skin and an aluminium sample, assessed on three anatomical locations. The coefficient of friction increased significantly (p<0.05) with increasing age, increasing ambient temperature and increasing relative air humidity. A significant inversely proportional relationship was found between friction and both the amount of hair present on the skin and the height of the subject. Other outcome variables in this study were the hydration of the skin and the skin temperature., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: The frictional characteristics of skin-object interactions are important when handling objects, in the assessment of perception and comfort of products and materials and in the origins and prevention of skin injuries. In this study, based on statistical methods, a quantitative model is developed that describes the friction behaviour of human skin as a function of the subject characteristics, contact conditions, the properties of the counter material as well as environmental conditions., Aims: Although the frictional behaviour of human skin is a multivariable problem, in literature the variables that are associated with skin friction have been studied using univariable methods. In this work, multivariable models for the static and dynamic coefficients of friction as well as for the hydration of the skin are presented., Materials & Methods: A total of 634 skin-friction measurements were performed using a recently developed tribometer. Using a statistical analysis, previously defined potential influential variables were linked to the static and dynamic coefficient of friction and to the hydration of the skin, resulting in three predictive quantitative models that descibe the friction behaviour and the hydration of human skin respectively., Results and Discussion: Increased dynamic coefficients of friction were obtained from older subjects, on the index finger, with materials with a higher surface energy at higher room temperatures, whereas lower dynamic coefficients of friction were obtained at lower skin temperatures, on the temple with rougher contact materials. The static coefficient of friction increased with higher skin hydration, increasing age, on the index finger, with materials with a higher surface energy and at higher ambient temperatures. The hydration of the skin was associated with the skin temperature, anatomical location, presence of hair on the skin and the relative air humidity., Conclusion: Predictive models have been derived for the static and dynamic coefficient of friction using a multivariable approach. These two coefficients of friction show a strong correlation. Consequently the two multivariable models resemble, with the static coefficient of friction being on average 18% lower than the dynamic coefficient of friction. The multivariable models in this study can be used to describe the data set that was the basis for this study. Care should be taken when generalising these results., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Tactile perception is a complex system, which depends on frictional interactions between skin and counter-body. The contact mechanics of tactile friction is governed by many factors such as the state and properties of skin and counter-body. In order to discover the connection between perception and tactile friction on textured stainless steel sheets, both perception experiments (subjective) and tactile friction measurements (objective) were performed in this research. The perception experiments were carried out by using a panel test method to identify the perceived roughness, perceived stickiness and comfort level from the participants. For the friction experiments, tactile friction was measured by a multi-axis force/torque transducer in vivo. The perceived stickiness was illustrated as an effective subjective stimulus, which has a negative correlation to the comfort perception. No significant evidence was revealed to the connection between the perceived roughness and comfort perception, and this relationship may be influenced by the participants' individual experience, gender and moisture level of skin. Furthermore, the kinetic tactile friction was concluded as an objective stimulus to the comfort perception with a negative correlation. [ABSTRACT FROM AUTHOR]

The lifetime of sheet metal forming (SMF) tools is often limited by galling, a wear type that affects the surface quality of the products and the lifetime of SMF tools. Since SMF tools represent high economical value, it is clear that improvement and prediction of tool life is of high industrial importance. Therefore, models are required that can predict friction and wear related phenomena in SMF-processes, in particular galling. This paper demonstrates the application of a wear model, which is able to predict the initiation of galling in lubricated sheet metal forming processes, to laboratory results gained with the TNO slider-on-sheet tribometer. Experiments are conducted with different (coated) tool surfaces, in sliding contact with stainless steel sheet, using two lubricants. By comparing the critical temperature of the generated boundary layer with the flash temperature at the interface of the sheet and individual tool summits, it is possible to predict whether or not galling initiation will occur. It is shown that the laboratory results are in good agreement with the predicted results of the presented wear model. Galling initiation in lubricated sheet metal forming processes, can be avoided by the application of smooth tool surfaces with enhanced thermal conductivity and lubricants which form boundary layers with a high critical temperature. [Copyright &y& Elsevier]

Abstract: The friction behaviour of the human fingerpad as a function of asperity geometry was investigated experimentally. Surface textures consisting of evenly distributed spherically tipped asperities were used for in vivo testing. Using analytical expressions, a multi-scale model was developed to explain the observed friction behaviour as a function of texture geometry, load and skin properties. Friction is found to increase with increasing tip radius. A minimum value for the coefficient of friction seems to exist as a function of asperity density. A maximum value for tip spacing exists above which the contact is not determined by the texture properties only. According to the model normal adhesion plays an important role in the observed friction behaviour. [Copyright &y& Elsevier]

Abstract: Friction involving human skin plays a key role in human life. The availability of a portable tribometer improves the accessibility to large number of both subjects and anatomical sites. This is the first mobile device suitable to measure skin friction with a controlled and variable normal load (range 0.5–2N) and velocity (range 1–10mm/s) of a material of choice making a sliding rotational movement over the skin. The results of a pilot study, using stainless steel samples on the ventral forearm compare to results in the literature. The new device can be used for more extensive research to found these results and determine the effects of normal load or sliding velocity on the skin''s frictional behaviour. [Copyright &y& Elsevier]

Finger pad friction varies significantly between individuals due to personal differences and environmental effects. For this reason, comparison of the absolute friction values becomes non-informative and is rarely reported in literature. This work investigates whether friction data can be normalised to correlate between individuals. A set of textured samples were tested by 10 volunteers in dry sliding conditions with a range of normal loads up to 4 N. A reference smooth sample was used for each participant to normalise the dataset. The proposed approach allows to eliminate one of the unknown parameters, e.g., finger pad ridge contact area function, and discuss the data with respect to other variables. • Friction measurements from 10 volunteers, 4 samples and 9 normal loads were analysed to propose a normalisation method. • Normalisation reduces one of the personal variables and allows friction comparison between individuals. • Friction measurements normalised by a reference represent a change of contact area fraction with normal load. • Volunteers showed similar fractions of real contact area despite differences in skin properties and friction. [ABSTRACT FROM AUTHOR]

The frictional performance of ex vivo skin was studied in a range of pressures between 0.5 and 20 kPa. Modifications in the coefficient of friction under different conditions stressed the important role of adhesion. The friction coefficient of “untreated” skin was obtained between 2.3–0.5, between 5.5 and 0.65 for wet skin and in a range between 0.65 and 0.35 for oil-covered skin. The contribution of capillary adhesion under wet conditions was analysed by the Hertzian and JKR contact models. The high coefficient of friction obtained under wet conditions could not be explained by the softening effect of the stratum corneum and capillary adhesion only. The results suggested a further influence of water in the physicochemical properties of the stratum corneum with a subsequent effect on friction. [ABSTRACT FROM AUTHOR]

This research aims to analyse the interaction of three artificial skin equivalents and human skin against the main material components of artificial turf. The tribological performance of Lorica, Silicone Skin L7350 and a recently developed Epidermal Skin Equivalent (ESE) were studied and compared to ex-vivo human skin samples. The surface of the ex-vivo skin was analysed via confocal microscopy and histology. The results indicated a similar performance of the Lorica and ESE samples when compared to the ex-vivo skin whereas the Silicone Skin L7350 showed significant differences. The results suggested also a key role of the intrinsic properties of the NBR material to the friction against human skin, compared to PA 6.6 or PE surfaces in a similar sliding contact. [ABSTRACT FROM AUTHOR]

Abstract: The main obstacle to calculate the ‘feel’ of a product from its surface properties is the ill-defined surface topography that is encountered after the most surface finishing processes. In this work this obstacle was avoided by producing well-defined surface topographies by laser texturing. The friction of textures having surface features with varying radii and spacings was investigated by measuring friction against the fingerpad. Within the range of conditions tested the coefficient of friction decreased with increasing normal load. The relation between the surface texture parameters and the coefficient of friction is influenced by the scale-dependent elastic behaviour of the skin top layer. [Copyright &y& Elsevier]