Understanding the tribological interactions between plantar skin and sock textiles through the development of biofidelic test-beds

Foot friction blisters are one of the most common dermatological injuries experienced by those actively involved in outdoor physical pursuits. The frictional interaction between the human skin and textile fabric is acknowledged as being an important aspect in blister development. Despite growing research in this area, relatively little is known about the friction interaction between plantar skin and textiles. The ultimate aim of this thesis is to achieve enhanced understanding of the complex tribological interactions between human plantar skin and sock textiles. The first part of this thesis primarily focusses on experimental studies conducted on the sock-insole and skin-sock interfaces. Due to the lack of existing standard testing protocols, novel testing protocols were developed and used as a standard testing procedure throughout the experimental studies. The friction study on the entire plantar region was conducted in dry textile conditions whereas the friction study on the plantar aspect of the first metatarsal head (1MTH) was carried out in three significantly different moisture conditions (dry, low moisture and wet). Findings gained from a friction study on the 1MTH region of the foot were then used for validations in the second half of this thesis which concerns the development of a range of prototype biofidelic test-beds to mimic the frictional behaviour of 1MTH region. A set of prototype biofidelic test-beds were developed after considering the appropriate geometry, materials and manufacturing processes. Each test-bed is a two-layer polymer-based physical skin model, with the outer layer representing the epidermal dermal tissue and the inner layer representing the dermal subcutaneous tissues. A steel hemisphere was also embedded within the test-bed to simulate the 1MTH bone. Nine test-beds of differing inner Young’s modulus were made with four of them having texture on their surface layer, obtained from a mould of an actual human foot. All test-beds were subjected to deformation and friction tests in order to validate their performances in the respective aspects, when compared with data obtained from human testing. It is hoped that the understanding gained from the study will close the gaps in the existing knowledge of plantar skin – sock textile friction which can be applied into future foot friction blister studies.