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

ANALISIS PELAKSANAAN PROMOSI JABATAN STRUKTURAL PADA KANTOR SEKRETARIAT DEWAN PERWAKILAN RAKYAT DAERAH (DPRD) PROVINSI BENGKULU

Tujuan dari pelaksanaan promosi jabatan struktural Pegawai Negeri Sipil adalah untuk memberikan pengakuan jabatan dan imbalan jasa yang semakin besar kepada Pegawai Negeri Sipil. Pelaksanaan promosi jabatan struktural pada sekretariat dewan perwakilan rakyat daerah provinsi Bengkulu mengacu pada peraturan pemerintah Nomor 13 tahun 2002 Tentang Pengangkatan Pegawai Negeri Sipil Dalam Jabatan Struktural. Berkenaan dengan itu, Sekretariat Dewan Perwakilan Rakyat Daerah Provinsi Bengkulu melaksanaan promosi jabatan struktural. Masalah yang dihadapi pada pelaksanaan promosi jabatan adalah tidak sesuai dengan syarat- syarat promosi jabatan struktural yang telah ditetapkan, yang mana syarat umum tersebut adalah pendidikan, jenjang pangkat, prestasi kerja dan kompetensi Pegawai negeri Sipil, sehingga aspek yang digunakan dalam penelitian ini adalah pendidikan, jenjang pangkat, prestasi kerja dan kompetensi, dari aspek tersebut maka informan yang terpilih dalam penelitian ini terdiri dari 5 orang yaitu Mewakili Badan Pertimbangan Jabatan dan Kepangkatan (Baperjakat), Kepala Bagian Umum dan Kepala Sub Bagian Tata Usaha Sekretariat Dewan Perwakilan Daerah Provinsi Bengkulu, serta Sekretaris Dewan Perwakilan Rakyat Daerah Provinsi Bengkulu, sedangkan responden terdiri dari 7 orang yaitu Pegawai Negeri Sipil yang diusulkan promosi dan yang mendapat promosi jabatan tahun 2008. Penelitian ini menggunakan jenis penelitian deskriptif dengan didukung data kualitatif, teknik pengumpulan data dengan observasi, wawancara dan dokumentasi, data yang diperoleh kemudian dianalisis dengan metode analisis deskriptif yang dilakukan dengan menyederhanakan data yang diperoleh dalam bentuk yang mudah dibaca, dipahami, dan diinterprestasikan dimana hal itu dilakukan dalam upaya mencari jawaban atas permasalahan yang ada. Dari hasil penelitian maka dapat diketahui bahwa pelaksanaan promosi jabatan struktural Pegawai Negeri Sipil Pada Sekretariat Dewan Perwakilan Rakyat Daerah Provinsi Bengkulu dinilai telah objektif karena sudah mengacu pada pendidikan, jenjang pangkat, prestasi kerja dan kompetensi Pegawai Negeri Sipil sesuai dengan Peraturan Pemerintah Nomor 13 Tahun 2002

Frictional Behaviour of Running Sock Textiles Against Plantar Skin

AbstractFriction 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

Investigating Foot-sock Friction: A Comparison of Two Different Methodologies

AbstractTwo different methodologies for assessing the friction between plantar skin and sock textiles are compared in this study. The first approach uses a custom-built friction plate rig. The rig consists of sock material mounted on a test plate attached to two load cells that measure normal and shear loads at the skin-sock textile interface. With this methodology, participants are required to slide their foot over the test plate whilst maintaining a targeted normal load and a relatively consistent sliding speed. The second approach uses a pneumatically-driven foot probe loading device. The device includes an instrumented probe with sock material on its contact surface. Participants are instructed to stand on a platform whilst the probe is applied to, and then driven across, the plantar aspect of foot. The cyclic motion of the probe is displacement-controlled and normal and shear loads are measured using load cells. Both approaches allow friction coefficients to be calculated from load data collected during the sliding phase of movement. Data from both approaches was examined, collected from friction tests using the same six participants and sliding contact between the first metatarsal head (1MTH) region and textiles from two commercially available running socks. Both approaches were capable of measuring the friction between 1MTH skin and sock materials and good agreement was found between them. In the dry conditions tested, the cotton-rich sock was found to provide lower friction that the anti-blister sock material

Frictional Interaction between Running Sock Fabrics and Plantar Aspect of First Metatarsal Head in Different Moisture Conditions

AbstractIn a pursuit to further improve the understanding of the factors influencing friction blister formation, friction between running sock textiles and the skin at the first metatarsal head (1MTH) region was investigated in three different moisture conditions (dry, low moisture and wet).Twenty-six participants were recruited and two running sock types were selected based on the variations of their fibre composition and knit structure: 1) a predominantly nylon anti-blister sock and 2) a cotton-rich sock. All friction tests were conducted in controlled room conditions with a temperature of between 20 to 22°C and a relative humidity of 40 to 60% using a bespoke rig developed at the University of Sheffield for foot friction studies. Water was applied to the inside of the plantar region of the sock textiles to different levels using a moisture control protocol. The moisture level of both the 1MTH region and the sock fabrics were monitored throughout testing using a Corneometer® device.Increasing sock moisture above the dry condition was found to increase foot-sock sliding friction for both sock materials tested. No significant correlation was found at the level p < 0.05 between foot hydration level and sliding friction over the hydration range tested. In dry conditions, the cotton-rich sock exhibited lower levels of friction compared with the anti-blister sock. However, in both low moisture and wet conditions, the anti-blister sock showed comparatively lower levels of friction than the cotton-rich sock. This suggests that for intensive athletic events where significant perspiration is likely to occur, the anti-blister sock would provide lower friction. This study offers a new approach to friction testing of sock materials and it is hoped that its outcomes will provide new insights on the preventative measures for friction blisters

Thermo-physiological comfort and frictional characteristics of running socks in different moisture conditions

During prolonged walking and running, the plantar aspect of the foot is subjected to repetitive pressure and cycles of shearing, along with high levels of moisture due to perspiration and heat. The combination of all these elements not only affects comfort, but also provides an ideal condition for friction blister formation. The current study explored the physical properties of a predominantly nylon anti-blister sock and a cotton-rich sock along with their characteristics relevant to thermo-physiological comfort. The anti-blister fabric exhibited a slightly higher sliding friction than the cotton-rich fabric in dry condition. However, in the presence of moisture, the anti-blister fabric produced lower sliding friction than the cotton-rich fabric-which could be attributed to the low water vapour resistance and good one-way transport ability of anti-blister fabric. It is hoped that these results could be used to inform the actual frictional performance of the socks in different moisture settings, taking into account the propensity for sweating to occur