High-speed multi-channel 3-D Optical Coherence Tomography studies of the biomechanics of skin friction.

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The health of the skin has profound effects on both our physical and psychological well-being. Enormous academic and commercial effort is devoted to optimising the health and appearance of skin. The barrier function of skin has been widely studied, but less well studied is its role in providing enough friction to allow us to grip and manipulate objects. Excessive friction can produce undesirable skin conditions such as chaffing and irritation in many scenarios such as wearing a respiration face mask or the skin being in contact with a damp surface. Conversely reduction of skin friction can occur in old age and compound the difficulties experienced by the older population when gripping and manipulating objects.Many potential determinants of friction have been studied, including applied load, skin deformation, skin mechanical properties and surface textures and materials, but the sub-surface behaviour and skin strain has not been investigated as rigorously. Most of these parameters have been investigated statically and although it is known that they will change when the contact is dynamic no quantitative data is available for using in computer models of skin.The aim in this work will be to develop new imaging techniques to allow sub-surface observation of how skin behaves when it is sliding against an object and what influences this the most, for example, skin moisture, applied load, sliding speed etc. The contact area between skin and object will also studied in greater detail than before as this has a major effect on friction and as yet no techniques exist for characterising this in a moving contact.The objectives of the work will initially focus on developing the equipment and techniques needed to observe the surface and sub-surface behaviour. These will then be combined with skin testing apparatus to allow the measurements of friction etc. to be taken in parallel with the sub-surface images.The information from the tests and the techniques themselves will then be applied in three practical case studies to ensure real world impact for the work. The first will involve working with Philips on studying facial masks used by sleep apnea sufferers. Test data will help improve computer models of the contact between facial skin and a mask. The second will be carried out with Unilever and focus on characterising the effects of skin creams and cleansers. The final case study will be on using the new non-invasive imaging technique in clinical studies carried out by dermatologists at The University of Sheffield to replace tape-stripping methods currently used to study skin damage.