No description available.

Unique to the sense of touch is that it is created through physical interaction. Through exploring the world with our skin we discover its properties, its shape, textures and materials, allowing us to meaningfully interact with it. This places great emphasis on the mechanical properties of our skin, the organ of touch, and no more so than the 'glabrous' skin of the finger pads and palms of our hands. Through a wide and multi-disciplinary review of touch, and observations of the macro and microstrutures of glabrous skin, this thesis develops an understanding of the key mechanical properties of this specialised skin, and presents a new hypothesis for the existence of an edge-encoding functional morphology. This thesis presents significant benefits to tactile end effector design that can be gained through mimicking the key mechanical structures of human glabrous skin. A new tactile end-effector design is presented and tested, which successfully demonstrates the capture of these key functional properties, creating a highly sensitive and accurate extraction of tactile features from a touched scene. This prototype device is both a practical and highly capable tactile sensing end effector. It achieves significant levels of compliance, sensitivity, contact surface area and strength for practical use in active exploration, and in grasping and manipulation of objects. The prototype device is strong, robust, reliable, simple and cheap to manufacture

No description available.

No description available.

The aims of the research project described in the thesis were to investigate the mechanical properties of skin, to develop relevant analytical concepts and to explore clinical applications. Chapter I gives a review of the published literature, consisting of a brief description of the anatomy of skin, a more detailed survey of the nature and mechanical properties of the components of skin and a critical review of all known work on the mechanical properties of skin. The pilot experiments which were carried out to define the nature and extent of the problems involved in testing skin are described in Chapter II. Various theoretical approaches to describe the behaviour of skin are considered in Chapter III, including a semi-empirical network concept and the general theory of continuum mechanics applied to biological tissue. Chapter IV contains a detailed description of the development of testing methods up to and including the highly refined uniaxial, constant strain rate technique which was eventually used. Stress relaxation and creep tests are also described. The results obtained are analysed in Chapter V. Various attempts to develop in vivo testing techniques are described in Chapter VI and possible clinical applications of the work covered in this thesis are discussed in Chapter VII. There is an extensive bibliography and various appendices, presenting the details of experimental and analytical techniques which were not fully discussed in the main text. No separate list of the mathematical notation employed is given as each symbol is explained as it arises.

La peau, organe le plus étendu du corps humain, réalise une barrière entre l’environnement et le milieu interne préservant ainsi l’homéostasie. De nombreuses fonctions sont assurées par le tégument telles une modulation des échanges thermiques, une barrière physique, chimique et immunitaire contre l’entrée des composés et microorganismes exogènes mais également contre la perte des substances du milieu interne. L’altération de la surface cutanée et donc de ses fonctions, engendre un processus complexe de réparation qui vise à restaurer le système. Lors de ce travail de thèse des outils biophysiques ont été expérimentés dans un premier temps afin de renseigner sur la qualité de la fonction barrière, et donc sur la qualité de la cicatrisation cutanée. La première approche consistait à quantifier la qualité de la barrière cutanée par mesure de la perte insensible en eau. Cette approche s’est révélée fructueuse et a été proposée comme standard interne dans les études de perméation cutanée ex vivo afin de permettre une comparaison plus aisée des résultats expérimentaux issus de différentes préparations de peau. Dans un second temps la mesure des paramètres du micro relief cutané a été confrontée aux résultats des mesures concomitantes des paramètres biophysiques classiques (perte insensible en eau et hydratation cutanée) afin de mettre en évidence une possible corrélation entre qualité de la fonction barrière cutanée et topologie de surface. Les résultats des deux méthodes d’investigation sont effectivement bien corrélés dans le cas d’une altération physique de la surface cutanée, suggérant les mesures des paramètres du micro relief cutané comme une méthode originale de quantification de la réépithélialisation cutanée. Une approche plus fondamentale a également été éprouvée afin d’appréhender les mesures de « pertes insensibles en oxygène » comme une mesure innovante de la qualité de la fonction barrière cutanée. Cette première approche a permis de mettre en évidence, une orientation préférentielle significative du flux d’oxygène à travers la peau.La deuxième partie de ce travail de thèse a consisté à développer une nouvelle formulation pro cicatrisante et de tester son potentiel thérapeutique in vitro. Initialement basée sur l’administration d’oxygène afin de lutter contre l’hypoxie qui accompagne souvent les lésions cutanées, cette ligne d’étude a rapidement été écartée au profit du développement d’une formulation pour l’établissement d’un stress oxydant améliorant les processus de cicatrisation. Cette théorie du stress oxydant comme promoteur de la cicatrisation découle d’observations récentes qui démontrent un retard de cicatrisation en l’absence d’un stress oxydant in vivo, et une stimulation spécifique des cellules in vitro. Les formulations développées à ce dessein ont été testées sur des cultures de kératinocytes in vitro afin d’étudier leurs effets sur la réépithélialisation : l’une des dernières étapes de la cicatrisation. / Skin, the largest organ of the human body, confers protection from the environment through several barrier functions which provide physical, immune and chemical defenses. Skin provides protection to microorganisms, exogenous compounds, shocks, radiations, temperature and out flowing of solutes or water from the body. Without an efficient system to restore skin structures and functions, skin wounding may be deleterious. Over the course of this Ph.D. work, varied biophysical parameters have been experienced as tools to investigate the cutaneous wound healing quality. Measurement of transepidermal water loss (TEWL) to quantify the barrier function quality of the skin has been successfully assessed. It has been proposed as an internal standard of skin integrity facilitating direct comparison of data issued from different skin samples. In an in vivo approach, skin micro-relief parameters have been set against TEWL and hydration values after a physical or chemical damage onto the skin. Interestingly micro-relief parameters and biophysical measurements were closely related after tape-stripping, suggesting topographical parameters as an original method to quantify skin reepithelialization. A more fundamental assay was performed suggesting oxygen flux as a new tool to investigate skin barrier quality. From our results a “transepidermal oxygen loss” development seems to be compromised but surprisingly, we pointed out a preferential oxygen delivery course through the skin from endogenous reservoir. Besides the improvement of these tools for wound healing assessment, an innovative formulation to promote skin wound healing has been developed. The challenge of this new preparation is to generate reactive oxygen species, namely hydrogen peroxide, at sub-cytotoxic levels. Indeed recent studies pointed out that down regulation of hydrogen peroxide production in vivo delayed wound healing; furthermore, in vitro stimulation of fibroblasts or keratinocytes with hydrogen peroxide induced expression of healing promoting factors. The developed formulation was therefore assayed on keratinocytes’ in vitro culture in order to evaluate their efficacy on réépithélialisation, ending wound closure. Interestingly one of the developed formulation stimulated significantly keratinocytes migration, through a mechanism which do not imply TGF-1 expression, suggesting a potential benefit in wound réépithélialisation.