Understanding the properties and consequences of friction under light normal loads is fundamental to areas such as tactile sensing, haptic systems used in robotic gripping of sensitive objects, and characterization of products rangıng from the softness of fabrics to effects of lotions on skin. In tactile sensing, as a finger is lightly rubbed over a surface, the mechanoreceptors in the dermis become excited and send signals to the brain for processing. Their excitation results from the asperities, adhesion, and other geometric and chemical surface properties that come into contact with the skin. These same sources also give rise to vibration and sound as two surfaces are in sliding friction even under light load, such as a finger pad over a silk fabric. Whereas the mechanoreceptors respond around 200 - 300 Hertz, spectrum of the actual sounds and vibrations that are generated can go beyond these values, thus presenting additional opportunities for surface characterisation through the acoustics response. Only a limited number of those address friction sounds and vibrations under light loads. Studies that address soft materials have not yet been reported. Much of the previous work in this area relates to perception and tactile sensing with limited attention to the generation mechanisms of sound and vibration between soft surfaces. The proposed project builds on the principle investigator's experience in this area for the past two decades. The project will focus on modeling friction forces over an area the size of a finger pad that moves over a surface and develop predictive models of the sound and vibration that emanate from such a moving contact area. The novelty the project brings includes consideration of materials and also adhesive surfaces, which are important in gripping. Another outcome of this project will be a new test set up that can mimic a finger rubbing over a material under light friction and has the ability simultaneously measure dynamic quantities.
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