Texture design for skin friction and touch perception of stainless steel surfaces

Abstract

SummaryTactile perception a concept with mechanical, physiological and psychological perspective, is of particular concern to the industrial companies and research area. The hedonic attributes of tactile perception are influential to our daily life like wearing clothes, using personal care products, holding tool handles or in domestic appliances. In a more general case, the tactile perception of surfaces of domestic appliances greatly affects the quality of our daily life.Stainless steel is one of the most common materials used in automobile, architecture, kitchenware and medical applications. In order to fabricate the pre-defined deterministic surface texture on the stainless steel material, the micro-fabrication techniques are investigated and discussed. Micro-casting, Chemical Wet Etching, Plasma Etching, Laser Surface Texturing LST and 3D Printing are the major fabrication methods to produce deterministic micro-structure in micro scale detail. In this thesis, LST is chosen to be the main fabrication method for producing the surface texture due to its accuracy and ability to fabricate on stainless steel sheet material.A skin contact model was modified based on Hertzian and Westergaard model to take into account the influence of surface texture and orientation effect. This two-term friction model enables the prediction of the contact area, sliding friction between the skin and counter-surface.Furthermore, the tactile perception involved textures were designed and investigated in both perception experiments and skin friction measurements. The thesis focusses on the relationships among tactile perception, sub-micron surface roughness features and friction at light touch conditions, with the general aim to discover design principles that enhance tactile perception.For the perception experiments, a panel test was conducted and the subjective ratings from 0 to 10 were graded by each participant to describe the level of perceived roughness, perceived stickiness and perceived comfort. For the skin friction measurements, a multi-axis force/torque transducer was used to measure the dynamic friction between skin and counter-surface in vivo.The correlation of the perception experiment and friction measurement provides design tools for texture design of future product surfaces. With the presented tactile friction model, a strategy was extracted for optimizing surfaces with respect to tactility. The pivotal element is minimizing the adhesion term of friction by minimizing the contact area by designing a surface texture with minimal contact area in sliding motion. In addition, the orientation effect is another key factor for the texture design. The results of the study can be beneficial to understand the tactility related research and product developments in the future.