A “tactile white” for the fingertip: structuring materials for low friction

指尖的“触觉白色”：低摩擦的结构材料

• 批准号: 466754480
• 负责人: Professor Dr. Roland Bennewitz
• 金额: --
• 依托单位: Leibniz-Institut für Neue Materialien gGmbH (INM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/466754480?language=en
• 关键词: tactile; white; fingertip; structuring; materials

Friction between materials and the human fingertip is an essential part in our everyday life. It gives us the grip to handle objects and is key ingredient in tactile perception, providing us with the input for haptic recognition and affective touch. Flat surfaces offer good contact with the skin and a strong sticking, for example to lift a glass bottle. Rippled surfaces deform the skin and give better grip, for example to turn the lid and open the bottle. However, tactile functions of surface structures go beyond grip: They transport information, steer attention, and appeal to us. Already today most of the surfaces we touch are engineered. The demand for sustainable design and digital interfaces will increase the need to develop surfaces with haptic functions and attractions. Neither flat nor rippled surfaces are particularly appealing to touch, while surfaces with a fine texture offer low friction and the pleasant feel of silk. In this project, we explore the physics underlying the friction of small-scale random roughness and develop design rules for materials with a surface microstructure that provides lowest fingertip friction. In a classical two-term description, friction forces originate in adhesive shear at the skin-material interface and in deformation of the skin through roughness asperities. Low friction can be achieved when the interfacial contact area is reduced by increasing surface roughness while limiting deformation of the skin through protruding surface asperities. For the case of fingertip friction, contact mechanics depend not only on surface texture, but also on the papillary ridge structure at the fingertip. Therefore, an optimization of the surface texture also involves its spatial spectrum with respect to distances between papillary ridges. For our experiments we calculate surfaces with defined spectral properties and produce prototypes by advanced additive manufacturing. Tactile exploration experiments with many participants provide us with the data to validate models for fingertip friction as function of the spectral composition of roughness.We also explore the perception of friction by participants. We are particularly interested to reveal possible differences in the perception of interfacial and deformation friction when varying the roughness amplitude at certain length scales. The results will shed new light on the roles of roughness and friction in materials perception. The low friction and the irregular force fluctuations produced by our randomly rough surfaces are expected to result in a smooth, pleasant touch. The successful project will thus result in a better understanding of skin friction on natural and engineered surfaces. It will provide us with design rules for pleasant surface structures which may be described as a “tactile white” standard and thus offer a novel starting point for the creation of materials with tactile contrast and haptic functions.

材料与人类指尖之间的摩擦是我们日常生活中的重要组成部分。它为我们提供了处理物体的抓力，是触觉感知的关键要素，为我们提供了触觉识别和情感触摸的输入。平坦的表面可与皮肤良好接触并具有很强的粘附力，例如举起玻璃瓶。波纹表面使皮肤变形并提供更好的抓握力，例如转动盖子和打开瓶子。然而，表面结构的触觉功能超出了抓握的范围：它们传输信息、引导注意力并吸引我们。如今，我们接触到的大部分表面都已经经过工程设计。对可持续设计和数字界面的需求将增加开发具有触觉功能和吸引力的表面的需求。平坦或波纹表面的触感都不是特别吸引人，而纹理细腻的表面则具有低摩擦力和丝绸般的舒适触感。在这个项目中，我们探索了小尺度随机粗糙度摩擦背后的物理原理，并为具有可提供最低指尖摩擦的表面微观结构的材料开发了设计规则。在经典的两术语描述中，摩擦力源自蒙皮-材料界面处的粘着剪切力以及蒙皮通过粗糙度粗糙度的变形。当通过增加表面粗糙度来减少界面接触面积，同时通过突出的表面粗糙度限制蒙皮的变形时，可以实现低摩擦。对于指尖摩擦的情况，接触力学不仅取决于表面纹理，还取决于指尖的乳头脊结构。因此，表面纹理的优化还涉及其关于乳头脊之间距离的空间谱。在我们的实验中，我们计算具有定义的光谱特性的表面，并通过先进的增材制造生产原型。许多参与者进行的触觉探索实验为我们提供了数据来验证指尖摩擦力作为粗糙度光谱组成函数的模型。我们还探索了参与者对摩擦力的感知。我们特别感兴趣的是揭示当在一定长度尺度上改变粗糙度幅度时界面和变形摩擦的感知可能存在的差异。研究结果将为了解粗糙度和摩擦力在材料感知中的作用提供新的线索。我们的随机粗糙表面产生的低摩擦力和不规则的力波动有望带来光滑、舒适的触感。因此，该项目的成功将使人们更好地了解自然和工程表面上的皮肤摩擦。它将为我们提供令人愉悦的表面结构的设计规则，可以被描述为“触觉白色”标准，从而为创建具有触觉对比和触觉功能的材料提供一个新颖的起点。