Real world environments, such as kitchens, present objects covered in viscous fluids: soap, oil, water, etc. Understanding and designing for slippery and submerged contact, where fluid lubrication is present, is a continuing challenge in the robotics community. Contact area, bending stiffness, and the presence of a viscous fluid affect friction. This work focuses on milliscale features (3 to 20 mm in size) of soft urethane skin on smooth, flat surfaces. We characterize the friction of soft skins, with varying size, and therefore bending stiffness, of cylindrical features, all with the same nominal contact area. In addition, a new method of frustrated total internal reflection with dye is introduced to visualize lubricated contact. We find that a small number of milliscale fingertip features maximizes friction force in the presence of lubrication, as compared both to un-patterned and many-featured skin designs. This holds true for a robotic gripper test, when pinching glass submerged in oil.

中文翻译：

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毫级特征增加润滑接触中柔软皮肤的摩擦

现实世界的环境，例如厨房，呈现出覆盖着粘性流体的物体：肥皂、油、水等。理解和设计光滑和浸入式接触，其中存在流体润滑，是机器人社区的一个持续挑战。接触面积、弯曲刚度和粘性流体的存在都会影响摩擦。这项工作的重点是光滑平坦表面上柔软的聚氨酯皮肤的毫级特征（尺寸为 3 到 20 毫米）。我们描述了软皮的摩擦，具有不同的尺寸，因此具有不同的弯曲刚度，具有相同的标称接触面积的圆柱形特征。此外，引入了一种用染料抑制全内反射的新方法，以可视化润滑接触。我们发现在润滑存在的情况下，少量的毫级指尖特征使摩擦力最大化，与无图案和多功能皮肤设计相比。这适用于机器人夹持器测试，当夹住浸在油中的玻璃时。