Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
Department of Cognitive Robotics, Delft University of Technology, Delft, CD, The Netherlands.
PLoS One. 2022 Jul 13;17(7):e0269722. doi: 10.1371/journal.pone.0269722. eCollection 2022.
Pressing the fingertips into surfaces causes skin deformations that enable humans to grip objects and sense their physical properties. This process involves intricate finger geometry, non-uniform tissue properties, and moisture, complicating the underlying contact mechanics. Here we explore the initial contact evolution of dry and hydrated fingers to isolate the roles of governing physical factors. Two participants gradually pressed an index finger on a glass surface under three moisture conditions: dry, water-hydrated, and glycerin-hydrated. Gross and real contact area were optically measured over time, revealing that glycerin hydration produced strikingly higher real contact area, while gross contact area was similar for all conditions. To elucidate the causes for this phenomenon, we investigated the combined effects of tissue elasticity, skin-surface friction, and fingerprint ridges on contact area using simulation. Our analyses show the dominant influence of elastic modulus over friction and an unusual contact phenomenon, which we call friction-induced hinging.
按压指尖会导致皮肤变形，从而使人类能够握持物体并感知其物理特性。这个过程涉及复杂的手指几何形状、不均匀的组织特性和水分，这使得潜在的接触力学变得复杂。在这里，我们探索了干燥和湿润手指的初始接触演变，以分离控制物理因素的作用。两名参与者在三种水分条件下逐渐将食指压在玻璃表面上：干燥、水合和甘油水合。通过光学测量随时间的总接触面积和真实接触面积，结果表明甘油水合产生了惊人的更高的真实接触面积，而所有条件下的总接触面积都相似。为了阐明这一现象的原因，我们使用模拟研究了组织弹性、皮肤表面摩擦和指纹脊对接触面积的综合影响。我们的分析表明，弹性模量对摩擦的影响占主导地位，以及一种不寻常的接触现象，我们称之为摩擦诱导的枢轴。
