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Research Topic on Fingerpad Contact Mechanics

Antonio Papangelo's picture

Our research Topic on Fingerpad Contact Mechanics is still open! Please follow the link below for abstract submission!


Electrovibration is a powerful technology in surface haptics providing efficient tactile feedback on capacitive touchscreens. For this purpose, an alternating electric potential is applied to the conductive layer of the screen which results in electrostatic attraction between the skin of the moving finger and the touch surface that in turn increases friction. The latter can be controlled by modulating the waveform, amplitude, and frequency of the input voltage to create realistic virtual textures and shapes. Due to the variety of potential applications of this kind of variable friction displays in smartphones, tablets, navigation devices or interactive kiosks, the long-known effect of electrovibration has regained great interest, triggering intensive research. However, although some very instructive experimental and theoretical works have emerged from it, our knowledge of the underlying contact mechanics processes remains limited. This is not surprising, since human skin exhibits very complex tribological behavior even without electroadhesion. It consists of a multilayered, anisotropic non-linear viscoelastic material with a multiscale roughness on its surface. In addition, the material properties are strongly influenced by the skin hydration level, and tribological properties depend on environmental conditions like temperature or humidity and lubrication as well. Thus, appropriate modeling and simulation with the aim to correctly reproduce all contact mechanical quantities is a major challenge.

This Research Topic is intended to contribute to a deeper understanding of the contact mechanics and friction behind electrovibration. In particular, the aim is to clarify which of the various effects occurring in the skin-solid interface predominate the finger pad friction under electroadhesion. We encourage submissions on experimental measurements, theoretical and numerical modelling of the contact mechanics problem. Numerous tribological phenomena which occur in the frictional contact between finger and screen under electroadhesion can already be observed in those without electroadhesion. Therefore, studies that do not take electrostatic actuation into account are welcome as well. Submitted manuscripts on the research topic may include, but are not limited to:

• Adhesion mechanisms: Van der Waals, capillary and electroadhesion
• Influence of amplitude, shape, and frequency of excitation on friction
• Improved optical methods and new methods based on ultrasonic impedances to measure the (real) contact area with/without electrostatic attraction
• Evolution of the (real) contact area from pure normal contact to gross slip for human skin
• Capillary forces and electrowetting
• Roughness-induced hysteresis in normal contact under adhesion/electroadhesion
• Stimulation of tactile mechanoreceptors
• Influence of skin hydration and occlusion of moisture on interfacial gap impedance and friction
• Interfacial shear strength and adhesion- versus pressure-controlled friction
• Multiscale simulations and macroscopic approaches considering the internal layered structure of the finger, its nonlinear material behavior, as well as large deformations

Dr. Brygida Dzidek now runs the company "Haptology" but this Research Topic relates to her previous research as a research fellow at the University of Birmingham. All other Topic Editors declare that they have no competing interests related to the research topic.


Keywords: Electroadhesion, Surface Haptics, Contact Mechanics, Roughness, Electrowetting, Tactile Perception, Biotribology