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Effect of Finger Orientation on Contact Stiffness and Area During Sliding
Introduction
Have you ever noticed how your sense of touch can vary when interacting with different surfaces, depending on how your fingers are positioned? Researchers from Koc University in Istanbul have been investigating how finger orientation affects the way we touch and feel surfaces. Their experimental findings show that the changes in the orientation of finger can alter the contact area and stiffness and hence, the frictional forces while exploring surfaces. The experiment involved sliding a smooth and flat surface beneath the index fingers of two participants, while their index fingers rotated about its long axis at different angles: 0°, 15°, 30°, and 45°. They measured how the contact area between the finger and the surface changed and tracked the friction during sliding. The researchers used high-tech tools, including a force transducer to measure friction forces and a high-speed camera to capture images of the finger’s contact with the surface. The setup allowed precise control of the finger’s rotation and sliding speed.
What They Found: Surprising Changes in Contact Area
Under 0° rotation angle, the contact area shrank slightly during the sliding. This result was expected and aligned with the earlier studies. But things got interesting when the index finger was rotated. For larger internal rotation angles (30° and 45°) of the index finger toward the thumb, something surprising happened. While sliding in the radial direction (away from the thumb), the contact area reduced as expected. However, sliding in the ulnar direction (toward the pinky) caused the contact area to increase. Yes, the finger actually touched more of the surface when it was rotated, which was unexpected. The researchers believe this happens because rotating the finger changes its radius of curvature and stiffness and causes asymmetric distribution of stresses.
Why It Matters?
So, why does any of this matter? This study sheds light on why certain everyday touch interactions feel different depending on how we use our fingers. Ever noticed how surface texture feels different when you slide your finger in a certain way? Or why gripping an object with your fingers at different angles can change the grip strength and stability? These small variations are due to changes in contact mechanics—precisely what this research explores. Understanding how finger orientation affects contact mechanics can improve the design of everyday objects, mobile devices, and even robotic hands. For example, imagine a touchscreen of a mobile device that responds to your touch and changes how it feels based on how you move your finger on its surface. This could enhance gaming experiences, virtual/augmented/mixed reality interactions, and remote communication that rely on haptic feedback.
Want to know more?
Check this link: https://ieeexplore.ieee.org/abstract/document/10778980
Author : Easa Ali Abbasi
