Data supporting the publication: Fingertip real contact area scales quadratically with input voltage in electrostatic actuation

Dataset of "Fingertip real contact area scales quadratically with input voltage in electrostatic actuation", which is accepted for Eurohaptics 2026.<br>Abstract:Touchscreens have become the dominant interface in consumer electronics, yet interactions with them remain primarily visual. Incorporating haptic feedback that simulates touch sensations could make these interactions more natural and intuitive. Electrostatic actuation, which modulates friction by attracting the finger toward a capacitive surface using an alternating voltage, offers a promising approach. The resulting increase in friction is often attributed to the rise in real contact area; however, direct experimental evidence linking voltage input parameters to real contact area and contact forces remains limited. Here, we use frustrated total internal reflection to directly image the real contact area while simultaneously measuring contact forces during controlled finger sliding under electrostatic actuation. We systematically vary voltage amplitude (75–150~V) and excitation frequency (30–230~Hz) and quantify the changes in contact area and forces as functions of these parameters. Our results reveal a quadratic dependence of real contact area, electrostatic attraction, and tangential force on voltage amplitude, with comparatively small effects of excitation frequency. These findings clarify the respective roles of voltage amplitude and frequency in the electrostatic modulation of finger contact mechanics, providing design guidelines for haptic display design.<br>The experiment consisted of five sessions, each conducted on a separate occasion. In each session, all combinations of four input voltage amplitudes (75, 100, 125, and 150 V) and five sine-wave frequencies (30, 80, 130, 180, and 230 Hz) were tested, with three repetitions per frequency-amplitude combination. Each trial consisted of a voltage-off phase followed by a voltage-on phase within the same sliding stroke. During each trial, the fingertip was moved laterally at a constant speed of 20 mm/s using the motorized stage, while the participant regulated the normal force to 1 N using real-time visual feedback. For each frequency-voltage combination, results were computed by averaging across the three repetitions within that session. <br>Details of the dataset can be found in the Readme file.