Tactile Perception of Electroadhesion: Effect of DC versus AC Stimulation and Finger Moisture

TL;DR

This study investigates how electroadhesion tactile feedback is perceived under DC and AC stimulation, revealing lower detection thresholds for AC signals and the influence of finger moisture on perception, with implications for various applications.

Contribution

It provides new insights into the tactile perception mechanisms of electroadhesion, especially the effects of AC versus DC stimulation and finger moisture, supported by experimental and impedance measurements.

Findings

AC signals have lower voltage detection thresholds than DC signals.

Moist fingers exhibit higher detection thresholds due to increased conductivity.

Finger moisture significantly reduces impedance at the interface.

Abstract

Electroadhesion has emerged as a viable technique for displaying tactile feedback on touch surfaces, particularly capacitive touchscreens found in smartphones and tablets. This involves applying a voltage signal to the conductive layer of the touchscreen to generate tactile sensations on the fingerpads of users. In our investigation, we explore the tactile perception of electroadhesion under DC and AC stimulations. Our tactile perception experiments with 10 participants demonstrate a significantly lower voltage detection threshold for AC signals compared to their DC counterparts. This discrepancy is elucidated by the underlying electro-mechanical interactions between the finger and the voltage-induced touchscreen and considering the response of mechanoreceptors in the fingerpad to electrostatic forces generated by electroadhesion. Additionally, our study highlights the impact of moisture on electroadhesive tactile perception. Participants with moist fingers exhibited markedly higher threshold levels. Our electrical impedance measurements show a substantial reduction in impedance magnitude when sweat is present at the finger-touchscreen interface, indicating increased conductivity. These findings not only contribute to our understanding of tactile perception under electroadhesion but also shed light on the underlying physics. In this regard, the results of this study extend beyond mobile devices to encompass other applications of this technology, including robotics, automation, space missions, and textiles.