Frequency-Dependent Behavior of Electrostatic Forces Between Human Finger and Touch Screen Under Electroadhesion

Area of Science:

• Physics
• Materials Science
• Human-Computer Interaction

Background:

• Existing circuit models fail to accurately represent electroadhesion forces between human fingers and touch screens.
• Observed electrostatic forces change significantly with stimulation frequency, a behavior not captured by current models.

Purpose of the Study:

• To experimentally measure and theoretically model the frequency-dependent electrostatic forces during electroadhesion.
• To develop an improved electro-mechanical model that accounts for charge dynamics at the interfaces.

Main Methods:

• Conducted experiments measuring voltage-induced frictional forces across a wide range of stimulation frequencies (1 Hz to 1 MHz).
• Estimated electrostatic force magnitude as a function of frequency using friction coefficients.
• Developed a novel electro-mechanical model integrating electric field laws and multi-scale contact mechanics, incorporating charge accumulation and transfer.

Main Results:

• Experimental data revealed electrostatic force follows an inverted parabolic curve, peaking around 250 Hz.
• The proposed model demonstrated good agreement with experimental findings.
• Model analysis indicated charge leakage from the Stratum Corneum (SC) below 250 Hz and SC electrical properties above 250 Hz dictate force magnitude.

Conclusions:

• The developed electro-mechanical model provides a more accurate representation of finger-touch screen electroadhesion compared to existing models.
• Understanding frequency-dependent charge dynamics is crucial for optimizing electroadhesion performance.
• This research offers insights into the physical mechanisms governing electroadhesion across various frequencies.