The Effect of Applied Normal Force on the Electrovibration

Area of Science:

• Haptics and Human-Computer Interaction
• Tribology and Surface Science

Background:

• Electrovibration is a key technology for creating tactile feedback on touchscreens.
• Previous research indicates normal force influences electrostatic force, primarily by changing contact area.

Purpose of the Study:

• To investigate if normal force affects electrostatic force independently of apparent contact area.
• To quantify the relationship between normal force, electrostatic force, and air gap thickness.

Main Methods:

• Measured tangential force during finger sliding on a touchscreen at varying normal forces (0.5-4.5N) with constant apparent contact area.
• Utilized a recently proposed electrostatic force model incorporating air gap effects to analyze measurements.

Main Results:

• Electrostatic force significantly increased with normal force.
• Air gap thickness was found to decrease as normal force increased, following a power function relationship.
• The air gap thickness is significantly affected by normal force.

Conclusions:

• Normal force plays a critical role in electrovibration tactile feedback, even when apparent contact area is constant.
• The observed changes in air gap thickness due to normal force are essential for accurate tactile feedback system design.