Electrostatic Friction Displays to Enhance Touchscreen Experience

Touchscreens are versatile devices that can display visual content and receive touch input, but they lack the ability to provide programmable tactile feedback. This limitation has been addressed by a few approaches generally called surface haptics technology. This technology modulates the friction between a user’s fingertip and a touchscreen surface to create different tactile sensations when the finger explores the touchscreen. This functionality enables the user to see and feel digital content simultaneously, leading to improved usability and user experiences. One major approach in surface haptics relies on the electrostatic force induced between the finger and an insulating surface on the touchscreen by supplying high AC voltage. The use of AC also induces a vibrational sensation called electrovibration to the user. Electrostatic friction displays require only electrical components and provide uniform friction over the screen. This tactile feedback technology not only allows easy and lightweight integration into touchscreen devices but also provides dynamic, rich, and satisfactory user interfaces. In this chapter, we review the fundamental operation of the electrovibration technology as well as applications have been built upon

Tactile Roughness Perception of Virtual Gratings by Electrovibration

Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with 10 participants to investigate the effect of spatial period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants' finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with spatial period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force ($dF_t/dt$) as a function of spatial period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.Comment: Manuscript received June 25, 2019; revised November 15, 2019; accepted December 11, 201

Modern Applications of Electrostatics and Dielectrics

Electrostatics and dielectric materials have important applications in modern society. As such, they require improved characteristics. More and more equipment needs to operate at high frequency, high voltage, high temperature, and other harsh conditions. This book presents an overview of modern applications of electrostatics and dielectrics as well as research progress in the field

Investigation on Low Voltage Operation of Electrovibration Display

This paper presents three methods of input voltage signals that allow low voltage operation of an electrovibration display while preserving the perceptual feel and strength of electrovibration stimuli. The first method uses the amplitude modulation of a high-frequency carrier-signal. The second method uses a dc-offset, and the third method uses a combination of the two methods. The performance of the three methods was evaluated by a physical experiment that measured and analyzed static (dc-component) and dynamic (vibratory component) friction forces and two subsequent psychophysical studies. The physical experiment showed that only the dc-offset method enabled a statistically significant increase in the static friction force between the fingertip and the surface of the electrovibration display. The static friction increase was closely related to the root mean square of input voltage level. In contrast, all of the three methods increased the dynamic friction force significantly, which was deemed to be related to the high frequency effect validated in the previous literature. The first psychophysical study showed that the three proposed methods can significantly reduce the peak-to-peak (p-p) amplitude of an input voltage signal while generating perceptually equally strong electrovibrations to that produced by the conventional method. Using lower p-p voltage has the merits of a simpler electrical circuit and less electromagnetic noise, saving the overall system cost. Further, the perceived intensity of electrovibration was more correlated to the dynamic friction force than the static friction force. The second psychophysical study was a discrimination experiment, and it demonstrated that all the three proposed methods and the conventional method can provide perceptually similar stimuli despite their different signal forms and voltage amplitudes. Our experimental investigation allowed us to conclude that the dc-offset method is the best way to lower the driving voltage of an electrovibration display while providing perceptually equivalent electrovibrations.115sciescopu