Localized Fretting-Vibrotactile Sensations for Large-Area Displays

Abstract

Tactile perception in large-area displays is currently attracting substantial research attention since, in conjunction with visible and auditory sensations, it provides more immersive and realistic interactions with displayed contents. Here, a new vibrotactile display based on the fretting phenomenon is developed for the first time to provide localized tactile feedback on a large-area display. Normal pressure by a human fingertip activates a locally concentrated electric field in a relaxor ferroelectric polymer (RFP) film under the contact area, which produces a localized electrostrictive strain. The synergistic interplay among the localized electric field, electrostrictive deformation of the RFP film, and contact area dramatically amplifies acoustic vibrations near the contact edge of a human fingertip. A blend of poly(vinylidene fluoride−trifluoroethylene−chlorofluoroethylene) terpolymer and poly(vinylidene fluoride−trifluoroethylene) (55:45) copolymer is proposed for the RFP to provide an enhanced actuation performance even at elevated temperatures. The fretting-vibrotactile mechanism has several interesting properties, such as tactile feedback on a stationary fingertip, pressure-responsive simple on−off mechanism, multitouch interaction, excellent transparency, and easy integration with capacitive or resistive touch sensors and friction-based haptic-feedback mechanisms. An array of RFP film vibrators can provide addressable content-related multiple tactile feedback on large-area displays by modulating the frequency, amplitude, and profile of the driving voltage signals.

Wearable Soft Technologies for Haptic Sensing and Feedback

“…Most commercial vibrotactile actuators are based on eccentric mass‐based EM motors, [ 88 ] piezoelectric oscillating masses (Figure 8 Ai), [ 83 ] or membranes. [ 89 ] They are small, light, and low power. However, the resonant frequency of piezoelectric beams is fixed, and motors have slow spin‐up time and cannot change the frequency independently of the amplitude.…”

Low‐Voltage Soft Actuators for Interactive Human–Machine Interfaces

“…Reproduced with permission. [320] Copyright 2019, ACS Publications. e) Digital image of PVDF-TrFE-CTFE guide wire that bends with voltage application.…”

“…[304] Owing to the favorable characteristics of ferroelectric actuators, these actuators have been utilized for iHMI applications such as haptics or medical devices. [320][321][322][323][324][325][326] Localized tactile feedbacks have been realized through fretting-vibrotactile displays that are composed of a RFP and a top electrode while separated from the bottom electrode on a substrate by a spacer (Figure 15d). [320] To activate the display, normal pressures from the human finger push the RFP to contact the bottom electrode upon which a locally concentrated electric field is generated below the finger to induce localized electrostrictive strains.…”

“…[320][321][322][323][324][325][326] Localized tactile feedbacks have been realized through fretting-vibrotactile displays that are composed of a RFP and a top electrode while separated from the bottom electrode on a substrate by a spacer (Figure 15d). [320] To activate the display, normal pressures from the human finger push the RFP to contact the bottom electrode upon which a locally concentrated electric field is generated below the finger to induce localized electrostrictive strains. As such, localized multitouch feedbacks can be realized locally with favorable performances under static pressures.…”

“…Furthermore, the display can be easily integrated with various sensors and can be fabricated on the large scale. [320] Owing to the high flexibility and fast response of ferroelectric polymer actuators, these devices have been considered for steerable guide wires used for minimally invasive surgeries. [326] To achieve steerability, Ganet et al modeled and designed PVDF-TrFE-CTFE tube actuators with segmented electrodes that allowed two degrees of freedom (Figure 15e).…”