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.
Keywords: fretting phenomenon; large-area displays; localized vibrotactile sensation; multiple tactile feedback; relaxor ferroelectric polymers.