Abstract
This study proposes a novel skinny button with multimodal audio and haptic feedback to enhance the touch user interface of electronic devices. The active material in the film-type actuator is relaxor ferroelectric polymer (RFP) poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] blended with poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], which produces mechanical vibrations via the fretting vibration phenomenon. Normal pressure applied by a human fingertip on the film-type skinny button mechanically activates the locally concentrated electric field under the contact area, thereby producing a large electrostrictive strain in the blended RFP film. Multimodal audio and haptic feedback is obtained by simultaneously applying various electric signals to the pairs of ribbon-shaped top and bottom electrodes. The fretting vibration provides tactile feedback at frequencies of 50–300 Hz and audible sounds at higher frequencies of 500 Hz to 1 kHz through a simple on-off mechanism. The advantage of the proposed audio-tactile skinny button is that it restores the “click” sensation to the popular virtual touch buttons employed in contemporary electronic devices.
Highlights
Multimodal human-machine interfaces are becoming increasingly popular in a wide range of applications for enhancing the quality of human-machine interaction and the user experience when users scan or touch the machine surface with their fingertips[1,2,3,4,5,6]
The flexible touch layer comprises a touch sensor located underneath a scratch-resistant polyethylene terephthalate (PET) cover, a top electrode made of silver nanowires (AgNWs), and a blended relaxor ferroelectric polymer (RFP) film
If a bump is located underneath the bottom electrode and permanent contact is achieved between the RFP film and bottom electrode as shown in Fig. 1d, a human fingertip can feel the vibration with a gentle touch on the button
Summary
Multimodal human-machine interfaces are becoming increasingly popular in a wide range of applications for enhancing the quality of human-machine interaction and the user experience when users scan or touch the machine surface with their fingertips[1,2,3,4,5,6]. When a human fingertip applies normal pressure to the touch button, a local electric field is mechanically activated on the contact area between the RFP film and the bottom electrode, which produces a large electrostrictive strain in the RFP film. When electrical voltage signals with frequencies ranging from 50 Hz to 300 Hz or 500 Hz to 20 kHz are applied to the ribbon-shaped electrodes of one skinny touch button, tactile vibrations or audible sound are simultaneously generated, respectively. The skinny button provides the tactile-feedback vibrations at frequencies of 50 Hz to 300 Hz and audible sounds at higher frequencies of 500 Hz to 20 kHz via a simple on-off mechanism With this simple structure, the audio-tactile skinny button can be integrated with capacitive touch sensors, resistive touch sensors or inductive touch sensors without any physical interference. The audio-tactile skinny button developed in this study has the ability to provide the multimodal “click” sensation currently lacking from touch buttons in electronic devices
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