Microstructured dielectric elastomer-based flexible tactile display resistant to large contact force

Abstract

Flexible and wearable electronic devices have received much attention as a promising candidate to satisfy the demands for revolutionary designs for human-computer interaction. Since tactile interface has been consid-ered an essential component for contemporary electronic devices, technologies to implement tactile sensing and feedback functionality on flexible geometries have been widely studied. To provide tactile feedback with me-chanical robustness against geometric changes, electro-active polymers (EAPs), particularly dielectric elasto-mers (DEs) have been used for soft actuators. Although many approaches provide a promising route to human-perceivable tactile response on flexible interfaces, there are still challenges in securing reliable tactile feedback against pressurized contact, and in designing a resonance frequency to be in the human-sensitive frequency range of perception for vibration acceleration (100？200Hz). For practical wearable device applications, we proposed a novel flexible tactile actuator with a microstructured DE layer that is capable of producing robust vibrotactile response under high external pressure as high as 20 kPa, which is a typical pressure for user’s touch. The actuator is capable of tuning the dynamic performance by modulating mechanical and dielectric properties of the DE layer through the geometry-dependent microstructuring. Experimental evaluations of vibrational per-formance with changing geometric parameters of the pyramidal microstructured DEAs (PMDEAs) and cuboidal microstructured DEAs (CMDEAs) revealed that the mechanical and dielectric properties should be balanced to optimize the performance. Due to the benefit of nonlinearity that the pyramidal structure provides, PMDEAs could produce high mechanical output under various external pressures in the frequency range of 100？200 Hz, whereas CMDEAs were difficult to design the resonance in the desired frequency range. Psychophysical exper-iments showed that the PMDEAs could provide perceivable tactile feedback effectively under various external pressures than CMDEAs. A 3 × 3 array tactile display was developed with the PMDEA, which height and spatial distance is 250 μm and 500 μm, respectively, to provide multi-touch haptic feedback in wearable devices. A user test clearly showed that reliable tactile information could be effectively transmitted under user’s pressur-ized contact. A PMDEA-based tactile display, which has not only fast, reversible, and highly durable responses but also high-pressure endurance characteristics has potential for practical wearable device applications.