Development of a Thin Vibrotactile Actuator Based on the Electrostatic Force Mechanism for Large Haptic Touch Interfaces

Vibrotactile feedback in touch screen displays (TSDs) contributes to improved usability and enhanced engagement. It is prevalent in small consumer electronic devices, such as smart phones. While vibrotactile feedback is a desirable feature for large TSDs, it is limited in such devices due to a lack of proper actuators. In this study, we propose a thin vibrotactile actuator based on an electrostatic force mechanism suitable for mounting on the back of large TSDs. The primary goals of this study are to design and test a thin or slim electrostatic resonant actuator (ERA) and investigate its feasibility for large TSD applications. A prototype ERA was constructed by employing a “leaf” spring design to reduce the thickness and to support a mass that is grounded electrically. Upon applying a high-voltage input to the prototype, the electrostatic attraction force coupled with the spring’s restoring force makes the mass to oscillate, and the maximum vibration occurs at its resonant frequency. The ERA module testing shows that the prototype produced the maximum output acceleration of 2.5 g at its resonance frequency (99 Hz), which is significantly larger than the threshold value which humans can perceive. After validating that the thin ERA can produce sufficient vibrotactile sensations, a haptic touch display module consisting of a 17-inch touch panel supported by four ERAs was constructed. To experimentally evaluate the performance of this prototype, three distant input frequencies were used, and the acceleration response of the panel was measured at multiple points. The results show that the acceleration magnitude varies, exhibiting distinct patterns throughout the panel surface, when different input frequency values were applied. The results further show that the maximum acceleration magnitude is greater than that of the human-perceivable threshold values for the input frequencies considered in this study. Overall, the results show that the proposed ERA is feasible to use in large TSDs to convey vibration tactile sensations to users while keeping the thickness of the haptic interface module thin.