Flexible and Transparent\nElectrovibration-Based Haptic\nDisplay with Low Driving Voltage

Electrovibration haptic technology, which provides tactile\nfeedback\nto users by swiping the surface with a finger via electroadhesion,\nshows promise as a haptic feedback platform for displays owing to\nits simple structure, ease of integration with existing displays,\nand simple driving mechanism. However, without electrical grounding\non a user’s body, the frequent requirement of a high driving\nvoltage near 50 V limits the use of electrovibration haptic technology\nin practical display applications. This study introduces materials\nand fabrication strategies that considerably reduce the driving voltage.\nWe used a transparent poly(vinylidene fluoride) (PVDF) thin film deposited\non transparent conductive polymers through a simple spin-coating process,\nthereby enabling easy integration with existing display technologies.\nThe high dielectric constant characteristics of PVDF enabled the production\nof tactile cues at low voltages (approximately 15 V), which are within\nthe safety limits of common electronics. We verified the feasibility\nof our electrovibration haptic feedback system on the basis of the\nabsolute threshold voltage through two-alternative forced choice psychological\ntests. The results revealed that the PVDF dielectric layer exhibited\na relatively lower absolute threshold than commonly used polymer films,\nwhich possess a relatively lower dielectric constant. To validate\nthe tactile attributes, a Likert five-point scale survey was conducted,\nconsidering flat, concave, and convex curvatures. The results indicated\nthat our haptic device can render diverse surface textures, such as\n“hairy” and “groovy”, on the fingertips\nthrough the control of applied pulse width modulated voltage signals.