Vibro-tactile display for the visually impaired using miniature electrostatic transducers

Abstract

A vibro-tactile electronic display is being developed to aid the visually impaired community by increasing access to graphical and textual information. A high-density vibro-tactile arrayed display would improve the user experience while moving away from external displays on the market. We propose to use millimeter scale electrostatic transducers operating at frequencies well below resonance as candidate array pixel elements. Motion detectable by a fingertip, mechanical impedance of a fingertip, and frequency at which fingertips can detect contact were considered. Motion of 5μm with a fingertip touching the device and 10 μm without a finger touching the device is desired with the device at a mechanical impedance of 480N/m, which is twice the mechanical impedance of the fingertip (240N/m measured by Diller and Kyung). Transducer membrane thickness, force on the fingertip, and gap width are being optimized through prototyping and finite element analysis. A prototyped row of pixels was manufactured using 0.051 mm thick metalized Mylar film with an air gap of 0.02mm and a diameter of 1 to 2 mm per pixel, driven by AC electrostatics at 400 V peak to peak. Motion analysis is being conducted using a laser vibrometer. Preliminary results demonstrate motion of 10 μm peak to peak at low frequencies, with further analysis and optimization ongoing.