PCB-based miniature vibro-tactile display for the visually impaired

Abstract

An estimated 2.2 billion people worldwide are visually impaired (WHO, 2019), yet current Braille readers are limited to one or two rows of text and cannot display images. Thus, a low-cost, electronically refreshable tactile display for accessing graphical and textual information is needed. We are developing such a display using a printed circuit board (PCB) as the substrate and bottom electrode array, and a metalized Kapton film as the vibrating membrane. Punched foam tape is used as a spacer to create a gap between the board and film so the pixels can be actuated electrostatically. The current prototype has 6 pixels at 3.5 mm spacing, Vibration amplitudes of 8 microns peak-to-peak were achieved in a prototype using a drive voltage of 600V at 200 Hz. This is sensible to the human touch. Further optimization requires matching the mechanical impedance of the finger, and maximizing vibration amplitude in the preferred sensible frequency range between 50 and 300 Hz. Finite element analysis (FEA), laser vibrometry, and nano-newton force-displacement measurements have been used to characterize the system. Future versions will increase amplitude, reduce drive voltages, and increase display resolution to larger arrays of more closely spaced pixels through further miniaturization.