PCB-Based Miniature Vibro-Tactile Display for the Visually Impaired

Abstract

Current Braille readers are costly, limited to one or two rows of text, and there are no affordable tactile displays for images. To address this, we have developed a low-cost, electronically refreshable vibrotactile display prototype inspired by capacitive micromachined ultrasound transducers (CMUT). The design utilizes a printed circuit board (PCB) as the substrate and bottom electrode array, combined with a metalized Kapton film as the vibrating membrane and punched foam tape as a spacer. The current prototype demonstrates a 2x3 array of tactels (a tactile pixel) with 3.0 mm spacing. The system was modeled using finite element analysis (FEA) and characterized using laser vibrometry. Vibration amplitudes of 1.0 μm to 7.0 μm peak-to-peak were achieved using a peak-to-peak drive voltage of 600V at 200 to 300 Hz. Distinct patterns in the shape of Braille characters have been generated. A human subject study was conducted with 10 unskilled participants each conducting 20 trials on a discrimination task. Eight of the ten participants achieved an accuracy greater than 70% indicating that the patterns can be discriminated (N = 200, p = 0.0027). The prototype demonstrates the feasibility of this approach and is scalable to large area displays at low cost.