Designing a Low-cost Finger Wearable Audio-tactile Device
Arshad Nasser · 2019 · Proceedings of the 21st International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS 2019) · doi:10.1145/3308561.3356105
Summary
This student research abstract describes the iterative design of ColorTact, a finger-worn wearable device that provides audio annotations when users explore tactile diagrams. The device addresses a fundamental limitation of conventional tactile graphics: they can only accommodate a finite number of annotations and braille labels on a single page, forcing users to flip between multiple pages to access descriptive content. ColorTact works by using a color sensor mounted on the fingertip to detect discrete color-tagged areas on tactile diagrams, triggering corresponding pre-recorded audio output stored in a color-to-audio mapping profile. The key advantage over existing approaches — such as touchscreen overlays, camera-based hand tracking, or QR codes — is that ColorTact leaves both hands free for tactile exploration without occupying one hand or requiring complex image processing. The device went through three iterative prototypes developed with input from eight visually impaired participants recruited from the Hong Kong Blind Union and Ebenezer School for Blind. The design evolved from a computer-tethered finger device to a standalone wearable with all hardware (Arduino Nano, Bluetooth module, battery, color sensor) housed in a single unit worn across the finger and wrist.
Key findings
The iterative user-centred design process revealed several important insights about wearable assistive device design. The first prototype, which required pressing a button on the proximal phalanx while pointing at colored areas, proved awkward — three of four participants found it difficult to simultaneously point and press. Wires connecting the finger device to a computer were reported as cumbersome. The second prototype moved the electronics to a wrist-worn unit connected wirelessly via Bluetooth and angled the color sensor at 45 degrees to prevent it from obstructing tactile exploration. The final prototype introduced a "point and tilt to click" interaction method using a limit switch at the fingertip, providing tactile feedback on activation while eliminating the awkward button press. RFID tags were added to allow color profile reuse across multiple tactile diagram pages — hovering over the top-left corner of a page automatically loads the correct audio mapping. A companion Android app built with MIT AppInventor allows users to create and manage color-to-audio profiles. The total hardware cost for the final prototype was under 25 USD. Subjective user feedback was positive regarding the ergonomic design, weight, cost, and ease of setup.
Relevance
ColorTact demonstrates how low-cost, open-source hardware (Arduino) and iterative participatory design can produce practical assistive technology for tactile graphics access. For accessibility practitioners working in education — particularly STEM fields where diagrams are essential — this approach offers a complement to existing solutions like the Talking Tactile Pen. The under-25-USD cost makes it viable for schools and organisations in resource-constrained settings, and the use of colored stickers or prints for tagging means existing tactile materials can be augmented without specialised production equipment. The design lessons around fingertip ergonomics and interaction methods are valuable for anyone developing finger-worn assistive devices. However, as a student research abstract, this is a preliminary proof of concept — it lacks formal evaluation metrics, has been tested with only small groups, and the color-sensing approach has inherent limitations with color detection reliability and the number of distinct colors that can be used on a single diagram.
Tags: assistive technology · tactile graphics · wearable technology · audio description · visual impairment · DIY assistive technology · Arduino · low-cost accessibility · STEM accessibility