Research

I didn’t have prior experience designing for visual disabilities, so I met with the Associate Director of the Vista Center for the Blind and Visually Impaired in Palo Alto to understand how people with varying degrees of vision impairment navigate technology. At the time, most existing payment terminals still used physical keypads, and vision impaired users relied on a raised bump on the “5” key to orient themselves. Touchscreens lacked these built-in affordances.After evaluating a range of approaches—from haptic feedback + gesture input to audio-based solutions—I ruled out many options due to feasibility, cost, security concerns, or hardware incompatibility. For example, external pin pads were too costly for buyers and headphone jacks posed privacy and technical issues. We also could not cover any part of the touchscreen with tactile overlays.

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Physical + Digital Prototyping

I began prototyping tactile overlays by hand using cardboard and PVC foam. The idea was to design a tactile frame that could sit on top of the screen without obstructing touch functionality. I paired this with a custom digital PIN entry interface that matched the frame layout, so users could feel for a number, slide their finger in, and double tap to confirm their choice. I initially designed the interface with numbers arranged in a circular pattern to minimize screen contact, but early feedback revealed that users expected a left-to-right, top-to-bottom flow—so I revised the layout accordingly.

To explore materials and iterate quickly, I visited local craft stores and experimented with thermoplastics. I built mid-fidelity prototypes using PVC foam, which could be cut and reshaped with heat. When I needed a more durable, testable model, I taught myself SketchUp, modeled the frame in 3D, and partnered with a local makerspace to 3D print the prototype.

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Usability Testing

I returned to the Vista Center to test the solution with one blind and one low-vision participant, both over the age of 50. From these sessions, I gained critical insights. The blind participant responded well to the tactile interface and suggested reordering the number layout to read naturally across rows. The low vision participant, however, struggled with the new interface and said he preferred the traditional keypad layout—just with more visual clarity and contrast. Based on this feedback, I designed a separate high-contrast version of the traditional PIN interface, with bold text, color cues, and a highlighted “5” key to aid orientation.

Solution

The final design consisted of two complementary solutions: a tactile frame with Braille markers aligned to a custom PIN interface for blind users, and an enhanced high-contrast version of the existing keypad layout for low vision users. The tactile solution allowed users to enter their PIN through guided touch and double-tap input, while the visual solution prioritized clarity, contrast, and familiarity.The design was secure, intuitive, and required no significant modification to the touchscreen hardware—making it scalable and cost-effective to implement. It was reviewed and approved by internal stakeholders and accessibility experts, and prepared for manufacturing and rollout.

The accessibility solution was submitted for a patent and approved for production. It was implemented across 50,000 Poynt terminals deployed in Brazil.

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