top of page
Interaction Design | UX Research | Wearable 
How might we reduce mobility-related accidents experienced by people with visual impairment?

Design team of one; Advance Wearable Course

My Role

Research, Concept development, Prototype Design and Development (includes circuit construction & coding), Video Editing


April 2022, 3 weeks


Arduino Programming Language (C++), Arduino Uno, TENS unit (TENS 3000), Ultrasonic Sensor HC-SR04, Relay unit

Project Overview

This project targets on facilitating walking activity for users with vision impairment by incorporating TENS (transcutaneous electrical nerve stimulation) device as a form of haptics, to reduce mobility-related accidents.

Why it Matters

People with blindsight—the ability to detect things in the environment without being aware of seeing them, are faced with the obstacles of perform daily activities without bumping into erect objects or surfaces. They need to use a stick to track obstacles or require guidance by another person when walking around buildings. However, such dependency largely restricts the individual mobility of visually impaired person who often becomes more lonely, socially isolated, and with stronger feelings of worry, anxiety, and fear.

What is Vision Impairment?

According to WHO, globally, at least 2.2 billion people have a near or distance vision impairment by 2021.

  • Vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity;

  • In the absence of treatment, visual impairment may cause the individual difficulties with normal daily tasks including reading and walking.

What are the Challenges?

There are some designed adaptive equipment and spaces that can enable a blind/VI person to live their life independently but they are not always the case. VI community is still confronted with undeniable challenges and obstacles throughout daily activities. For example, some of the most prominent ones are listed below: 

Access to Information

Visual information that people need to perform daily activities: Timetables in train stations, signs, important notices and much more.

Space Navigation

The biggest challenge for a blind person, especially the one with the complete loss of vision, is to navigate around places.

Reduce Dependency

A VI person needs to put much effort to get each equipment that can take them one step closer towards independence.

Narrowing down the focus

Navigation: Spatial Recognition

VI/Blind people face with difficult recognizing depth in a space, which often adds up the dependency on other tools  or human/animal supports. 

What might happen?


Unintentional Injury: bumping and tripping


Sense of Disorientation


Decrease in Mobility & Independency
Family Trip
Current Coping Methods

Several techniques and methods can help people get around safely regardless of their amount of vision, and each with its own Pros and Cons:

The White Cane

Canes are relatively easy to replace and cost-efficient. 

However, canes are less "smart" and sometimes get stuck to the ground.

Guide Dogs

Guide dogs provide companionship and love, while keeping their handlers safe, but there are situations when dogs are not permitted or sick days.

Sighted Human

Similar to guided dogs, having a human companion is of great help but such companion may not always be available.

Assistive Tech

There are quite a handful of assistive technologies on the market, including handheld mobility aid and walking aids.

A Closer Examination
Screen Shot 2022-09-12 at 3.20.20 PM.png

Elmannai, Wafa, and Khaled Elleithy. 2017. "Sensor-Based Assistive Devices for Visually-Impaired People: Current Status, Challenges, and Future Directions" Sensors 17, no. 3: 565.

Listening to the User Group

As there are a handful coping methods with above identified problem with mobility-related activities, I decided to find target user group and ask about their individual perspective and needs. However, with limited time and resources, I was only able to secure two people (one classified as Moderate –visual acuity worse than 6/18 to 6/60 and another Severe –visual acuity worse than 6/60 to 3/60) willing to have a chat about their experiences. Out of confidentiality and ethnical concerns, their identity and personal information will not be disclosed. Each conversation lasted for approx. 15 minutes in a semi-structured interview format.

Key Insights
  • Ideal format of assistive technology

"Convenient and Light"
"Hand-held, or not hand held even better"
  • Functionality requirements

"Do not want to bump into walls"
"Head needs utmost attention of course"
"Have hearing issue, better if it's not audio guide"
  • Wearability concerns

"Small and not catching attention"
"Part of normal attire"
HMW Statement

How might we reduce mobility-related accidents for people with visual impairment?

  • How might we generate alerts that is neither visual nor audio based?

  • How might we include such assistive technology into daily attire with minimal obtrusiveness?

Solution: A Sensor-Based Assistive Device
Challenge 1

Generate alerts that is neither visual nor audio based for inclusive design purpose.

1. Haptic Feedback

Incorporating TENS (transcutaneous electrical nerve stimulation) device as a form of haptics. It is a form of electrical stimulus that oftentimes used in medical therapy. The small current generated is safe and creates a tingling sensation.

Challenge 2

Make a wearable technology that could be part of daily attire.

2. Proximity Sensor

I decided to incorporate Ultrasonic proximity sensor into a hat out of two considerations: 1). Prevention of head bumping by emitting signal from the head position; 2). Liberating the hands, which could be used to carry or hold other necessities.

Circuit Construction
Parts List
  • 1 Arduino UNO

  • 1 TENS unit (TENS 3000)

  • 1 Ultrasonic Sensor HC-SR04

  • 1 relay unit

  • 1 Felt hat

  • Breakout cables

  • 3 Male-to-Male jumper cables

  • 2 Male headers

  • Wire cutters/strippers

  • Sewing kit

  • Small slotted screwdriver

Circuit Diagram
Circuit diagram.png
Construction Process

I began the construction process immediately after the circuit diagram was completed. I started with testing the TENS machine and experimented with different level of pulse strength to find an appropriate range - able to feel the sensation while comfortable. After the basic circuit was tested successfully, I added other components - the proximity ultrasonic sensor and the hat!


As for the parameters of the ultrasonic sensor, it is set to 40 cm - meaning if the distance between the user and an obstacle is equal to or less than 40 centimetres meters, the TENS mechanism will be triggered and feeds back into the attached electrodes to create a mild sensation via sending electrical current at a safe and low voltage.

Final Product

For the last step, the complete circuit was revised and sewed into the interior of a handmade felt hat. Two holes were cut on the hat brim that is flipped up, making the room to place the ultrasonic sensor for signal emission and perception, which turns out to be bizarrely animated!

This hat serves as a Proof-of-Concept working prototype.

Video Documentation
Challenges & Success

Figuring out a way to incorporate TENS signal that is non-harmful yet effective on human bodies was one of the biggest challenges during the early stage of this project. As electrical muscle stimulation has a safe range of usage and a varied level of comfortableness upon users across different demographics, utilizing TENS needs thorough preliminary preparation and physiological backup. Out of the safety concern, I decided to proceed with a relatively safe and minimal side effect TENS device which has been clinically tested and commercially employed.

As this hat serves as a proof-of-concept working prototype, its final construction could be further improved by hiding the connection wires or making the prototype into two parts (communicating via bluetooth). For the current version user might find the wires hindering movement, but with a bluetooth connection such inconveniency shall be addressed.

Future Development

Furthering this project, I would like to experiment with analog vs. digital EMS/TENS signals. This piece of wearable could be further developed if it is able to measure bio-signals as inputs, adjust the output accordingly under Arduino programming. However, figuring the mode of connection and ensuring a safety range of pulse stimulation shall pose challenges.


Making the device "smarter" is worth exploring. Currently, there is a set threshold of distance which triggers the TENS stimulus, while it would be beneficial to map different strength of signal feedback adjusting to the distance adds on another layer of information. 

Lastly, incorporating EMS/TENS into creative practices along with other interactive technologies shall be interesting to be explored. It could potentially serve the same target user group with other functionalities such as indoor/outdoor navigation, information exchange, and alternative education with haptic feedback as an alternative language system.

bottom of page