Step 1 - Understanding the problem

The left arm was paralyzed from the shoulder to the wrist due to an illness called Acute flaccid myelitis (AFM). This illness caused spinal inflammation that subsequently damaged the nerves that transport the muscle signal from the brain to the muscles. This meant that there was no damage to the muscles themselves, however over time if they were not exercised they would atrophy. We still had movement in her wrist and fingers but there was less than 5% chance of a full recovery with traditional treatments.

We had an almost completely paralyzed shoulder, and over time the weight of her arm would pull the arm out of the socket. With a shoulder brace and Kenisio tape we could mitigate that and add a maximum of 150g on her arm. Therefore the Max weight of 150g was a key requirement.

Her bicep and triceps were the key muscle groups we wanted to focus on. In a zero gravity environment like when submerged in a pool, she was able to move her arm about 10 degrees unassisted. That meant there was a signal going to her muscles. We wanted to pick up these signals and use those to control the assistive device, therefore fostering the use of her muscles and increasing the chances of recovery.

Her forearm weighs about 400g, therefore whatever we did, needed to be able to pick up at least that weight. It would need to be mobile, operate for hours on end, be easily adaptable, beautiful, and easy to use.

Looking at our requirements, we decided to build our own device. It would include a custom fitted arm brace, an actuator or pully mechanism and embedded sensors. At this stage, do some research. Look at all possible solutions to solving your particular requirements, it may be that this assistive arm is not the best option for you.

For reference, we recorded much of our research here.