Band attachment prototype
Overview of context, design process, and outcome
Overview of context, design process, and outcome
Render of final concept
Testing of interaction prototype
Testing of band attachment prototypes
Exploded view of band attachment
What it does
Although the ability of men with Duchenne Muscular Dystrophy to move their muscles reduces over time, their EMG signal remains. Myonics measures and processes this EMG signal and translates it into cursor movement and clicking.
Duchenne Muscular Dystrophy (DMD) is a progressive neuromuscular disease that mainly affects males. It is one of the most common hereditary diseases and occurs in about 1 in every 3500 boys worldwide. Recently, the average life expectancy has increased from teens to 30s. They are now able to attend college and start careers, where using a computer is essential. However, when these men enter into the late non-ambulatory stage of DMD, they are no longer able to move their arms or hands. TU Delft was approached by Yumen Bionics and Duchenne Parent Project to develop a device that allows these men to operate their computers using EMG signals.
How it works
A myonics band is placed on each arm. The band adjusts to users with different arm shapes and sizes, due to its elastic and segmented structure. There is an inner layer of foam that allows the device to be worn comfortably for long periods of time. Even though users are unable to physically move their arms, their intent to do so is still translated into contraction of the corresponding muscles. This EMG signal is sensed using a series of eight EMG electrodes embedded into each band. Engaging the bicep and triceps on the left arm controls the cursor movements in the horizontal direction. The bicep and triceps on the right arm control the cursor movement in the vertical direction. The left and right clicks are controlled by the extensor digitorum muscle in the respective forearms. The triceps tendon acts as a ground. The extent to which the user flexes their muscles controls the speed of the cursor in the corresponding directions.
The development of the device was divided into three main subsystems: electronics, software, and band attachment. In order to develop and test these subsystems, two types of prototypes were created: band attachment and interaction. The band attachment was designed through a trial-and-error approach and extensive testing. First, through literature research, testing, and a program of requirements, the muscles in which the EMG sensors were to be placed were selected. Then, four series of prototypes were developed, with each design iteration having focus areas. These areas include ergonomics, pressure sensitivity, product experience, electronics integration, material testing, attachment and placement, cleaning, and not interfering with existing equipment. The needs and wants of caregivers were also taken into consideration, as they will be attaching the device and cleaning it. The interaction prototypes incorporated the software and electronics subsystems. Through dozens of iterations, signal processing was developed to accurately interpret the intent of the user from the EMG signal and translate it into cursor movement. In doing so, the envelope, deadzone, range, and mapping of the EMG signals were defined, as well as how to calibrate the device to each user’s signal strength.
How it is different
Men with Duchenne Muscular Dystrophy have needs not met by the EMG wearables currently on the market. Due to muscle deterioration, their EMG signal strength is significantly less than a person with full muscle function and they lack muscle definition. Their arms cannot be extended to put on the device since doing so could lead to damaging tendons. The user will be sitting stationary in a wheelchair, rather than up and moving, as the use case of most EMG wearables. In addition, a caregiver will be attaching and maintaining the device, not the user. As the user has numerous caregivers, attaching and correctly placing the band must be intuitive. Incorporating these differences, and dozens more, into the development of myonics, we were able to create a unique product that is customized for men with DMD.
The device will be further developed and optimized by Yumen Bionics. These development plans include merging the band attachment and interaction prototypes into one device. With this comes integrating a dongle Bluetooth connection and adding an application with a Graphical User Interface to further customize the device to each user’s EMG signal strength. Further testing is to be conducted with men with DMD to determine the range of signal strengths and the most effective muscle movements to complete each cursor action. When the final solution is complete, men with DMD will be able to operate their computers seamlessly.