Pneumatically Actuated Soft Wearable Exoskeleton for Upper Limb Motion Rehabilitation; Exploring the Effects of Realism and Demographic Factors on Prosthetic Interaction in Amputees

Great engineering doesn’t stop at solving a problem - it considers how that solution will be lived with and embraced by the people it is designed to help. This is especially fitting in the field of wearable technology, particularly wearable exoskeletons and prosthetics. My capstone project this year proposes a new design for a wearable soft upper limb exoskeleton that assists with shoulder motion. Its purpose is to help users regain motion lost due to injury or stroke through a portable, lightweight device that can be used in the comfort of one’s own home. My STS research focuses on the effects of device realism and user demographics on user satisfaction in amputees. The purpose of this research is to understand what external factors might be influencing human-prosthetic interaction and use this information to guide engineers and prosthetists in future prosthetic design. Both my capstone project and my STS paper focus on wearable technologies that restore motion in some way. Together, these projects reflect a shared goal: to design wearable devices that are not only highly functional, but also aligned with the diverse needs and interests of their users.

The motivation behind our capstone stems from the growing need for portable, at-home rehabilitation solutions for individuals with restricted shoulder motion. Physical therapy can be expensive and time-consuming, making it inaccessible for some patients. Our team sought to address this gap by designing a wearable exoskeleton that is affordable, lightweight, portable, and easy to use at home. The device can be separated into three core subsystems: mechanical structure, actuation, and control. Computer-aided design (CAD) and 3D printing were used for the mechanical structure, including the shoulder collar and the hinge mechanism used to hold the pneumatic muscles. Two pneumatic muscles, constructed from rubber tubing encased in mesh, provide the actuation necessary for restoring arm motion. The control subsystem focuses on automating inflation and deflation using a solenoid valve and electrical components, eliminating the need for manual operation.

In conclusion, the exoskeleton is capable of achieving approximately 80 degrees of shoulder abduction and roughly 40 degrees of flexion when the user begins with their arm at rest. After reaching the target range of motion (ROM), the device can slowly deflate to return the arm to its original resting position, and this cycle can be repeated multiple times. The exoskeleton supports both abduction/adduction and flexion/extension due to a modular, snap-fit design on the shoulder collar. This feature allows the hinge mechanism to be repositioned, enabling directional changes in arm movement. However, we encountered technical challenges - particularly in executing flexion and extension. Because pneumatic muscles primarily provide linear actuation, they are well-suited for generating the necessary forces for single degree-of-freedom (DOF) movements, but are less effective for achieving multiple DOF unless multiple muscles are used and arranged to control different planes of movement. The structural layout includes one muscle connecting from a forearm brace to the top of the shoulder, and a second muscle extending across the back to the opposite shoulder. During flexion and extension trials, rotating the hinge caused the back muscle to twist in an unnatural way. As a result, we used only the primary muscle during this motion, which limited the achievable ROM in flexion.

My STS thesis investigates how device realism and user demographics influence user satisfaction in amputees. Millions of Americans are living with limb loss. Because of this, they struggle with performing seemingly simple tasks each day. Oftentimes, this leads to emotional distress and a lower quality of life. Understanding the factors that shape prosthetic satisfaction is therefore essential to designing devices that serve diverse populations effectively. Engineers, scientists, and prosthetists have a responsibility to use this knowledge to improve prosthetic design and enhance user experience. To explore this topic, I performed a literature review that examined surveys, questionnaires, and case studies related to prosthetic use and satisfaction. I then applied the Actor-Network Theory (ANT) to analyze the complex network of human and nonhuman actors that influence the way individuals think about and interact with their devices.

My research found that user satisfaction in prosthetics is shaped by more than just mechanical performance - it is also influenced by factors such as time since amputation, realism, aesthetics, age, and gender. Surveys and questionnaires across the literature revealed key trends in how these factors interact. For instance, some research shows that users may be more satisfied using cosmetic devices initially following limb loss to maintain a sense of normalcy. Over time, they become more comfortable using less aesthetic, functional devices as they have had time adjusting to the loss. The studies also showed deviations between men and women, with women reporting a higher preference for cosmetic devices than men. Younger individuals tended to report higher dissatisfaction with their devices, while the role race plays in user satisfaction remains unclear. Overall, this research highlighted several impactful patterns linking prosthetic realism and user demographics to satisfaction. However, there is still a substantial need for future research to be conducted using larger, more diverse sample sizes.

School of Engineering and Applied Science

Bachelor of Science in Mechanical Engineering

Technical Advisor: Sarah Sun

STS Advisor: Pedro Augusto Francisco

Technical Team Members: Jahnavi Dave, Joshua Lim, Jake Morrisey, Jackson Spain, Courtney Wilks