Embedded Files
Overview
Product: Shoulder Hiking Detection Rehabilitation Device
Project Goal: Design a device to assist individuals recovering from a stroke or rotator cuff injury by detecting improper shoulder movement
Responsibilities:
Conducted research on medical conditions and existing patents
Lead product development from concept to production ready
Built and iterated functional prototypes
Designed and executed product testing protocols
Project Challenges:
Innovating a device with no existing solutions
Development Schedules
Development cycles began in 2014 at the ReWIRE Lab during my undergraduate studies. Progress was intentionally paced due to limited weekly availability. Further development did not begin again until Spring 2016 where potential for commercialization was a viable option.
What is Shoulder Hiking or Shrug Sign?
Shoulder hiking, also known as the shrug sign, is commonly observed in individuals recovering from a torn rotator cuff and, less frequently, in stroke survivors. It refers to the inability to abduct the arm to 90° without compensatory elevation of the scapula or shoulder girdle. If left unaddressed, this compensatory movement can lead to additional physical complications over time.
Product Criteria
Have different levels of sensitivity
Have physical feedback
Must have auditory feedback
No electronics
Promotes independence from technicians
Must produce feedback in the z-axis
Simple
Affordable
Early Development
IR Sensor Exploration
Proved to be rather tricky to orient on a person's body for effective alerting and partnered doctors remained firm on no electronics.
Flexure Bar Exploration
The flexure bar offered a simple, electronics-free solution that provided haptic feedback to the user. However, it had several limitations:
Needed to be custom-made for each user
Risk of deformation if overloaded due to relief cuts
Lacked audio feedback
Audio feedback was considered the most critical component by the partnering doctors, as it provided a clear and immediate alert to the user when shoulder shrugging occurred. Haptic feedback alone was not deemed sufficient - especially given that the device was intended for daily use, where reliable and noticeable feedback would be essential for forming new movement habits.
Measuring Tape Exploration
media1.MOVThis early functional prototype addressed nearly all product criteria, except for adjustable sensitivity levels. It borrowed core components from the flexure bar concept but replaced the relief cut design with a measuring tape section. The measuring tape served a dual purpose: it alerted the user when their shoulder moved out of position and when the shoulder return back into proper alignment.
media2.MOV
Design for Manufacturing
The following design for manufacturing work was developed at a later stage, outside of the original lab setting, as I explored commercialization opportunities through a startup venture.
3D Printing Design
The overall design is intentionally simple. The 3D printed plastic end pieces house all the essential hardware components, including:
snap button
threaded insert
fastener
metal strip
Loose tolerances were acceptable for the printed parts, as the snap buttons were secured with adhesive rather than relying on a tight press fit. The metal strip was cut to length and offered in three standardized sizes to accommodate different users.
Injection Molding Design
The injection molded version closely mirrors the 3D printed prototype but is optimized for mass production. Key improvements include the use of insert molding to accommodate the threaded insert and snap button to minimize assembly time.
The part was also refined to minimize material waste and eliminate thick wall sections, ensuring more consistent cooling, reduced cycle times, and improved structural performance.
Product Evaluation Testing
The evaluation study involved 30 healthy participants, each performing two rounds of alternating arm exercises. The first round was done without weights to establish a baseline, followed by a second round using an appropriate weight for each individual.
LED motion capture markers were placed on the following anatomical points:
Scapula
Device
Upper arm
AC joint
Sternum
After data collection, the recordings were scrubbed and analyzed. The chart on the right displays a sample of the results, showing a clear instance of a shoulder shrug during a single repetition. The mic data indicates when the device activated in response to excessive scapular elevation, followed by the user's correction.
Results showed that the device reliably triggered at approximately 3mm of scapular height deviation from baseline, with minimal false positives.
Lessons Learned
Key Takeaways
Gained firsthand experience in product development from an academic perspective
Explored iterative design processes, ranging from electronic to purely mechanical solutions
Built foundational skills in evaluating and analyzing product functionality
Improvements
Shorten development cycle through better project planning and time allocation
Explore a "one-size-fits-all" solution to improve usability and scalability
Take a more active role in data analysis and interpretation for deeper insights
Google Sites
Report abuse