Abstract
Ischemic stroke is a deadly and debilitating medical event that leaves many people with motor disfunction. Post-stroke loss of hand functionality can be restored through powered hand orthosis. Artificial muscles like coiled shape memory alloy (SMA) can provide the necessary tension and pulling force needed to assist with flexion of the digits. Coiled SMA muscles have been implemented in several orthotic devices. One of the greatest obstacles in powered orthotic design is affordability. Leveraging inexpensive manufacturing processes like 3D printing can greatly minimize production and consumer cost and help customization. This would greatly bridge the price gap that exists between passive orthoses and smart feedback-controlled orthoses.
This work proposes an electrically powered single finger soft orthosis with embedded strain gauge made through a single step 3D printing approach. We utilized inexpensive coiled nickel titanium SMA muscles to assist in flexion of the index finger. Using an embedded strain gauge made from conductive thermoplastic polyurethane (CTPU), we can accurately monitor the flexion angle of the index finger. This precise data can be paired with electromyography (EMG) control to produce feedback-controlled movement. The expected fabrication cost of this orthotic finger is below $750, making it much cheaper than other smart powered orthoses currently available. We will show how the device responds to cyclic use under different input parameters. Using these responses, we will develop strategies to leverage the performance of the device for a variety of activities of daily life.
