Soft Robotic Exoskeleton for Cerebral Palsy Rehabilitation

Abstract

Purpose: This work presents development of a soft robotic exoskeleton to provide active and passive therapeutic-assistive hand motion for children between the ages of 5-12 suffering from Cerebral Palsy (CP) while recording and adapting to the current state of the hand. Cerebral Palsy is a birth related brain injury; studies have shown that 60-83% of children with CP have some form of upper extremity limitations that lead to reduced hand functions and quality of life. Soft robotic devices show promise as a therapy extender needed for motor learning while reducing the safety issues involved in conventional robotic systems. The developed soft exoskeleton is integrated with sensors that measure finger trajectory (inertial measurement units) and force (in-line pressure) associated with finger extension and flexion. Finger trajectory and associated forces will provide a quantifiable means for tracking therapy progression. Methods: The robotic exoskeleton includes five hybrid soft-and-rigid robotic digits attached on top of a wearable attachment. The soft robotic digits was designed based on the measurements from 16 children’s hands (7 girls and 9 boys in the range of 5-12 years old) to fit the children's range of hand sizes while it satisfies the kinematic compatibility with finger joint range-of-motion and center-of-rotation. The robotic digit is comprised of three inflatable bellow-shaped structure sections and four semi-rigid sections in an alternating order which correspond to the anatomy of a human finger. Fabricated with 3D printed injection molds and over molding techniques, the soft robotic digits were made using silicone rubber material. The robot is actuated using pressurized air, where it was successfully tested so that it can provide full range of motion with inflation pressure of 200 kPa. Results: Soft robotic exoskeletons in a small, medium and large size has been developed by assembling the robotic digits into the wearable attachment. Initial feasibility testing have been carried out on one healthy child (a 6 years old boy with medium hand size) to evaluate the operation, ease-of-use, and level of comfort provided by the robot. Results from the preliminary test and the feedback from the subject through the questionnaire indicated the ease-of-use, safety, and effective operation of the robot. Conclusions: We plan to extend this pilot study to CP patients to evaluate the effectiveness of the soft robotic exoskeleton on this population.