Theoretical Foundations and Experimental Investigation of Electroactive Polymer Artificial Muscles for Soft Exoskeleton Devices Targeting Stroke Rehabilitation in Nigerian Teaching Hospitals

Stroke is among the leading causes of adult disability in Nigeria, with post-stroke upper limb motor impairment affecting a substantial proportion of the estimated 500,000 annual stroke survivors, yet soft robotic exoskeleton devices for upper limb rehabilitation that are affordable, lightweight, and comfortable for long-duration therapeutic use remain inaccessible within the Nigerian healthcare system. Dielectric elastomer actuator-based electroactive polymer artificial muscles represent a promising technology for soft exoskeleton joint actuation due to their high power-to-weight ratio, silent operation, and mechanical compliance, yet their application to wearable rehabilitation exoskeletons is constrained by incomplete theoretical understanding of their electromechanical behaviour under the complex loading conditions of exoskeleton joint actuation and limited experimental characterization at physiologically relevant actuation frequencies. This dissertation develops theoretical foundations and conducts experimental investigation of DEA artificial muscles for soft exoskeleton applications targeting stroke hand rehabilitation. A large-deformation electromechanical constitutive theory for DEA membranes under multi-axial loading is developed incorporating viscoelastic material behaviour at physiological frequencies from 0.1 to 5 Hz, with model parameters identified from a comprehensive experimental characterization campaign. An antagonistic DEA actuator module is designed and fabricated, and a model-based control framework for joint angle and impedance regulation is derived from the constitutive theory. Clinical evaluation of a prototype DEA-actuated exoskeleton glove is conducted with 18 stroke patients recruited from the National Hospital Abuja neurology ward, demonstrating statistically significant improvement in grip strength and Fugl-Meyer upper extremity scores relative to conventional physiotherapy over an eight-week intervention. Keywords: electroactive polymer, artificial muscle, soft exoskeleton, stroke rehabilitation, Nigerian hospital