Development of a magnetic composite material for measurement of residual limb displacements in prosthetic sockets. (March 2018)

• Record Type: Journal Article
• Authors: Weathersby, Ethan J; Cagle, John C; Larsen, Brian G; Henrikson, Katrina M; Sanders, Joan E
• Is Part Of: Journal of rehabilitation and assistive technologies engineering. Volume 5(2018)
• Publication Date: 2018-03
• Subjects: Amputees -- biomechanical testing/analysis -- limb prosthetics -- rehabilitation -- sensor design; Rehabilitation technology -- Periodicals; 617.03
• DOI: 10.1177/2055668318763481
• Languages: English
• ISSNs: 2055-6683

Abstract

Introduction: Wearable limb–socket displacement sensors may help patients and prosthetists identify a deteriorating socket fit and justify the need for repair or replacement. Methods: A novel sensor using an inductive sensing modality was developed to detect limb-to-socket distances. Key detection elements were a coil antenna placed in the socket wall and a magnetic composite sheath worn over the outside of the prosthesis user's elastomeric liner. The sheath was a nylon or cotton prosthetic stocking coated with a polyurethane composite. The polyurethane composite contained embedded iron particles (75 wt%). Results: Brushing γ-glycidoxypropyltriethoxysilane onto the sheath fabric, coating it first with unfilled polyurethane and then iron-filled polyurethane, enhanced bonding between the sheath and the composite and overcame mechanical degradation problems. A γ-glycidoxypropyltriethoxysilane-rich fumed silica layer applied to the outside of the sheath reduced friction and improved durability. Field testing demonstrated less than a 3% signal degradation from four weeks of field use. Conclusions: The developed wearable displacement sensor meets durability and performance needs, and is ready for large-scale clinical testing.