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Quantitative measurements of human movements can drastically change how coaches, trainers, and clinicians tailor physical training, teach new athletic skills, and prescribe treatment for musculoskeletal injuries, such as ankle sprains. The gold standard for movement characterization today is optical motion capture, which uses an array of fixed high-resolution cameras to track markers mounted on a moving body. However, optical motion capture is inconvenient outside a laboratory and susceptible to movement artifacts such as skin and clothing/shoe deformation. Thus, this study aimed to develop a field-deployable, skin-mounted, skin-strain sensor that can accurately quantify skin strains while measuring muscular engagement during functional movements. The approach was to directly integrate piezoresistive graphene nanocomposites with commercial kinesiology tape to form a self-adhesive skin-strain sensor that could be mounted virtually anywhere on the body, such as the ankle-foot complex. Unlike optical motion capture and electronic textiles, “Motion Tape” can be worn underneath garments and within the shoe, directly measure skin-strains, and are insensitive to movement artifacts. This work began with fabricating Motion Tape using a scalable spray-coating method. The cyclic strain sensing properties were characterized through extensive load frame tests. Then, controlled experiments using test coupons and human studies were performed to compare the Motion Tape sensing response versus optical motion capture during a series of representative movements. Besides showing comparable sensing results, densely distributed skin-strain monitoring using Motion Tape was demonstrated using an electrical impedance tomography measurement strategy and algorithm. The distributed strains induced during dorsiflexion and plantarflexion of the ankle-foot complex were successfully characterized.
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