Comparison of the Capacitance of a Cyclically Fatigued Stretch Sensor to a Non-Fatigued Stretch Sensor When Performing Static and Dynamic Foot-Ankle Motions

• Published in: Sensors (Basel, Switzerland) Vol. 22; no. 21; p. 8168
• Main Authors: Persons, Andrea Karen, Middleton, Carver, Parker, Erin, Carroll, Will, Turner, Alana, Talegaonkar, Purva, Davarzani, Samaneh, Saucier, David, Chander, Harish, Ball, John E, Elder, Steven H, Simpson, Chartrisa LaShan, Macias, David, Burch V, Reuben F
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 25.10.2022; MDPI
• Subjects: Analysis; Ankle; Ankle Joint; Basketball; Biomechanical Phenomena; Biomechanics; Capacitance; cyclic softening; drift; Durability; Fatigue tests; Gait; High cycle fatigue; Human motion; Humans; Laboratories; Motion; Motion capture; Movement; Orthopedics; Sensors; Smart sensors; stretch sensor; capacitance; stretch sensor; ankle joint; high-cycle fatigue; cyclic softening; drift; smart sock
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s22218168

Motion capture is the current gold standard for assessing movement of the human body, but laboratory settings do not always mimic the natural terrains and movements encountered by humans. To overcome such limitations, a smart sock that is equipped with stretch sensors is being developed to record movement data outside of the laboratory. For the smart sock stretch sensors to provide valuable feedback, the sensors should have durability of both materials and signal. To test the durability of the stretch sensors, the sensors were exposed to high-cycle fatigue testing with simultaneous capture of the capacitance. Following randomization, either the fatigued sensor or an unfatigued sensor was placed in the plantarflexion position on the smart sock, and participants were asked to complete the following static movements: dorsiflexion, inversion, eversion, and plantarflexion. Participants were then asked to complete gait trials. The sensor was then exchanged for either an unfatigued or fatigued plantarflexion sensor, depending upon which sensor the trials began with, and each trial was repeated by the participant using the opposite sensor. Results of the tests show that for both the static and dynamic movements, the capacitive output of the fatigued sensor was consistently higher than that of the unfatigued sensor suggesting that an upwards drift of the capacitance was occurring in the fatigued sensors. More research is needed to determine whether stretch sensors should be pre-stretched prior to data collection, and to also determine whether the drift stabilizes once the cyclic softening of the materials comprising the sensor has stabilized.