Stretchable helical fiber sensor with human motion monitoring capability for mandibular motion assessment in temporomandibular disorders

Temporomandibular disorders (TMDs) are prevalent musculoskeletal conditions affecting the orofacial region. Wearable monitoring of mandibular motion may facilitate clinical assessment of TMDs. To satisfy this critical demand, this work proposes a highly stretchable and sensitive sensing strategy via the integration of a graphite nanosheet conductive ink with flexible fibers featuring a unique helical architecture, enabling the construction of a stretchable helical fiber sensor (HFS). The effective integration between the conductive layer and the fiber substrate was confirmed by microscopic morphological characterization. Performance evaluations demonstrated that the HFS possesses a low strain-detection limit of 0.5%, a rapid response time of 33 ms, and excellent stability over 10,000 deformation cycles. In practical demonstrations, the HFS recorded different motion-related signals from blinking to jumping and mandibular-motion-related strain signals in three illustrative cases (one with bilaterally normal temporomandibular joints and two with unilateral disc displacement with reduction). These findings support the preliminary feasibility of the HFS as a wearable tool for the adjunctive assessment of TMD-related mandibular motion, although validation in larger cohorts using established reference methods is required.