Michał Kamiński

Rapid growth of personal electronics with concurrent research into telerehabilitation solutions discovers opportunities to redefine the future of orthopedic rehabilitation. After joint injury or operation, convalescence includes free active range of movement exercises, such as joints bending and straightening under medical supervision. Flexion detection through wearable textile sensors provides numerous potential benefits such as: (1) reduced cost; (2) continuous monitoring; (3) remote telerehabilitation; (4) gamification; and (5) detection of risk-inducing activities in daily routine. To address this issue, novel piezoresistive multi-walled carbon nanotubes/graphite/styrene–butadiene–styrene copolymer (CNT/Gr/SBS) fiber was developed. The extrusion process allowed adjustable diameter fiber production, while being a scalable, industrially adapted method of manufacturing textile electronics. Composite fibers were highly stretchable, withstanding strains up to 285%, and exhibited exceptional piezoresistive parameters with a gauge factor of 91.64 for 0–100% strain range and 2955 for the full scope. Considering the composite’s flexibility and sensitivity during a series of cyclic loading, it was concluded that developed Gr/CNT/SBS fibers were suitable for application in wearable piezoresistive sensors for telerehabilitation application.

The following paper presents a simple, low-cost, and repeatable manufacturing process for fabricating conductive, elastic carbon-elastomer nanocomposite fibers for applications in the textile industry and beyond. The presented method allows for the manufacturing of fibers with a diameter of 0.2 mm, containing up to 50 vol. % of graphite powder, 10 vol. % of CNT, and a mix of both fillers. As a result, resistivity below 0.2 Ωm for the 0.2 mm-diameter fibers was achieved. Additionally, conductive fibers are highly elastic, which makes them suitable for use in the textile industry as an element of circuits. The effect of strain on the change in resistance was also tested. Researches have shown that highly conductive fibers can withstand strain of up to 40%, with resistivity increasing nearly five times compared to the unstretched fiber. This research shows that the developed composites can also be used as strain sensors in textronic systems. Finally, functional demonstrators were made by directly sewing the developed fibers into a cotton fabric. First, the non-quantitative tests indicate the feasibility of using the composites as conductive fibers to power components in textronic systems and for bending detection.