Modulus-Adjustable Smart Insole with Magneto-tunable Flexibility, High Impact-Responsive Energy Absorption and Low-Voltage Thermal Management

Foot-mounted wearable equipment is rapidly being applied in healthcare and sports protection. However, it still faces limitations such as un-tunable mechanical properties, insufficient impact cushioning, and single functionality, failing to meet the personalized dynamic requirements. Herein, a magnetorheological-shear stiffening synergistic conductive composite fabric (named MRG/MFC) is proposed for smart insoles, integrating magneto-tunable flexibility, efficient impact cushioning, and electrothermal therapy. Under applying the magnetic field, the modulus of MRG/MFC can be adjusted and the magnetorheological effect of the magnetorheological shear stiffening gel (MRG) reaches up to 3161% (600 mT). Meanwhile, the shear stiffening gel endows the MRG/MFC with the typical rate-dependent energy dissipation, in which the peak impact force can be critically reduced (>45%) and the buffer time can be particularly prolonged (>80%). In addition, MRG/MFC can quickly absorb sweat; thus, it also enhances the wearing comfort. Furthermore, owing to the good electric conductivity, the MRG/MFC shows wonderful electrothermal properties (30–115 °C) under low voltage, and this offers the possibility for foot health care. Finally, a smart insole integrated with MRG/MFC is constructed and its plantar stress distribution can be regulated via attaching a magnetic sticker. As a result, this design concept provides a multifunctional composite for personalized foot protection which possesses wide application potential for athletes and diabetic patients.