Flexible dual-mode epidermal sensor for time-sharing muscle fatigue monitoring and photothermal therapy

Traditional muscle fatigue detection methods are cumbersome and signal analysis is complex, which makes it challenging to monitor and treat muscle fatigue in real-time. Here, we developed a flexible dual-mode epidermal sensor for force detection and photothermal therapy by decorating elastic and porous substrates (polydimethylsiloxane polyurethane [PDMS]) with homogenous and robust conductive networks. Multiwalled carbon nanotubes (MWCNTs) were grafted onto hydroxypropyl cellulose (HPC) surfaces via polydopamine (PDA). With the assistance of PDA, homogeneous conductive networks were formed, firmly coated onto an elastic PDMS skeleton. The sensor exhibited ultra-wide detection, high sensitivity, excellent cycling stability for pressure detection, and fast photothermal conversion (2.346 °C/s under the near-infrared light with an optical power density of 0.85 W cm⁻²) for photothermal therapy. This sensor could detect human motion and perform photothermal therapy based on time-sharing multiplexed technology. Electromyogram (EMG) recordings and analyses verified its healthcare potential, especially the monitoring and timely alleviation of muscle fatigue.