A permeable and stretchable liquid metal fiber enables ultrahigh-linearity and wide-range strain sensors

Wearable strain sensors hold great promise for applications in personalized health monitoring, human-machine interaction, and intelligent healthcare, whereas developing strain sensors with both high linearity and wide strain range remain a significant challenge. Here, we present a simple strategy to address this issue by taking advantage of carbon nanotubes as a rigid conductive skeleton and a fluidic liquid metal as a dynamically conductive phase, realizing a permeable and stretchable fiber strain sensor with an ultrahigh linearity of 0.9999 over a wide strain range of up to 359%. Polydopamine self-assembles on the fiber surface to create an adhesion layer that immobilizes carbon nanotubes and liquid metal, thereby enhancing the continuity and stability of the composite conductive network, with a detection limit down to 0.1% and stability over 3000 cycles. The strain sensor also shows the strong photothermal response (The linearity between light intensity and saturation temperature reaches as high as 0.997) under different light intensities. Moreover, the high breathability and moisture permeability is verified through forearm skin irritation tests and water vapor permeability measurements. Exceptional performance achieves comprehensive detection of human movement and application in the human-machine interaction systems. This research reconciles the trade-off between linearity and sensing range, enhancing the development of high-performance strain sensors for intelligent robotics and wearable electronics.