Liquid metal microspheres enabled photothermally triggered shape memory fibers with strong thermomechanical interfaces for soft robotics and actuator-sensory hybrids

Abstract

Light-driven shape-memory effect offers a promising approach for programmable, untethered actuation in soft robotics and wearable electronics. However, achieving high-efficiency photothermal conversion, robust thermomechanical interface, and integrated multimodal sensing remains challenging, especially on multilayered fibers. Herein, we report a heterogeneous core-sheath fiber-based soft actuator consisting of a wet-spun thermoplastic polyurethane/polycaprolactone (TPU/PCL) core and a conformal sheath coating of photothermally responsive liquid metal microspheres (μLMs). The ultrasonically derived μLMs exhibited adjustable sizes and optical absorption, enabling efficient photothermal welding of waterborne polyurethane (WPU) onto the fiber with robust thermomechanical interfaces. These intriguing characteristics delivered rapid photothermal heating to ~80 °C at 28.9 °C s−1 under 0.85 W cm−2 NIR irradiation and excellent stability over 1000 cycles, sufficient to trigger the phase transition and shape programming of the fiber actuator. Leveraging those properties, fiber-based soft robotics and wearable intelligent textile systems were achieved. Furthermore, by conformally coating Ti3C2Tx MXene on fiber, a multimodal sensing interface capable of detecting NH3 gas and strain can be obtained, with mixed-signal classification achieved through a KNN algorithm. Such a versatile fiber-based devices that seamlessly couples photothermally-triggered actuation and multimodal sensing offer new opportunities for soft, embodied intelligent robotics.