Smart fabrics and wearable electronics can be developed using highly conductive and stretchy fibers. Most of these fiber conductors are, however, strain sensitive with limited conductance on stretching. As a result, a new strategy can be introduced by rearranging the geometry of the conductive path for stable conductance. In a new report now published on Science Advances, Lijing Zheng and colleagues in China and Germany, described a coaxial wet-spinning process to continuously develop intrinsically stretchable and highly conductive, yet conductance-stable liquid metal (LM) sheath-core microfibers. The team stretched the microfibres up to 1170 percent and fully activated the conductive path to obtain a very high conductivity of 4.35 x 104 S/m and a resistance change of only 4 percent at 200 percent strain. The microfiber could be woven easily into everyday glove fabrics and as excellent joule heaters, electro-thermochromic displays and self-powered wearable sensors.
Stretchable fiber conductors
Stretchable fiber conductors can be easily developed into fabrics with high air permeability and can be well integrated as wearable sensors with increasing interest. Stretchable conductive fibers have highly sensitive conductance changes and promote stable conductance. Recent developments in high-performance electronics have a high demand for stretchable fiber electrodes or interconnects to steadily transport electrical signals between active electronic components without notable conductance loss. To overcome existing limits, Zheng et al. embedded deformable conductive fillers with strain-enhanced conductivity into an elastic matrix to produce ultralong, intrinsically stretchable fiber conductors with stable and high conductance. The research team proposed a coaxial wet-spacing method to prepare super-elastic liquid metal sheath-core microfibers with high and ultra-stable conductance. They then explored the promising applications of the liquid metal sheath-core microfibers in smart fabrics and self-powered sensing processes, relative to joule heating, electrothermochromism and triboelectric properties.
The experiments—preparing the liquid-metal (LM) sheath-core microfibers.
Zheng et al. used coaxial wet-spinning to prepare liquid metal sheath-core microfibres and improved the fiber quality by smoothly solidifying the spinning solution. They used three spinning solutions in the inner channel and distilled water in the outer channel as the coagulating bath. The team also introduced a covalent network in the sheath post-ultraviolet polymerization to improve the toughness and elastic recovery of the LM sheath-core fiber. Based on the strategy, Zheng et al. could continuously wet-spin the LM sheath-core microfibers into an ideally unlimited length. After fully drying the microfiber, they imaged the product using scanning electron microscopy (SEM) to observe a uniform and regular surface. The team next sowed good electrical conductivity of the fibers using a light-emitting diode (LED).