Highly stretchable metallized spandex fibers for large-strain sensing and flexible electromagnetic interference shielding

While high stretchability and electrical reliability are essential for wearable electronics, achieving consistent performance under large deformations remains a significant challenge. Here, we report highly stretchable and conductive silver-plated spandex fibers for integrated applications in strain sensing and electromagnetic interference (EMI) shielding. To optimize sensing performance, we systematically compare three bundle configurations: parallel, twisted, and coiled. Among these, the twisted bundle exhibits the optimal balance between sensitivity (i.e., gauge factor) and mechanical stability. To further enhance reliability, we introduce a pre-strain plating strategy at 30% strain, which induces a wrinkled surface morphology of the silver coating layer upon strain release. During subsequent stretching, these wrinkles unfold, effectively minimizing random crack generation in the silver layer and significantly reducing hysteresis (maximum hysteresis ~4.5%). Furthermore, we extend this metallization to spandex fabrics for flexible EMI shielding, demonstrating excellent attenuation performance of 45 dB with a single fabric layer. These findings suggest that our silver-plated spandex platform offers a practical solution for next-generation wearable motion monitoring and electronic protection.