Electrodes which are both soft and flexible are crucial components for skin-tight wearable electronic devices, e.g., in sportswear. Metal-elastomer nanocomposites are a promising material because they are both stretchable and conductive. However, most prototypes to date suffer from poor cycling stability and insufficient long-term durability.

Takao Someya, University of Tokyo and Center for Emergent Matter Science (CEMS), Wako, both Japan, and colleagues have produced nanofiber-reinforced metal–elastomer composite electrodes for skin-tight textiles. The electrodes are composed of silver flakes, a fluoroelastomer matrix (made from DAI-EL G8001), and polyvinylidene fluoride (PVDF) nanofibers. The PVDF nanofibers were prepared using electrospinning. The composite films were fabricated by stencil printing a silver–fluoroelastomer composite ink on the polyvinylidene fluoride (PVDF) nanofiber sheet. The resulting electrodes were integrated into sensors, which were then built into compression-type sportswear.

The nanofibers increase the material’s toughness and reduce crack propagation in the electrode. The conductivity was found to be four times higher than in a material without the nanofibers. This effect occurs because the fibers act as a filter for the silver flakes, which arrange in a silver-rich layer on top of the material. The electrode is stretchable by up to 800 % and the cyclic degradation was limited to a relative resistance change of 0.56 after 5,000 cycles.

• Highly Durable Nanofiber-Reinforced Elastic Conductors for Skin-Tight Electronic Textiles,
  Hanbit Jin, Md Osman Goni Nayeem, Sunghoon Lee, Naoji Matsuhisa, Daishi Inoue, Tomoyuki Yokota, Daisuke Hashizume, Takao Someya,
  ACS Nano 2019.
  https://doi.org/10.1021/acsnano.9b02297