Fractal Gold Nanoframework for Highly Stretchable\nTransparent Strain-Insensitive Conductors

Abstract

Percolation networks\nof one-dimensional (1D) building blocks (e.g.,\nmetallic nanowires or carbon nanotubes) represent the mainstream strategy\nto fabricate stretchable conductors. One of the inherent limitations\nis the control over junction resistance between 1D building blocks\nin natural and strained states of conductors. Herein, we report highly\nstretchable transparent strain-insensitive conductors using fractal\ngold (F–Au) nanoframework based on a one-pot templateless wet\nchemistry synthesis method. The monolayered F–Au nanoframework\n(∼20 nm in thickness) can be obtained from the one-pot synthesis\nwithout any purification steps involved and can be transferred directly\nto arbitrary substrates like polyethylene terephthalate, food-wrap,\npolydimethylsiloxane (PDMS), and ecoflex. The F–Au thin film\nwith no capping agents leads to a highly conductive thin film without\nany post-treatment and can be stretched up to 110% strain without\nsignificantly losing conductivity yet with the optical transparency\nof 70% at 550 nm. Remarkably, the F–Au thin film shows the\nstrain-insensitive behavior up to 20% stretching strain. This originates\nfrom the unique fractal nanomesh-like structure which can absorb external\nmechanical forces, thus maintaining electron pathways throughout the\nnanoframework. In addition, a semitransparent bilayered F–Au\nfilm on 100% prestrained PDMS could achieve to a high stretchability\nof 420% strain with negligible resistance changes under low-level\nstrains.