Copper Nanowire-Sealed Titanium Dioxide/Poly(dimethylsiloxane) Electrode with an In-Plane Wavy Structure for a Stretchable Capacitive Strain Sensor

Although copper nanowire (Cu NW) has been considered to be one of the most promising conductive materials with low price and high conductivity, there have been a modest number of studies on Cu NW for stretchable applications. One of the fundamental problems that has limited the application of Cu NW is degradation of the conductivity due to fast oxidation. In addition, a complicated fabrication process, poor structure design, and low durability have also prevented the practical application of Cu NW. We propose an all-solution processing method to fabricate a Cu NW-based stretchable electrode with improved reliability. When Cu NWs were sealed with titanium dioxide and poly(dimethylsiloxane), the electrode exhibited long-term electrical stability. The stretchable electrode showed a low resistance change (ΔR/R₀), 0.2 under an applied tensile stress (ϵ) of up to 50%, and ΔR/R₀increased only 10% after 1000 stretching cycles at ϵ of 30%. The sealed Cu NWs were applied to an interdigitated capacitive strain sensor (ICSS). The fabricated ICSS showed a linear response of the gauge factor (GF) with ϵ = -1.47 from theoretical calculations and -1.23 from the experimental results. Furthermore, the device displayed a stable sensing performance during a repeated stretching test at ϵ of 30% for 400 cycles.