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

Abstract

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/R 0 ), 0.2 under an applied tensile stress (ε) of up to 50%, and ΔR/R 0 increased 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.

Recent Advances in Nanowire-Based Wearable Physical Sensors

“…NW-based capacitive strain sensors have emerged as promising devices for strainsensing applications [49,65,[87][88][89][90]. These sensors utilize the unique properties of NWs to achieve highly sensitive and accurate measurements of strain.…”

Liquid Metal and Carbon Nanofiber-Based Strain Sensor for Monitoring Gesture, Voice, and Physiological Signals

“…1 Soft and stretchable strain sensors, as one of the important elements in the family of wearable sensors, 2,3 have undergone development from traditional wire and/or foil strain gauges 4−6 to ultrathin-film-state strain sensors, 7 for the purpose of making them respond simultaneously to the epidermic changes 8,9 and realizing precise detection. 10 In addition, numerous contributions have been made to strain sensors by the use of newly developed materials, such as lowdimensional carbon materials, 11,12 biomass, 13,14 metal nanowires, 15,16 MXene fabric, 17,18 as well as hydrogels 19,20 and composites 21 loaded with nanoconductive fillers, as well as the recently proposed crack-based strain sensors by imitating slit sensilla of arthropods. 22 The optimizations of stretchable electronic materials and their layout to construct elastic and conductive networks are the key points in the studies of soft strain sensors.…”

“…Soft and stretchable strain sensors, as one of the important elements in the family of wearable sensors, , have undergone development from traditional wire and/or foil strain gauges − to ultrathin-film-state strain sensors, for the purpose of making them respond simultaneously to the epidermic changes , and realizing precise detection . In addition, numerous contributions have been made to strain sensors by the use of newly developed materials, such as low-dimensional carbon materials, , biomass, , metal nanowires, , MXene fabric, , as well as hydrogels , and composites loaded with nanoconductive fillers, as well as the recently proposed crack-based strain sensors by imitating slit sensilla of arthropods . The optimizations of stretchable electronic materials and their layout to construct elastic and conductive networks are the key points in the studies of soft strain sensors. , For example, the micro crack-junctions’ disconnection–reconnection of a 20 nm film on a viscoelastic polymer can contribute to the ultrahigh gauge factor (GF = 2000); meanwhile, the zigzag crack structure on flexible and interlaced graphene ribbons was demonstrated to improve sensitivity. , The main idea in crack-based strain sensors is focused on how to make the conductive layer split and coalesce by integrating ductile metals (such as Au, Ag, and Cu) and viscoelastic polymers [such as poly­(urethane acrylate) (PUA) and poly­(ethylene terephthalate) (PET)].…”

Improving the Performance of Transparent Conducting Electrodes Based on Cu Nanowires

“…CuNWs are metallic and can change to Cu 2 O or CuO which are semiconductive [13][14][15][16][17][18]. Some methods have been investigated to overcome these intrinsic problems, either in synthesizing CuNWs using coating materials [19][20][21][22][23][24] or fabricating the TCEs [25][26][27]. Tong et al [28], suggest enhancing the stability of CuNWs through the application of an in situ carbon protective layer coating.…”