Flexible Superamphiphobic Film with a 3D Conductive Network for Wearable Strain Sensors in Humid Conditions

A three-dimensional (3D) conductive network with high sensitivity and a wide response range is applicable for wearable strain sensors. However, structural deformation of the 3D network under mechanical stimuli gives rise to mass pores, which are easily soaked by rain, sweat, oil, and so on, thus affecting the sensitivity of the sensors. Herein, a stretchable film with outstanding superhydrophobicity is proposed for reliable strain sensors based on a 3D conductive network. First, superconductive carbon black (SCB) nanoparticles are assembled on electrospun fibers of thermoplastic polyurethane (TPU) to form a TPU/SCB conductive film. Then, a dispersion of carbon nanotubes (CNTs) and fluorinated silica (F-SiO2) is sprayed on the TPU/SCB film to form a conductive TPU/SCB@CNTs/F-SiO2 composite film. After immersion of the composite film in a mixed solution of poly(dimethylsiloxane) (PDMS) and perfluorodecyltrichlorosilane (PFDTS) and drying, a flexible conductive superamphiphobic film was obtained. When the film was used as a strain sensor, it showed superior sensitivity (12.05-60.42), a wide strain range (0-100%), a fast response time (75-100 ms), and good stability in stretching-relaxing cycles. Benefiting from the favorable superamphiphobicity, the obtained strain sensor could be effectively utilized to display stable electrical signals underwater and monitor human motions under dry/sweat exposure, showing significant potential in practical wearable sensors for stretchable, breathable, and reliable human behavior monitoring.