One Novel Hybrid Flexible Piezoresistive/Piezoelectric Double-Mode Sensor Design for Water Leakage Monitoring

Water leakage is a significant issue in infrastructure, such as submarine tunnels, which can lead to major disasters and property losses. Therefore, it is of great significance to develop a water leakage detection sensor with simple preparation process, low cost, and small limitation of applicable location. In this study, a novel hybrid flexible piezoresistive/piezoelectric double-mode sensor with a sandpaper negative microstructure is proposed. A unique dual-path perception structure is designed that can simultaneously and independently detect two signals of water leakage frequency and water leakage volume. The piezoresistive layer is formed by polydimethylsiloxane (PDMS) coated with multiwalled carbon nanotubes (MWCNTs), which is molded by sandpaper molding. By sensing the deformation caused by the swelling of superabsorbent polymers (SAPs), the water leakage volume can be detected as low as 0.5 mL. The piezoelectric layer is a polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) film prepared by the spin-coating method, and the water leakage frequency (0.5–4 Hz) is detected by direct contact with water droplets. This work also studied the performance of the double-mode sensor under low temperature and seawater leakage conditions and further verified its reliability in different environments. The design of the new hybrid flexible piezoresistive/piezoelectric double-mode sensor provides a new possibility for water leakage monitoring, such as in submarine tunnels.