Date Published: January 26, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Ruixin Xu, Kaili Zhang, Xiangyang Xu, Minghui He, Fachuang Lu, Bin Su.
Underwater vibration detection is of great importance in personal safety, environmental protection, and military defense. Sealing layers are required in many underwater sensor architectures, leading to limited working‐life and reduced sensitivity. Here, a flexible, superhydrophobic, and conductive tungsten disulfide (WS2) nanosheets‐wrapped sponge (SCWS) is reported for the high‐sensitivity detection of tiny vibration from the water surfaces and from the grounds. When the SCWS is immersed in water, a continuous layer of bubbles forms on its surfaces, providing the sensor with two special abilities. One is sealing‐free feature due to the intrinsic water‐repellent property of SCWS. The other is functioning as a vibration‐sensitive medium to convert mechanical energy into electric signals through susceptible physical deformation of bubbles. Therefore, the SCWS can be used to precisely detect tiny vibration of water waves, and even sense those caused by human footsteps, demonstrating wide applications of this amphibious (water/ground) vibration sensor. Results of this study can initiate the exploration of superhydrophobic materials with elastic and conductive properties for underwater flexible electronic applications.
Fabrication of SCWS Cubes: Commercial melamine–formaldehyde sponges were cut into 1 × 1 × 1 cm3 cubes, then cleaned by alternative acetone and distilled water for two times in an ultrasonic cleaner. The resulted sponge cubes were dried in a vacuum oven at 100°C for 2 h to completely remove potential moisture. Then, these precleaned sponge cubes were dipped into a dispersion of WS2 nanosheets in ethanol (0.1 wt%, purchased from Nanjing Muke Nano company), then underwent vacuum degassing at 100 °C for 2 h or centrifugation assistances at ≈1000 rpm for 1 min , allowing for close contact of WS2 nanosheets with the sponge framework. The amount of WS2 nanosheets was tunable by repeating the “dipping and drying” process. For further hydrophobic modification, WS2‐wrapped sponges were dipped into a dispersion of commercial hydrophobic fumed silica nanoparticles (Aerosil R202, average particle size 14 nm, Evonik Degussa Co.) in ethanol (3 wt%), then underwent vacuum degassing at 100°C for 2 h or centrifugation assistances at ≈1000 rpm for 1 min, yielding SCWS cubes.
The authors declare no conflict of interest.