Fabrication of superhydrophobic nanofiber fabric with hierarchical nanofiber structure

Polyvinylidene fluoride (PVDF) nanofiber fabric, polyvinylidene fluoride/polyethylene glycol (PVDF/PEG) nanofiber fabric and polyvinylidene fluoride/polyethylene glycol/silicon dioxide (PVDF/PEG/SiO2) nanofiber fabrics are fabricated through a combination of electrospinning and weaving technology, inspired by the "lotus effect". Nanofiber surfaces with a hierarchical nanofiber structure in the PVDF/PEG and PVDF/PEG/SiO2 nanofiber fabrics are formed by hydrolyzing PEG and doping with SiO2 nanoparticles, which is similar to the surface structure of a lotus leaf. The structures of these three fabrics are characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) and the mechanical properties and wettability are analyzed. The results show that the fiber structure of the PVDF/PEG composite nanofiber doped with SiO2 nanoparticles after water scrubbing is composed of many balls, which are formed by the embedding of the SiO2 nanoparticles in the polymer. Moreover, the "ball" is not only similar to the "hill" of a lotus leaf surface, but also similar to the "small thorn" on the "hill" because of the embossment of SiO2 nanoparticles on the "ball" surface. The ultimate tensile strength and failure strain of the PVDF/PEG/SiO2 nanofiber fabric are 92.12 MPa and 18.98%, respectively. The PVDF/PEG/SiO2 nanofiber fabric exhibits superhydrophobicity with a water contact angle of 173.2 degrees.