Based on the ''lotus effect'' principle, smooth microreliefs of polyvinylidene fluoride (PVDF) membrane were prepared via thermally induced phase separation process. Hydroxyl groups were introduced into PVDF membrane by pretreatment with KOH/alcohol solution. Subsequently, these hydroxyl groups grafted with (CH 3 ) 2 SiCl 2 /CH 3 SiCl 3 to form nano-clusters, which were decorated on the microreliefs of PVDF membrane. Scanning Electronic Microscopy (SEM) and Atomic Force Microscope (AFM) analysis showed the micro-and nano-scale structures, similar to lotus leaf, were successfully fabricated on the PVDF membrane surface. The water contact angle and sliding angle on the fabricated lotus-leaf-like PVDF membrane surface were 154 and 4 , respectively. Self-cleaning test indicated that the lotus-leaf-like surface of PVDF membrane has excellent superhydrophobic and self-cleaning properties.
Self-cleaning surfaces have received a great deal of attention recently, both in theoretical studies and commercial applications. Lotus flowers are a symbol of purity in Asian cultures; even though they grow in muddy waters, they remain clean and uncontaminated. The “self-cleaning” surface of their leaves is hydrophobic and rough, showing a micro- and nano-scale morphology. The micro-reliefs of lotus leaves are mimicked by using polyvinylidene fluoride (PVDF) film and the nano-scale peaks on top of the micro-reliefs are implemented by a reaction between CH3SiCl3 and the reactive groups of the PVDF film treated by oxygen plasma. A lotus leaf-like surface of the PVDF film is clearly observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Elemental composition analysis by x-ray photoelectron spectroscopy (XPS) reveals that the material of the nanostructure of the PVDF film is polymethylsiloxane. The superhydrophobic property of the mimicked self-cleaning surface is validated by the water contact and sliding angles on the lotus leaf-like PVDF film, which are 165°and 4°, respectively. In this case, water drops can easily move off the PVDF surface, carrying dust away and leaving a clean surface
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