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Poly(chloro-p-xylylene) (PPXC) film has a water contact angle (WCA) of only about 84°. It is necessary to improve its hydrophobicity to prevent liquid water droplets from corroding or electrically shorting metallic circuits of semiconductor devices, sensors, microelectronics, and so on. Herein, we reported a facile approach to improve its surface hydrophobicity by varying surface pattern structures under different temperature and relative humidity (RH) conditions on a thermal curable polydimethylsiloxane (PDMS) and hydrophobic silica (SiO2) nanoparticle coating. Three distinct large-scale surface patterns were obtained mainly depending on the contents of SiO2 nanoparticles. The regularity of patterns was mainly controlled by the temperature and RH conditions. By changing the pattern structures, the surface wettability of PPXC film could be improved and its WCA was increased from 84° to 168°, displaying a superhydrophobic state. Meanwhile, it could be observed that water droplets on PPXC film with superhydrophobicity were transited from a “Wenzel” state to a “Cassie” state. The PPXC film with different surface patterns of 200 μm × 200 μm and the improved surface hydrophobicity showed wide application potentials in self-cleaning, electronic engineering, micro-contact printing, cell biology, and tissue engineering. [ABSTRACT FROM AUTHOR]

Building a superhydrophobic coating on polymer films is an important way to obtain water-proof surfaces. However, due to the poor mechanical strength and weak adhesion between coating and substrate, the superhydrophobicity of the coating is easily lost under mechanical loads. In this study, a facile approach was proposed to build a mechanically stable superhydrophobic poly(chloro- p -xylylene) (PPXC) film by pre-coating a polydimethylsiloxane adhesive layer (PDMS AL) on the original PPXC film and coating a superhydrophobic PDMS and silica (PDMS/SiO 2 ) layer on the PDMS AL layer. As demonstrated by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) measurements, the thermal cross-linking reaction between the PDMS/SiO 2 coating and the PDMS AL layer could dramatically promote the interaction between the PDMS/SiO 2 coating and the PPXC film. By tuning pre-curing time and the content of PDMS AL, the mechanical stability of the PDMS/SiO 2 coating on PPXC film could be adjusted. Under the optimal conditions of pre-curing time and the content of PDMS AL, the PPXC film showed robust superhydrophobicity and self-cleaning ability against various mechanical damages, such as 3M tape peeling and cyclic abrasion. The superhydrophobic coating on PPXC film with PDMS AL showed a higher peeling resistance than that on PPXC film without PDMS AL. Moreover, the superhydrophobic coating on PPXC film with PDMS AL maintained its original superhydrophobicity even after 4000 cycles of abrasion. [ABSTRACT FROM AUTHOR]

Special wettability of biological surfaces usually depends on the unique micro-structures and surface chemistry natures. However, current preparation methods often involve complex processing steps or expensive moulds and have the limited ability to simulate these ordered and elaborate micro-structures. Herein, we report a facile and mould-free approach to fabricate special wetting surfaces by patterning an ordered porous structure with various geometric parameters via one-step 3D printing of Polydimethylsiloxane (PDMS) ink. By adjusting pore structure at sub-millimeter scale, the printed PDMS porous films can present versatile special surface wettabilities such as superhydrophobicity and anisotropic wettability. With the guide of computer program, water contact angles (WCAs) along parallel and perpendicular directionsand anisotropy wetting degree of the printed film can be tailored by controllingprinting speed and filament spacing. Through optimizing the geometrical parameters, a superhydrophobic PDMS filmwith a WCA of about 155° is obtained, which mainly depends on the sub-millimeter scale structure. The superhydrophobicity of the printed porous PDMS film also exhibits excellent durability against thermal aging. Our work demonstrates that the printed superhydrophobic porous film can be used for some attracting applications such as air-breathable water-proofing, water-repellent floating carrier, and no-loss liquid transfer. [ABSTRACT FROM AUTHOR]