Preparation And Property Of Self-healing Superhydrophobic Surfaces

Superhydrophobic surfaces have attracted enormous attention because of their potential applications in self-cleaning,anti-icing,oil-water separation,anticorrosion,and so forth.However,superhydrophobic surfaces are vulnerable to mechanical and chemical damage which lead to the degradation of the surface chemical composition and the collapse of the delicate multi-scale structures,and finally lead to lose the superhydrophobicity,shortening their service lifespan,and cause unnecessary waste.In this paper,three kinds of superhydrophobic surfaces are prepared by molecular design and nanotechnology,achieving the super-hydrophobic repairability,micronano structure repairability and ultra-fast self-repairability.And the self-healing mechanism is explained respectively.This research provides a new insight into the design of robust superhydrophobic surfaces.In order to achieve the restoration of superhydrophobicity,we synthesized Cu/TiO₂ composite material via a facile one-step method,using the adhesion property of dopamine,directly anchoring TiO₂ nanoparticles and n-dodecanethoil onto the surface of copper foam.This superhydrophobic Cu/TiO₂ foam will lose its superhydrophobicity and changed into superhydrophilic under ultraviolet irradiation.Interestingly,this Cu/TiO₂ foam can restore the superhydrophobicity under heat treatment,this restoration can attribute to the migration of n-dodecanethoil onto the surface,lowering the surface energy and exposing alkyl chain to air.Meanwhile,the water contact angle?WCA?could maintain at 149.2° even after seven times cycle of irradiation and heat treatment.As a result,a smart robot “strider” could float at both water/air and water/oil interfaces,using copper foams with UV switchable wettability as supporting legs,which improved the adaptability of aquatic equipment to complex aqueous environment.In order to restore the surface micro-nano structure,a superhydrophobic aerogel was prepared under the coordination of catechol group and Fe³⁺ ions',followed by surface modification of sliver particles and octadecylamine?ODA?.The superhydrophobic aerogel was able to restore its superhydrophobicity under heat treatment even after losing the hydrophobic capacity under plasma ions etching.The aerogel could keep a high WCA above 150 after 11 cycles of etching/heating.In addition,once the aerogel is scratched or cutoff by a knife,the micro/nano-structures and configuration can achieve self-recover via wetting and heating processes,thus,resulting in the recovery of superhydrophobicity and mechanical properties.The mechanism for the recovery of configuration and mechanical property lies in dynamic catechol-Fe³⁺ coordination,which re-crosslinks the broken Alg-DA chains together.The hydrophobicity was repaired by the rearrangement of ODA molecules,which exposed the hydrophobic alkyl chain to air.On the other hand,the micro-nano structure was repaired via ODA melting and recrystallization.In order to achieve ultra-fast restoration of the superhydrophobicity,the gallic acidgrafted polydimethylsiloxane?PDMS-GA?was synthesized.And followed by the filling up with conductive carbon black and TiO₂ nanoparticles into a PDMS-GA network cross-linked by pyrogallol group and Fe³⁺ coordination to achieve superhydrophobic capability.The superhydrophobic conductor could recover its wettability quickly via electric heating after plasma etching.The recovery of superhydrophobicity is due to the Joule effect that the electric heating can make the fluorosilane migrating to the outer surface after electric heating for one minute.The superhydrophobic conductor kept a high WCA above 152° even after 10 cycles of etching/heating.In fact,the superhydrophobic conductor was also able to restore its macroscopic configuration,microstructure,mechanical properties and wettability after severe mechanical damage only by electric heating for one minute.It still kept a WCA above 153.6° and a mechanical properties maintained 83.1% of the original value after the 6th restoration.The ultrafast restoration is mainly attributed to dynamic nature of pyrogallol-Fe³⁺ coordination.These coordination can be weakened by high temperature,dissociating more PDMS-GA molecular chains which will participate in the regeneration of PDMS-GA network.Thereafter,comes out the reconstruction of configuration from macroscopic to nanometer levels.In pratical application,the superhydrophobic conductor can delay the freezing time of water droplets and reduce the adhesion force of ice on the surface of conductor.Thus,the ice layer on the surface of superhydrophobic conductor can be removed quickly by means of electrification.