The Composite Janus Membrane Was Fabricated By Femtosecond Laser To Realize Fog Collection

Inspired by natural biological diversity,recent years,more and more researchers began to study the special functions and structures of creatures.Inspired by the unique structures of natural creatures such as cactus spines,spider silk,and desert beetles that could collect water from fog of misty environment,researchers had developed a number of biomimetic materials in a variety of ways.Furthermore,femtosecond lasers bionic micro/nano machining had always been a heat topic in the field of materials research.Based on the advantages of the extremely short pulse,peak value and the effect of processing without thermal influence,femtosecond lasers was widely substituted for the complex physical and chemical method.In this paper,advanced ultra-fast femtosecond laser micro-nano technology was used to fabricated composite mesh combined with aluminum and PDMS,the experimental parameters,such as the distribution of surface temperature field when laser interacted with materials,pulse energy,scanning velocity and the distance of the adjacent laser beam,had been regulated to fabricated specific micro/nanostructures with special functions.The details were as followings:First,we expounded the related concepts of bionics and analyzed the present situations of the water resources,secondly,introducing the different functional structures used for fog collection,such as cactus spine,spider silks,and desert beetles,once more,we analyzed the research results of fog collection about researchers in recent years.At last,we proposed the research significance of this paper.Second,this paper mainly analyzes the relevant process parameters of femtosecond laser micro-nano machining platform and the relevant components of the system.We described the femtosecond laser amplifier stage in the principle of optical path system,and the components in the actual road light modulation of micro-nano processing with regulating role of some of the pulse energy,we analyzes the femtosecond laser micro-nano processing platform of the three modules namely femtosecond laser system,precision machining system and computer control system module.In addition,we also use the finite element multi-physical field simulation to simulate the influence of single pulse and multiple pulse on the microporous morphology of aluminum foil surface and the influence of pulse peak value and the thickness of materials on the microporous morphology of composite membrane were studied.Finally,a kind of composite Janus mesh with regular tapered micropores array realized by one-step femtosecond laser drilling was proposed for high-efficiency fog-harvesting.The composite mesh was composed of hydrophilic aluminum foil on the lower surface and hydrophobic Polydimethylsiloxane(PDMS)on the upper surface,and thus showed opposite wetting on both sides of the mesh.The droplets could directionally transport through the tapered micropores due to the wetting driving force and the Laplace pressure.The influence of the structure parameters on the wetting of the composite membrane was studied;compared the phenomenon of water collection and the efficiency of fog collection between single wetting membrane and composite membrane.It was indicated that the composite mesh showed unique self-driving phenomenon and an enhancement of 178%in the aspect of fog-harvesting efficiency.In addition,this mesh did not require chemical materials modification,which presented environmentally friendly sample in practical application.This work may offer an alternative way for the application of femtosecond laser fabrication in fog collection.