The Research On Fabrication Of Droplet/Bubble Unidirectional Transport Composite Membrane By Femtosecond Laser

After millions of years of evolution and selection,species in nature have evolved and selected micro/nano structural interfaces with special wettability in order to adapt to environmental changes.Therefore,the formation of specific wettability interfaces by preparing micro/nanostructures has become an urgent problem for researchers.This paper combined with femtosecond laser micro/nano processing technology and bionic design principle,and designed the micro/nano structure region with specific wettability according to relevant engineering application requirements.Firstly,the main components of the femtosecond laser micro/nano processing system were analyzed.On this basis,the mapping relationships between the pulse energy and the pulse number of femtosecond laser on the ablation micropore size of the aluminum foil surface were studied.Then,we explored the design and preparation of droplet unidirectional transport model based on superhydrophilic/superhydrophobic micropore array aluminum foil and bubble unidirectional transport model based on hydrophilic/superhydrophobic(aerophobic/superaerophilic)micropore array aluminum foil.And the droplet/bubble unidirectional transport mechanism was systematically studied.The details"were as follows:(I)The main structures of femtosecond laser micro/nano processing system were revealed.Based on multi-scale theory of the interaction between femtosecond laser and materials,the mapping relationships between the pulse energy and the pulse number of femtosecond laser on the ablation pore size of the aluminum foil surface were studied.And the controllable preparation of different micropore size arrays on the surface of aluminum foil was realized.(2)In combination with the current development and the scientific problems of droplet unidirectional penetration in fluid handling,we proposed a superhydrophilic/superhydrophobic Janus membrane for droplet unidirectional transport.The wettability state of water by micropore array aluminum foil with different structure and chemical composition was studied.Compared with the single penetration or interception of double-faced superhydrophilic or superhydrophobic membranes,the Janus membrane showed a distinctive droplet unidirectional transport ability.The droplets introduced on the upper superhydrophobic surface could spontaneously move to lower superhydrophilic surface,but they were prevented in the inverse direction.And the mechanism of interception or penetration or unidirectional transport of three different wettability membranes was analyzed.(3)In combination with the current development and the scientific problems of bubble unidirectional penetration in bubble manipulation,we proposed a hydrophilic/superhydrophobic(aerophobic/superaerophilic)Janus membrane for bubble unidirectional transport.The Janus aluminum foil membrane was fabricated by laser drilling,low surface energy modification and subsequent fluorination removal.The effects of micro/nano structure and chemical element content on the wetting state of water and bubble on the surface of aluminum foil were analyzed.Compared with the single interception or penetration of double-faced hydrophilic or superhydrophobic membranes,the Janus membrane showed a distinctive bubble unidirectional transport ability.In experiment,the bubbles introduced on the lower hydrophilic surface could spontaneously move to upper superhydrophobic surface,but they were blocked in the inverse direction.The dynamic process of unidirectional transport was in-situ monitored,and the physical mechanism was systemically investigated.In addition,the concepts of air-participating chemical/physical processes were demonstrated such as discoloration of purple litmus solution by CO2 injection,which proved the Janus membrane practicability.The aluminium foil with complex wettability based on femtosecond laser processing has unique functions and effects in the field of droplet/bubble unidirectional transport.It provides a potential research scheme and design idea for industrial applications such as liquid distillation,micro-chemical reaction operation,advanced separation,biomedical materials and so on.