Fabrication And Microfluidic Control Of Intelligent Response Slippery Surface Based On Femtosecond Laser

Femtosecond lasers has unique advantages in the field of micro/nano processing due to its small heat-affected area and high processing accuracy.In recent decades,with the development of micro/nano manufacturing technology and its application in various fields,surface science has received enormous attention from the researchers.Surface wettability,as a branch discipline of surface science,describes the properties and characteristics of behavior between liquids and solid surfaces.This thesis mainly studies the manipulation of micro-fluid(droplets/bubbles)behavior on the slippery bionic functional surface prepared on femtosecond laser.The on-demand control of droplet sliding and pinning behavior and unidirectional transport of bubbles are realized,and the potential applications in microfluidic manipulation is demonstrated.The main content of the thesis includes the following two parts:(1)We fabricate a kind of dual-responsive smart slippery lubricant-infused porous surfaces(DRSS)by femtosecond laser cross-scanning on flexible polydimethylsiloxane(PDMS)sheets.By cooperation of alternately freezing/thawing and stretching the DRSS,the controllable behavior between sliding and pinning for various micro-sized droplets are achieved.Diverse parameters are quantified to investigate the critical sliding volume of the droplet,including lubricant infusion amount,laser-scanning power,microgroove spacing,tilt Angle and humidity.The underlying mechanism is discussed and is attributed to the friction resistance regulation at the DRSS-droplet interface induced by both stretching force and temperature fields,which change the surface roughness and the targeted droplet physical state on DRSS.Based on the selective volume screening function between droplet sliding and pinning,we investigate its potential applications in microfluidic manipulation and other fields.(2)Femtosecond laser is used to prepare the tracks with micro-nano rough structures on the Polytetrafluoroethylene(PTFE)film,and then it is lubricated to obtain a slippery Janus film with isotropic wettability.The unidirectional transport of bubbles can be conveniently switched via flip of the Janus film.Different from the reported Janus film with wettability gradient,the slippery Janus film controls the penetration of bubbles by the surface energy difference on both sides of the slippery track.The influence of femtosecond laser scanning speed on the surface morphology of Janus film,as well as the influence of track spacing and tilt angle on the unidirectional transport of bubbles are investigated.The unidirectional transport phenomenon of bubbles on Janus film was demonstrated.