Research On The Directional Self-elasticity Performance Of Condensed Droplets On The Surface Of Biomimetic Nano-ratchet-like Structures

Bionic nano ratchet structure is a ratchet like structure composed of asymmetric nano arrays.On the surface,it has an anisotropic inclined nano wire array.It makes the surface have ability to transport objects in a directional way.Anisotropic surfaces comprised of organized asymmetric nanostructures have provided the basis for diverse functions due to their direction-dependent properties,such as directional liquid self-transportation by condensed microdroplet self-jumping(CMDSJ).However,it is still a challenge to facile fabricate the organized asymmetric nanostructures to realize the directional CMDSJ.On the other hand,mechanical properties of the nanosurface is a key factor influencing the CMDSJ,which is always ignored.Here,inspired by the inclined tapered setae on the leg of water striders,inclined nanohair arrays which form a ratchet structure is facilely fabricated at low cost and large area by nanoimprinting followed by directional template removing.Microdroplets with diameter larger than 10?m show directional CMDSJ on this surface whose mechanical properties(hardness and modulus)are strengthened by depositing silica nanoparticles.This is because the moving droplet suffers less lateral force which prevents the movement of the droplet as moving along the inclined direction of the nanohair than that moving along the opposite direction.The process of fusion and ejection of two droplets with diameter of 10 ?m is simulated.The simulation results are corresponding to the experiment well.This work shows a facile way to obtain anisotropic structure with directional CMDSJ property and has a deep insight into how mechanical properties of the nanostructure influence the CMDSJ.The main research details are concluded as follows:1.Preparation of inclined nano wire arrays and characterization of their hydrophobic properties:The inclined nanowire array structure with bionic ratchet was prepared on the surface of ETFE by using the nanoimprinting followed by directional template removing.The samples were evaporated with silica particles of 0 nm,15 nm and 30 nm in thickness,and then they were modified with fluorosilicone to obtain a surface of ETFE with bionic ratchet like inclined nanowire array structure.The results of EDS,XPS and FT-IR showed that the surface of 15 nm and 30 nm samples were covered with silica particles.Surface with superhydrophobic properties and directional CMDSJ was obtained.The influence of mechanical properties(hardness and modulus)of vacuum evaporated silica particles on the directional self driving performance of condensed droplets was systematically studied.With the increase of SiO2 thickness,the tip size of nanowires increases,the contact Angle decreases,the rolling Angle increases,and the adhesion force at the solid-liquid interface increases.2.Study on the performance of condensed microdroplet self-jumping(CMDSJ):The condensed microdroplet self-jumping(CMDSJ)properties of silica particles with different thickness of 0 nm,15 nm and 30 nm were studied.The surface of 30 nm SiO2 inclined nanowires has excellent self-jumping performance of directional condensation droplets.Therefore,the mechanical properties of these samples were tested,and it was found that the mechanical properties were one of the important parameters affecting the microdroplet self-jumping(CMDSJ).The condensation behavior of two 10 ?m condensed droplets on the surface of 30 nm inclined silica nanowires was numerically simulated,and the simulated structure was consistent with the experimental results.