Design And Wettting And Optical Trapping Properties Of Cicada Wing-inspired Nanostructured Surfaces Prepared By Microinjection Compression Molding

In recent years,using bionic principles to design and fabricate new materials and structures is a rapidly developing research area.Cicada wing is an important biological prototype in many bionic applications with excellent performance for the unique features such as antibacterial,optical trapping and self-cleaning on its surface.High-efficiency,low-cost,and mass-produced preparation technology is the key to the promotion and application of functional biomimetic surfaces.Microinjection compression molding(?-ICM)combining the efficiency of microinjection molding and the accuracy of nanoimprint lithography is widely used in high-efficient,high-precise,low-cost and large-scale production.Therefore,?-ICM is an ideal approach to fabricate biomimetic surfaces with precision and fine structures.In this dissertation,the biologic behavior,performance and relevant mechanism on the cicada wing are investigated by combining theoretical and experimental methods.The surfaces with cicada wing-inspired nanostructures are molded using?-ICM for the first time.The effect of processing parameters of?-ICM on the aspect-ratio(AR)of surface nanostructure for polymer materials is investigated.Then large-sized replicas with high AR and cicada wing-inspired nanostructure on surfaces are prepared,and the wetting states,optical properties as well as photoelectric conversion and self-cleaning applications are analyzed.The cicada wing surface exihibits a gradient wetting state along its veins.That is,the hydrophilic Wenzel state is transformed to the superhydrophobic Cassie-Baxter state,which is attributed to different radius,height,and gap of the nanopillars on its surface.The gradient wetting state is a key to help the cicada wing maintaining a clean and light weight state.Average reflectance of the cicada wing surface at the wavelength range of 400?1000 nm is about 2%.The nanopillars on the wing surface turn the sudden change of refractive index at the interface into a gradient change,which reduces the Fresnel reflection due to the refractive index change.A nickel template with tapered nanopores is fabricated by combining electroless plating and subsequent electroplating with the natural cicada wing as an original template.A PS replica is molded using?-ICM with the nickel replica as a template.The nanopillars on the PS replica are consistent with those on the natural wing and possess a typical mean diameter of about 156nm and a mean pitch of about 180 nm.In the wavelength scope of 400?1000 nm,the average reflectances of the PS counterpart and PS replica are about 9%and 4%,respectively.A 4?L droplet dropped on the PS replica exhibits a water contact angle(CA)of 143°±2°,which is greater than the CA of 83°±2°on the PS counterpart surface.The PS replica fabricated by?-ICM not only inherits the nanopillars on the natural wing surface,but also its hydrophobic and antireflective properties.A response surface experiment is designed to investigate the effect of three processing parameters of?-ICM,including melt temperature(T_m),mold temperature(T_M),and mold compression force(F_C),on the AR of nanopillars on the PS and polypropylene(PP)replicas.The results show that the T_M is the most significant processing parameter that influences the AR of the nanopillars.T_m and F_C have a similar effect on the AR of the nanopillars on PP replica surfaces,and the effect of the F_C on the AR of the nanopillars on PS surface is more significant than the T_m.Furthermore,there is an interactive effect between the other two when one of the three processing parameters is kept at the center level.The interactive term with the participation of the T_m has the most significant effect on the AR of the nanopillars on the replicas.Applying?-ICM technology,a fast and flexible method is proposed for the successive and mass replication of PS replicas with cicada wing-inspired nanopillared surfaces.The fluoroalkyl silane modificated anodic aluminum oxide(AAO)template facilitates the melt filling and demolding during the?-ICM process,and the AAO template can be reused 50 times without significant physical damage.The bio-inspired PS s urfaces have a CA of 155°±2°and rolling angle(RA)of below 30°.The PS surfaces have an efficient self-cleaning and anti-icing effects and can maintain a stable Cassie-Baxter wetting state under an external dynamic pressure up to 1445 Pa.In the wavelength of 500?1000 nm,the average reflectances of the cicada wing-inspired PS replica surface is about 5%lower than the PS counterpart.After covering PS replica on the surface of the solar cell,its short circuit current density and photoelectric conversion efficiency are increased by 5.2%and 7.1%,respectively.A flexible insert is assembled using easily available porous plate and flexible polymer film.Then,applying?-ICM technology,a fast and efficient method is proposed for successive,mass and one-step replication of polymer microlens arrays(MLAs).The focal length,numerical aperture and f-numberof microlens can be controlled by changing the F_C.That is,the height of the MLAs molded using the only one flexible insert is adjustable to a certain range.All the MLAs molded under the different F_C exhibit a favorable geometrical-morphology uniformity and optical properties.AAO template with compound eye lens array is prepared by using imprinting and anodic oxidation.Applying?-ICM,compound eye lens array is prepared,and the compound eye structure contains both the microlens and bio-inspired nanostructure.Surface of the compound eye lens array exhibits a hydrophobic wetting state and the average reflectance is about 4.5%at the wavelength scope of 400?1000 nm.