We have investigated tantala nanodot and nanocones arrays through the fundamental research. Artificial Moth-eye structures by using hollow-to-solid nanocones were successfully fabricated for high-performance AR coatings.
Quasi-closely packed arrays of cone-like nanostructures are fabricated by the anodization of Al/Ta bilayers coated on substrates. We proposed the mechanism of formation of the hollow NCA due to the stress of gaseous O2. The porosity of the hollow nanostructures is calculatedly controlled by varying the deposited thickness of Ta film. The transmissions of the glass substrates coated with hollow NCA of 65.5%
porosity reached greater than 97.8% over the whole visible range. Besides, the reflectivity was suppressed greatly in a broadband omnidirection and reached as low as 10% at an incident angle of 70°. In other cases of porosity, NCA coatings were also found as an efficient ARS on sapphire and AlN substrates. Good mechanical stability makes NCA suitable for protective coatings for optical transparency. The availability of the hollow nanostructures has allowed the design of artificial optical properties as new building blocks (e. g. diffractive layer, diffusers, or reflectors) in future photonic devices.
Moreover, we also have fabricated hollow TiO2 nanocones under PAA featuring TiO2 NTs within directly on FTO glass and used them as new working electrodes in DSSCs. By depositing a thin layer (15-nm-thick) of Ti on a FTO substrate prior to anodization, we obtained self-organized hollow TiO2 nanocones, with improved contact between the FTO substrate and the overlaying Al, thereby solving the problems of delamination of an undesirable barrier. This more-stable PAA/FTO structure was highly suitable for use in subsequent sol–gel processing of Ti(OiPr)4.
The novel structure combines two types of TiO2 materials—0-D nanocones and 1-D NTs—to benefits from a large contact area, direct electron transport path, and slow recombination of electrons. The unique morphology provided a photocurrent of 5.15 mA/cm2, an open circuit voltage of 0.64 V, and an IPCE peak of 26% from an 800-nm-thick NT array. The relatively short NT array results in a considerably lower photoabsorption than, for example, the current DSSC ―gold standard‖ featuring a tens-of-micrometers-thick layer of TiO2 NTs. We suspect that increasing the length of the NT array on the electrode might allow us to further improve the efficiencies of such DSSCs. The facile synthesis of this novel architecture may allow the design of new nanostructures for use as new building blocks in future electro-optical devices.
We successfully presented an approach to fabricate angled taper nanohair arrays as an excellent directional, reusable and water cleanable gecko-mimicking dry adhesive in large area. From Dahlquist‘s criterion, an ideal taper nanohair of PUA that consist a length of 1.3 μm and a diameter of 380 nm was designed. By using taper PAA mold via decoupling two-step HA process reported firstly by us, taper nanohairs with slanted angle were fabricated. The angled taper nanohair did facilitate the stability and self-cleaning properties compared with pillar nanohairs while still maintain a great directional adhesion. Moreover, remarkably directional force exhibited by angled taper nanohair arrays is showing here with strong shear attachment ( ~8 N/cm2) in the gripping direction and easy releasing( ~1.4 N/cm2) in the reverse direction (pulled against the angled direction of hairs). The smart adhesive presented here would enable the climbing robots, cleaning transport system such as LCD factory and non-residue sticker for future generation. A further study should be done on longer length or stiffer material to improve the adhesion capability against rough surfaces outside the laboratory.
Plane PDMS treated by the simple acid texture exhibited regular periodic
wrinkles whose periodicities were in a micro-scale. Two superhydrophobic surfaces with self-cleaning and high water adhesion were obtained. The resulting superhydrophobicity caused only by the topography changing instead of chemical modification. Owing to the silicon back bone in PDMS, the fabricated surface displayed mechanical stable superhydrophobicity under acidic and basic corrosive environments and a long duration. The complicated rose petal topography manufactured by duplicating the close-packed polystyrene beads and acid corrosion process. The petal-like surface of superhydrophobicity and high adhesive force for water we fabricated had three structural levels including micro-convexes, nano-wrinkles and nanostructures. The resulting micro-convex, provided high-water adhesive ability due to van der Waals interaction, while nano-wrinkles and nanostructures provided superhydrophobicity caused by the lotus effect. The unique property including superhydrophobicity and high-water adhesion was suitable for applying in liquid transportation. Unlike hairy type and tube type superhydrphobic surfaces, excessively strong adhesive force is disadvantageous to water-releasing.
Futhermore, the fabricated material can use in future nonresidual imprint technique.
We were firstly combined the ―lotus effect‖ and ―petal effect‖ to fabricate the nonresidual stamp. The stamp remained cleanly even though it was used for thousand times. From the point of applications, the technique we proposed is applicable in biotechnology, chemical engineering industry, and microfluidic devices.
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