We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO(2) membranes as electrode materials. A thin TiO(2) film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF(4) aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO(2) film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO(2) membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO(2) membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N(')-bis(2,2(')-bipyridyl-4,4(')-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO(2) film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO(2) membranes. The efficiency of the fibrous TiO(2) photoelectrode with the average membrane thickness of 3.9 µm has a maximum value of 4.14%.

Inspired by biointerfaces, such as the surfaces of lotus leaves and pitcher plants, researchers have developed innovative strategies for controlling surface wettability and transparency. In particular, great success has been achieved in obtaining low adhesion and high transmittance via the introduction of a liquid layer to form liquid-infused surfaces. Furthermore, smart surfaces that can change their surface properties according to external stimuli have recently attracted substantial interest. As some of the best-performing smart surface materials, slippery liquid-infused porous surfaces (SLIPSs), which are super-repellent, demonstrate the successful achievement of switchable adhesion and tunable transparency that can be controlled by a graded mechanical stimulus. However, despite considerable efforts, producing temperature-responsive, super-repellent surfaces at ambient temperature and pressure remains difficult because of the use of nonreactive lubricant oil as a building block in previously investigated repellent surfaces. Therefore, the present study focused on developing multifunctional materials that dynamically adapt to temperature changes. Here, we demonstrate temperature-activated solidifiable/liquid paraffin-infused porous surfaces (TA-SLIPSs) whose transparency and control of water droplet movement at room temperature can be simultaneously controlled. The solidification of the paraffin changes the surface morphology and the size of the light-transmission inhibitor in the lubricant layer; as a result, the control over the droplet movement and the light transmittance at different temperatures is dependent on the solidifiable/liquid paraffin mixing ratio. Further study of such temperature-responsive, multifunctional systems would be valuable for antifouling applications and the development of surfaces with tunable optical transparency for innovative medical applications, intelligent windows, and other devices.

As frost formation and ice accumulation result in serious problems in various industrial systems, some anti-icing system is highly required, and passive anti-icing processes based on ice prevention coatings have attracted much attention. Recently, antifreeze liquid-infused surfaces (LISs) have been developed for the preparation of ice-phobic surfaces owing to their low ice adhesion strength and antifrosting properties. However, it is still challenging to add an optical function such as high transparency to antifreeze LISs despite the potential for the application in window coatings. In addition, the influence on anti-icing properties by the thickness of antifreeze liquid layer and base layer are still unclear. Here, we designed highly transparent coating surfaces that were resistant to ice adhesion and frost formation. We controlled the thickness, surface roughness, and refractive index of the base layer through a spray layer-by-layer (LbL) method and then investigated the effect on the optical properties, ice adhesion strength, and frost formation behavior. The frost-resisting properties of the surfaces were clearly improved with the increase of the lubricant thickness as well as the increase of the number of bilayers; the parallel transmittance of antifreeze LIS composed of ethylene glycol and this base layer was approximately 92.6%, and the ice adhesion strength was below 17 kPa regardless of the number of bilayers. These results indicated that a high lubricant thickness coating can achieve both excellent anti-icing properties and transparency; the antifreeze LIS based on a 100 bilayer base coating had excellent antifrosting properties owing to its thick antifreeze liquid layer and maintained both of high transparency and low ice adhesion. Furthermore, the spray LbL method makes it possible to fabricate the base layer in short time and also in large scale, which is quite useful for the practical application of antifreeze LIS. This work will be of enormous help for the design of transparent anti-icing coatings as well as industrial applications such as solar cells and the windows of transportation vehicles.

We fabricated slippery liquid-immobilized coating (SLIC) films by reacting a slippery liquid (polymethylhydrosiloxane) near the surface of a polyelectrolyte film containing silver ions prepared by the layer-by-layer method. The obtained films maintained their slipperiness after chemical and physical treatments, in contrast to slippery liquid-infused porous surfaces. The high chemical and physical stabilities of the films were attributable to gelation and immobilization of the lubricant owing to an oxidation-reduction reaction with subsequent dehydration condensation of Si-OH on the outer surface of the polyelectrolyte film and the bonding of Si-H with NH groups within the polyelectrolyte film, respectively. Moreover, the SLIC films exhibited a high degree of slipperiness with respect to low-surface-tension liquids. To the best of our knowledge, this technique of lubricant immobilization using silver ions has not been reported previously. The films should be suitable for use in various applications where contamination must be prevented under extreme conditions, such as those requiring high physical durability and organic solvent use.

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