Fabrication And Properties Of PDMS-Based Transparent Superhydrophobic Surfaces

High transparency is one of the basic requirements for optical devices,such as smart windows,solar panels and camera lens to function well.However,frequent exposure of these devices to different outdoor environments,inevitably stains their outermost surfaces,which may diminish their performance.Thus,it is necessary to clean them regularly.As is known to all,superhydrophobicity of lotus leaf surfaces endows them with self-cleaning benefit,also regarded as "in the silt but not imbrued".Applying this principle to optical devices,not only can keep their surfaces clean,maintain its specific functionality,and also reduce laborious manual cleaning and dosage of detergent,favouring both environmental protection and energy saving.Therefore,fabrication and properties of transparent superhydrophobic surfaces become the hot topic of research in recent years.Polydimethylsiloxane(PDMS)is a kind of hydrophobic organic silicon material with good chemical stability,excellent weather-resistance and high transparency.It is widely used in preparation of transparent superhydrophobic surfaces.In this research,transparent silica nanotubes(SNT)coatings with certain micro roughness on glass substrates were fabricated by using PDMS as the silica source and octadecylamine functionalized multi-walled carbon nanotubes(MWCNTs-ODA)as the sacrificial template.Then the as-obtained coatings were turned superhydrophobic through chemical vapor deposition(CVD)of cured PDMS.The influence of experimental factors on the transparency and wetting performance of coatings was revealed in detail.The results showed that transparency of SNT decreased with the increasing of the concentration of PDMS in spraying solution and that increased initially and then unchanged with the increasing of calcination temperature and extension of calcination time in the process of removing template.The increasing of amount and extension of deposition time of cured PDMS in the process of CVD caused the water contact angle(CA)to increase and the water slide angle(SA)to decrease,and the transparency of coatings also reduced gradually.The optimum coating has an average transmittance higher than 83% in the visible-light range of(400~780 nm),a CA of 165° and a SA lower than 3°.Importantly,the coating maintained excellent superhydrophobicity and transparency after 480? calcination,impact with 500 mL water,4 h ultrasonic treatment as well as 48 h strong acid or strong alkali dipping.When applied as protective cover,the transparent superhydrophobic coatings had little side effect on the power generation efficiency of solar cells and had outstanding self-cleaning properties,showing a great application prospect.