Fabrication Of Superdrophobic Polymer Surfaces By Using Pdms And Metal Templates

With the continuous developments of micro/nano-technologies, people have learned much about state-of-the-art microstructures from natural materials, and are trying to find out approaches to mimic these natural materials. The demands of tailored surfaces, such as superhydrophobic surface, also motivate people to explore the physical and chemical mechanisms of materials properties at micro- or nano-scale. This superhydrophobicity has attracted tremendous interest in both fundamental researches and practical applications.Two hypothesis, Wenzel model and Cassie model, were put forward to explain the influence of surface roughness on the wettability (so-called "lotus effect"). Recently, some scientists have already demonstrated the feasibility of fabricating artificial superhydrophobic surfaces via lithography-based etching, surface depositing, template-based extrusion, etc. Nevertheless, most of these reported approaches are costly with rigorous experiment conditions, such as clean-room facilities, or are restricted in some certain applications. In this paper, poly(dimethylsiloxane) (PDMS) stamps were firstly prepared by replica molding against fresh lotus leaves. Then low-density polyethylene (LDPE) was melted and pressed onto the featured surface of the PDMS stamp in a vacuum oven. After being cooled to room temperature and being peeled off from the stamps, the LDPE films with superhydrophobic surface were created. FE-SEM imaging showed that the superhydrophobic surface had micro-papillas much higher than these on the lotus leaf, demonstrating the papillas had been stretched longer from the holes on the stamp during separating process.Inspired by above unexpected find, metal templates with micro- and nano- roughness were created by chemical etching metal surfaces such as stainless steel, brass and aluminum alloy. Different etching process for different metal surface was studied and the best processes for each metal were optimized by thermal pressing polymers on these templates. FESEM imaging confirmed that the polymer surfaces micromolded by using metal templates also possess stretched papillas and superhydrophobicity.The interaction between the polymer and the template holes should be responsible for such stretching. This means superhydrophobic polymer films would be produced in large scale easily only if a stainless rolling mold with randomly but proportionally spaced microholes was created.