Creating Clever Spin Coating Models

Nanosphere lithography, despite its name, has nothing to do with printing. It is actually a very cost effective method of producing regular strictures of nanoparticles quite quickly. It works by creating a mould called a mask made from a single layer of polystyrene nanospheres. In regular printing lithography a surface is treated so that it repels ink and everywhere that doesn’t gets the image formed on it. This polystyrene acts in a similar way as to form a lattice through which the required chemical can pass. The materiel being deposited lands on the substrate in designated positions that force the nanostructure to form in particular places. The arrays produced like this often go on to spend their lives as either sensor components or further latices to grow more advanced nanostructures on. This means that consistency is very important.

In order to make sure that the deposited material forms a uniform and controlled thickness the ideal method would be to use a more operator available spin-coating process. Spin coating is where the material wanting to be layered is placed in the middle of a disk that is then spun at high speeds to that the chemical is distributed to the edges. The faster the spin, the higher the evaporation, the thinner the layer and so long as only small amounts of material are used the formation is quite uniform. The spin process is quite a bit more complicated than this and the effects of viscosity, volatility and concentration need to also be taken into account explaining the amount of research being put into it. Using modelling and predictive experimentation understanding and prediction of spin coating when applied to the polystyrene nanospheres has been achieved. The real brilliance of this model is that it was able to cut down on the complicated parameters until only two remained: the solid/liquid volume ratio and the spin speed. Simplifying such a tricky process makes development in this technique easier and so the whole subject of nanosphere lithography is advanced.

Paper links: Model for large-area monolayer coverage of polystyrene nanospheres by spin coating


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