Thin films dried from colloidal suspensions have wide applications, such as paint and varnish. To meet the requirements of emerging applications such as energy and electronic device, a multifunctional coating is necessary. Instead of multi-step deposition methods, a cost-effective single step method is preferred to save time and reduce cost. When mixed together, particles with different size or charge will segregate vertically upon drying. In this work, the effects of Peclet number, humidity and volume fraction on the thin film surface profile were examined with atomic force microscopy (AFM). Image analysis was performed to analyze the results from AFM. The results showed that there was a dependence of volume fraction and Peclet number ratio on the surface structure of the thin films. On the surface of thin films, the volume fraction of big particles decreased with increasing Peclet number ratios and increasing volume fraction of big particles. The effect of humidity on the surface profile of thin film was not obvious. The results were compared to literatures with systems of different particles and sizes. We concluded that the surface structures of thin films could be controlled by controlling the Peclet number ratios and volume fractions of each content. The results are promising in creating a cost-effective single-step method for paints, vanishes and coatings in different fields.

Surface profile exploration of thin film auto-stratification with atomic force microscopy

251st National Meeting (2016)

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