Prediction of Coating Thickness in the Convective Assembly Process

Convective assembly is a coating method to fabricate thin films with ordered particle structures that can be used extensively for biochemical sensors, data storage devices, optical devices, and other applications. The fluid flow into or through the close-packed region causes the convective assembly, and it is important to understand the formation mechanism of the close-packed region. In this paper, the length of the close-packed region was predicted, and the dimensionless coating thickness as well as the dimensionless length of the close-packed region was found to be the functions of only three dimensionless variables: two capillary numbers and the initial volume fraction. From the modeling results, coating process regime maps that predict the dimensionless coating thickness in terms of the dimensionless variables were created. In addition, the length of the close-packed region was measured under various coating conditions to validate the model prediction. The experiments firmly supported the model predictions.