Orientation-specific fluidic self-assembly process based on a capillary effect

The investigation develops a novel design of a two-dimensional modified alignment mark of a tear-drop/elliptical hole with a tip angle of 60°. TDE-1 and TDE-2 pattern shapes are adopted to increase the recovery angle and reduce the energy barrier to uni-directional micropart alignment. The results of the experimental and surface energy models are compared, both qualitatively and quantitatively, to examine the feasibility of the new design patterns. Experimental results reveal that the micropart of the TDE patterns can be accurately aligned by rotation through 90° and a large capillary force. The acrylate adhesive force of the TDE-2 patterned micropart was estimated to be 41.2±10 νN. Fluidic self-assembly (FSA) was performed in an aqueous environment, using a low-temperature solder or acrylate adhesive in part-substrate lubricant and template-assisted assembly. The standard deviation of the aligned angular orientation was 0.9° and the lateral accuracy was 15 νm; the re-aligned assembly yield was 100%. Micropart self-alignment with a unique in-plane orientation is achieved by exploiting shape recognition with the adhesive capillary effect. © 2009 IOP Publishing Ltd.