Self-alignment of microstructures based on lateral fluidic force generated by local spatial asymmetry inside a microfluidic channel

Three-dimensional (3D) microstructures have various applications in many fields due to their unique physical properties. Manufacturing 3D microstructures with precise micron-scale features is difficult. Although the assembly of two-dimensional (2D) structures is a smart way to construct complex 3D microstructures, the way to assemble those 2D structures precisely is still immature. One key issue is that alignment errors often occur during the assembly process, affecting the architecture accuracy of the assembled 3D structures. In this paper, we propose a method to eliminate the alignment error during the self-assembly process only by lateral fluid force. Theoretical analysis has been conducted to demonstrate how alignment errors in the assembly channel are automatically corrected, during which a force perpendicular to the flow direction is generated by the channel’s local spatial asymmetry to automatically correct those alignment errors. Besides, the movement of microstructures in the channel has been numerically simulated, whose results were consistent with the theoretical analysis, and there was indeed a lateral force that causes the self-aligning of the microstructure in the channel. The effect of the microstructure’s dimensions and the channel’s size for self-alignment procedure has also been analyzed. It shows that the self-alignment of the microstructure can complete when the ratio of the diameter of microstructures to the width of the channel is greater than 85%. Besides, experiments of the self-alignment between adjacent layers of microstructures were successful, which show the presented idea using lateral fluid force is a promising way to build 3D structures with less assembly errors.