Fluidic self-assembly of microstructures and its application to the integration of GaAs on Si

A new technique for the self-assembly of microstructures is demonstrated in this paper. Freed microstructures suspended in a fluid are assembled onto a host substrate by fluidic transport. The microstructures are fabricated with specific binding features. They are freed from their original substrate by sacrificial etching and transferred into an inert carrier fluid. Before the microstructures are freed, they can also be bonded to an intermediate substrate where their original-substrate is removed. This provides access to the other side of the microstructures for processing before they are freed into the carrier fluid. The fluid is then dispensed onto a host substrate with specific features to control the positioning and the orientation of the microstructures. In this way an abundance of microstructures can be made in advance and assembled onto the substrates as desired. This is especially advantageous for the integration of microstructures and substrates made of incompatible material systems, e.g. GaAs on Si. Microstructures can be fabricated densely packed on the substrate prior to freeing, and the fluid containing them can be recycled to minimize waste. Also, different types of devices can be simultaneously placed at different positions on the host substrates by using selective features that differentiate among devices features.