Programmed self-assembly of microscale components using biomolecular recognition through the avidin–biotin interaction

Abstract

Following continuing trends in nanofabrication, the near future may see the requirement to integrate and assemble devices and integrated circuits that are below the scale that conventional robotic pick-and-place systems can successfully accommodate. Presented here is a protein–ligand based approach to self-assembling micronscale components onto specific patterned locations on a substrate. Other than the benefits in scale, this integration method may be advantageous for its parallel nature, 3D capabilities, and the ability to integrate devices made from incompatible processing technologies into a single platform (heterogeneous integration). Five micrometer square silicon microtiles were fabricated as model devices for microscale integrated circuits. They were fabricated from a silicon-on-insulator substrate and released into solution by bath ultrasonication after the buried oxide layer underneath them was underetched. A silicon target substrate was also patterned with gold pads for the microtiles to assemble onto. Self-assembled monolayers were employed to functionalize both the microtiles and the gold pads with biotin and avidin, respectively. Due to the very strong protein–ligand binding between avidin and biotin, the functionalized microtiles in solution were able to attach onto the target gold pads with a high selectivity. In this demonstration, for 5 μm square microtiles assembling onto square gold pads of the same size, 2.0% of the gold pads were covered by the microtiles and a selectivity (microtiles assembling onto the gold pads as opposed to the silicon substrate) of 7.3:1 was achieved.