Biological molecules like DNA can self-assemble into a variety of complex 2-D and 3-D architectures with very low energy consumption and without the need for expensive patterning tools. In addition, self-assembled DNA templates can also be designed to controllably place functional nanomaterials with molecular precision. These characteristics make DNA an attractive template for fabricating electronic circuits from biological molecules. However, electrically conductive structures are required for electronic applications. In this study, we demonstrate a metallization process that uses gold nanorod seeds followed by anisotropic electroless plating to provide improved morphology and greater control of the final metallized width of conducting metal lines. In addition, we demonstrate the controlled placement of gold nanorods on a DNA breadboard to make rectangular, square and T-shaped metallic structures that are then completed by anisotropic plating.

Nanowire formation begins with a seeding step where gold nanorods are attached to a DNA template to create a seed layer. Electroless gold deposition is then used to fill the gaps between seeds in order to create continuous, conductive nanowires. Importantly, growth during electroless deposition occurs preferentially in the length direction at a rate that is approximately four times the growth rate in the width direction, which enables fabrication of narrow, continuous wires. The electrical properties of nanowires with widths ranging from 13 nm to 29 nm were characterized, and resistivity values as low as 8.9 X 10^-7Ω-m were measured.

For site-specific placement of nanorods to a DNA template, we modified the surface of the gold nanorods with single-stranded DNA. The rods were then attached to DNA templates via complementary base-pairing between the DNA on the nanorods and the attachment strands engineered into the DNA “breadboard” template. Gaps between the nanorods were filled controllably via anisotropic plating to make continuous metallic structures of different shapes. The combination of molecularly directed deposition and anisotropic metallization presented here represents important progress towards the creation of nanoelectronic devices from self-assembled biological templates. Continuing efforts seek to interface these thin DNA metallized structures with active elements to enable device fabrication through self-assembly.