A new fabrication method integrates programmable DNA origami shapes and conventional lithography approaches to develop metallic nanoantennas and chiral shapes for varied applications.
DNA assisted lithography: bowtie-shaped DNA origami is transformed into a metallic nanostructure. (Video credit: M. Kostiainen and V. Linko)
Research teams from University of Jyväskylä and Aalto University (Finland) together with researchers from California Institute of Technology (Caltech, USA) and Aarhus University (iNANO Center, Denmark) have reported a new extremely parallel method to fabricate precise metallic nanostructures with engineered plasmonic properties by means of different self-assembled DNA origami shapes. The so-called DALI (DNA-assisted lithography) technique has been published in the recent issue of Science Advances.
We can build virtually any nanoscale shape using a DNA origami technique, and now we have shown how to use these accurate shapes as “stencils” to create millions of fully metallic nanostructures with 10 nm feature sizes in one go.
Adjunct Professor Veikko Linko, Aalto University
The trick in the DALI technique is that when the DNA structures are placed on a chip coated with silicon, silicon oxide can be selectively grown just on the bare areas of the substrate.
By controlling this process, we can create origami-shaped openings on the grown silicon oxide layer, and this layer can be used as a mask for the following lithography steps. Finally, we evaporate metal through these openings and create metallic structures having the same shape and size as the original DNA origami on a transparent substrate, such as sapphire.
Boxuan Shen, Nanoscience Center of University of Jyväskylä
The miniature metallic features cover the entire transparent substrate and thus these surfaces have fascinating optical properties. The small dimensions of the structures, measuring in the range of ten nanometers, allow additional tweaking of these properties at the visible wavelength range.
“Actually, we have demonstrated here a structure that we believe is the world’s smallest entirely metallic bowtie-shaped antenna. This extremely small size extends the operating range of optical features from infrared to visible”, states Adjunct Professor Jussi Toppari from Molecular Electronics and Plasmonics group at University of Jyväskylä.
These antennas can find use in several plasmonic and optical applications, such as biosensing, surface enhanced Raman spectroscopy, or fluorescence enhancement. Furthermore, the researchers showed that the surfaces can be employed as polarizers by fabricating chiral structures using DALI.
The DALI method is highly parallel, and it could further enable cheap wafer-scale production of surfaces as it does not rely on costly patterning methods. It is also equipped for the future studies to provide bioinspired surfaces and metamaterials if the customized origami structures can be arranged on the substrate before metallization.
Professor Mauri Kostiainen, Biohybrid Materials Group - Aalto University