Physicists Use DNA-Based Nanowires to Conduct Electricity

The world’s smallest transistor is now smaller than the AIDS virus. In the past 60 years, the industry has reduced the size of the central elements of computer chips to 14 nm. However, traditional methods are reaching their physical limits.

Researchers worldwide are on the lookout for alternative methods, and self-organization of complex components from atoms and molecules could be one method.

A key advancement has now been made by scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Paderborn University. They have successfully conducted a current via gold-plated nanowires that assembled themselves independently from individual DNA strands. The scientific journal Langmuir has published the results of the study.

The nanowires look like wormy lines against a black background at first glance. However, they are the nanometer-sized structures connecting two electrical contacts that can be seen up close using an electron microscope. This sight pleases Dr. Artur Erbe from the Institute of Ion Beam Physics and Materials Research. “Our measurements have shown that an electrical current is conducted through these tiny wires."

The physicist states that this is not self-evident. After all, the components used are made of modified DNA. The researchers produced the nanowires by combining one long single strand of genetic material and shorter DNA segments with the base pairs to create one stable double strand. The structures use this method to independently form themselves into desired structures.

With the help of this approach, which resembles the Japanese paper folding technique origami and is therefore referred to as DNA-origami, we can create tiny patterns. Extremely small circuits made of molecules and atoms are also conceivable here.

Dr. Artur Erbe, HZDR

This strategy, which is known as the "bottom-up” method aims to overturn the traditional production of electronic components. “The industry has thus far been using what is known as the ‘top-down’ method. Large portions are cut away from the base material until the desired structure is achieved. Soon this will no longer be possible due to continual miniaturization.”

Instead, the new method is nature-oriented - molecules use self-assembling processes to develop complex structures.

Golden Bridges Between Electrodes

The elements that will develop would be significantly smaller than the current smallest computer chip components. However, there is one problem. “Genetic matter doesn’t conduct a current particularly well,” points out Erbe. Therefore, he and his team used chemical bonds to place gold-plated nanoparticle on the DNA.

By using a “top-down” method called electron beam lithiography, they eventually made contact with the single wires, electronically. “This connection between the substantially larger electrodes and the individual DNA structures have come up against technical difficulties until now. By combining the two methods, we can resolve this issue. We could thus very precisely determine the charge transport through individual wires for the first time,” adds Erbe.

The test results have demonstrated that though the current is conducted through the gold-plated wires, they rely on the ambient temperature.

The charge transport is simultaneously reduced as the temperature decreases. At normal room temperature, the wires function well, even if the electrons must partially jump from one gold particle to the next because they haven't completely melded together. The distance, however, is so small that it currently doesn’t even show up using the most advanced microscopes.

Dr. Artur Erbe, HZDR

The team intends to incorporate conductive polymers between the gold particles to enhance the conduction. Erbe also believes that the metallization process can be improved further.

However, the physicist is pleased with the results. “We could demonstrate that the gold-plated DNA wires conduct energy. We are actually still in the basic research phase, which is why we are using gold rather than a more cost-efficient metal. We have, nevertheless, made an important stride, which could make electronic devices based on DNA possible in the future.”