Voltage Reconfigurable Bio-inspired Devices

Moore’s law of transistor scaling predicts that due to shrinking transistor dimensions and other improvements, the number density of transistors in an integrated circuit would double every two years, resulting in a higher processing speed and performance. However, it is very challenging to continue to reduce the physical dimensions of the transistors. Miniaturization of electronics is very desirable as it will enable faster computational speed and better performance and advance the field of quantum devices, biomedical sensors, and photonics. The future of miniaturized electronics may utilize novel single molecular semiconductors. Molecular electronics may present several unique advantages due to the broad structural variability and small size of molecules, enabling high number density. The intrinsic electrical properties of the single molecules can be studied by attaching them to the electrodes separated by nanometer-scale gaps. Nanogaps facilitate the research to explore charge transport mechanisms and other quantum effects at the nanoscale level. Electron beam lithography (EBL) is a highly precise and reliable technique to construct arrayed nanogaps, and methods have been developed to achieve sub-10 nm channel widths. However, many published approaches are limited in throughput and universality due to multiple lithography steps or specialized techniques. This work describes the fabrication of nanogap arrays with nanogap spacing from 5-40 nm utilizing a simple, single EBL step, continuous dose, and direct feature write method. This method involves optimizing the focusing using sputtered copper to reduce charging and latex nanoparticles to facilitate coarse focus. In addition, cold lithography was utilized to preserve the nanoscale features patterned in the resist. Overall, this protocol enables the straightforward production of electrode nanogaps to facilitate the study of nanoscale materials and effects. A bioinspired reconfigurable molecular electronic material, alloxazine-modified DNA was investigated as a redox-active switch of hydrogen bonding. DNA is promising for nanoscale applications due to its ability to self-assemble into arbitrary nanoscale shapes. An electrical switch of DNA structure through modification of hydrogen bonds would bring rationally-controlled functionality to these constructs. In this project, alloxazine DNA base surrogates were synthesized and incorporated into DNA duplexes as a surrogate base functional as a redox-active switch of hydrogen bonding. Thiolated duplexes were self-assembled onto multiplexed gold electrodes and probed electrochemically. Cyclic voltammetry and square wave voltammetry revealed a redox peak near −0.32 V vs. Ag/AgCl reference, corresponding to the reduction of the alloxazine moiety. Alternating between alloxazine oxidizing and reducing conditions modulated the SWV peak in a manner consistent with the formation and loss of hydrogen bonding, respectively, which disrupts the base pair stacking and charge transport efficiency of the DNA. These results support the assertion that alloxazine is a redox-active switch of hydrogen bonding, useful in controlling DNA and bioinspired assemblies.