Data storage requirements are increasing dramatically and therefore much attention is being given to next-generation data storage media. However, in optical data storage devices the storage density is limited by the wavelength of light. This limitation can be avoided by an alternative data addressing mechanism using electric fields between nanoelectrodes with smaller dimensions than the wavelength of commercially available lasers. It has been shown that DNA of a range of lengths can be aligned in an electric field [1, 2]. In this study we demonstrate the use of an ac electric field to address DNA as a data storage technique.
λ-DNA, immobilised on an array of electrodes utilising its self-assembling properties, serves as a scaffold for fluorescent molecules. The DNA is immobilised onto gold electrodes in a multi-step procedure ensuring a controlled surface coverage of the molecules onto specific electrodes. To minimise background fluorescence and to enable reversible stretching, the substrate surface is silanised prior to DNA immobilisation. Using a strong, spatially confined ac electric field (1MV/m, 400kHz) the DNA molecules on each electrode are individually and reversibly stretched into a focused Argon laser beam. The fluorophores (YOYO1, Molecular Probes) are rapidly photobleached when the power density of the beam is increased, allowing for data storage when associating a photobleached data point with a binary 1 and an intact data point with a binary 0 (Figure 1). The resulting pattern of high/low fluorescence intensities is read by measuring the fluorescence intensity, using the same dielectrophoretic addressing mechanism, but in conjunction with a much reduced power beam. Although this concept of data storage has been demonstrated only on the micrometre scale, it is a promising candidate for miniaturisation, potentially to the molecular scale.
Figure 1. A pattern of selectively stretched λ-DNA on an array of 4 gold electrodes. Photobleaching the stretched DNA in this configuration will result in a 1, 0, 1, 0 signal when reading back by sequentially stretching the DNA on each electrode into a reduced power beam. The DNA is being stretched in a 1 MV/m, 400 kHz ac field. The electrodes are 10 μm in width and 15 μm apart.
M. Wasizu, and O. Kurosawa, IEEE T. Ind. Appl, 1990, 26, 1165.
M. Wasizu, O. Kurosawa, I. Arai, S. Suzuki, and N. Shimamoto, IEEE T. Ind. Appl, 1995, 31, 447.