An illustration of the memory device consisting of a thin DNA biopolymer film sandwiched between electrodes. The memory-switching effect is activated upon light irradiation. (Credit: Yu-Chueh Hung et al.)

Researchers from National Tsing Hua University in Taiwan and the Karlsruhe Institute of Technology in Germany have created a DNA-based memory device that is “write-once-read-many-times” (WORM), and that uses ultraviolet (UV) light to encode information.

The device consists of a thin film of salmon DNA that has been embedded with silver nanoparticles and then sandwiched between two electrodes. Shining UV light on the system enables a light-triggered synthesis process that causes the silver atoms to cluster into nano-sized particles, and readies the system for data encoding. In some cases, using DNA may be less expensive to process into storage devices than using traditional, inorganic materials like silicon, the researchers say.

At first, when no voltage or low voltage is applied through the electrodes to the UV-irradiated DNA, only a low current is able to pass through the composite; this corresponds to the “off” state of the device. But the UV irradiation makes the composite unable to hold charge under a high electric field, so when the applied voltage exceeds a certain threshold, an increased amount of charge is able to pass through. This higher state of conductivity corresponds to the “on” state of the device.

Once information is written, the device appears to retain that information indefinitely. The authors hope the technique will be useful in the design of optical storage devices and suggest that it may have plasmonic applications as well.

Ref.: Yu-Chueh Hung, Wei-Ting Hsu, Ting-Yu Lin, and Ljiljana Fruk, Photoinduced write-once read-many-times memory device based on DNA biopolymer nanocomposite, Applied Physics Letters, 2011; [DOI:10.1063/1.3671153]