Adv. Mater. 25, 3593–3598 (2013)

Credit: © 2013 WILEY

The density of optical data storage is usually constrained by the diffraction limit of light. Now, Mohammad Mottaghi and Chris Dwyer from Duke University in the USA have demonstrated a technique that can exponentially increase the density of bits stored, enabling a 1,000-fold increase in density beyond that permitted by the diffraction limit. Their technique, called polychromatic address multiplexing (PAM), exploits nanoscale fluorescence and Förster resonance energy transfer (FRET). A PAM disk consists of several physical storage layers, each containing storage cells with photo-erasable PAM elements (PEPEs). Each PEPE is composed of an ultraviolet-disruptable FRET pair placed on a grid-like DNA nanostructure in which donor (E) and acceptor (R) molecules act as excitation and read ports, respectively. Each cell stores several logical words — a collection of bits associated with a single address. A word address is a unique combination of incident excitation wavelengths used to activate a subset of the PEPEs in the cell. The binary value of an addressed word is translated by exploiting acceptor saturation in ER-PEPEs to induce a fluorescence enhancement. This enhancement is exclusively caused by the addressed structures; other structures remain inactive. The team says this approach can be applied to other data multiplexing applications.