Biomolecular electronics: Protein-based associative processors and volumetric memories

The promise of new architectures and more cost-effective miniaturization ha s prompted interest in molecular and biomolecular electronics. Bioelectroni cs offers valuable near-term potential, because evolution and natural selec tion have optimized many biological molecules to perform tasks that are req uired for device applications. The light-transducing protein bacteriorhodop sin provides not only an efficient photonic material, but also a versatile template for device creation and optimization via both chemical modificatio n and genetic engineering. We examine here the use of this protein as the a ctive component in holographic associative memories as well as branched-pho tocycle three-dimensional optical memories. The associative memory is based on a Fourier transform optical loop and utilizes the real-time holographic properties of the protein thin films. The three-dimensional memory utilize s an unusual branching reaction that creates a long-lived photoproduct. By using a sequential multiphoton process, parallel write, read, and erase pro cesses can be carried out without disturbing data outside of the doubly irr adiated volume elements. The methods and procedures of prototyping these bi oelectronic devices are discussed. We also examine current efforts to optim ize the protein memory medium by using chemical and genetic methods.