Ultimate in microelectronics: Biomolecules

Biological microstructures perform a variety of chemical and electrical functions: switches, proton pumps, power supplies, receptors, effectors, and transducers. In most biological systems, each function is carried out by a separate molecule or as part of a complex of molecules. In a few cases, the same molecule can perform more than one function. Since the larger of these molecules is only 5 nm in diameter, this is the ultimate in miniaturization. Although these processes are not executed rapidly by comparison with solid-state electronics, they are highly efficient. The underlying principles are parallel processes and feedback control, and the mechanisms involve electron tunneling, diffusion within or adjacent to the matrix, charge separation across a highly resistive low-capacity medium, energy stored in chemical bonds, and near-thermodynamic equilibrium pools for electron transport. Thus, a detailed understanding of the structure function relationship using a host of structural and spectroscopic techniques is paramount to design of molecular-based electronic architecture.