Nanoscience and nanotechnology: The bottom-up construction of molecular devices and machines

The bottom-up approach to miniaturization, which starts from molecules to build up nanostructures, enables the extension of the macroscopic concepts of a device and a machine to molecular level. Molecular-level devices and machines operate via electronic and/or nuclear rearrangements and, like macroscopic devices and machines, need energy to operate and signals to communicate with the operator. Examples of molecular-level photonic wires, plug/socket systems, light-harvesting antennas, artificial muscles, molecular lifts, and light-powered linear and rotary motors are illustrated. The extension of the concepts of a device and a machine to the molecular level is of interest not only for basic research, but also for the growth of nanoscience and the development of nanotechnology.