Molecular Motors, Actuators, and Mechanical Devices

that drive components to perform useful work. The conversion of electrical and chemical energy into mechanical motion is facilitated by the use of gears, bearings, drive shafts, springs, and so forth, to direct the motion of components and minimize energy losses. Thus, research efforts dedicated to produce these sorts of components are considered to be both a direct pathway in our Roadmap and an enabler of other pathways that can take advantage of these molecular mechanical devices and the fabrication techniques developed to produce them. This section summarizes the state-of-the-art in the construction of these devices and describes their relevance to the Roadmap. Table 3 at the end of this section provides a summary of representative molecular motors, actuators, and mechanical devices. Electric Nanomotors and Nanoactuators. In 2003, the Zettl Group at Lawrence Berkeley Laboratories and UC Berkeley fabricated the smallest-known non-biological nanomotor [3]. The device employed a multi-walled carbon nanotube (MWNT), which served as both a bearing for the rotor and as an electrical conductor, and had the following characteristics: • Doped silicon substrate covered with 1μm SiO2. • Rotor, anchor pads, and electrodes—constructed lithographically; 90 nm gold layer with 10 nm Cr adhesion layer • Rotor length 100 – 300 nm • Bearing—MWNT's, 10-40 nm diameter, 2 μm length between anchor pads • Torsional spring constant of the outer nanotube, 10