This paper describes the design, assembly, fabrication, and evaluation of artificial molecular machines with the goal of implementing their internal nanoscale movements within nanoelectromechanical systems in an efficient manner. These machines, a unique class of switchable molecular compounds in the shape of bistable [2]rotaxanes, exhibit internal relative mechanical motions of their ring and dumbbell components as a result of optical, chemical, or electrical signals. As such, they hold promise as nanoactuation materials. Although micromechanical devices that utilize the force produced by switchable [3]rotaxane molecules have been demonstrated, the current prototypical devices require a mechanism that minimizes the degradation associated with the molecules in order for bistable rotaxanes to become practical actuators. We propose a modified design in which electricity, instead of chemicals, is employed to stimulate the relative movements of the components in bistable [3]rotaxanes. As an initial step toward the assembly of a wholly electrically powered actuator based on molecular motion, closely packed Langmuir-Blodgett films of an amphiphilic, bistable [2]rotaxane have been characterized and an in situ Fourier transform infrared spectroscopic technique has been developed to monitor molecular signatures in device settings. Note to Practitioners-Biological molecular components, such as myosin and actin in skeletal muscle, organize to perform complex mechanical tasks. These components execute nanometer-scale interactions, but produce macroscopic effects. Inspired by this concept, we are developing a new class of mechanical nanodevices that employ a group of artificial molecular machines called bistable rotaxanes. In this paper, a series of experiments has been conducted to study the molecular properties of bistable rotaxanes in thin films and on solid-state nanodevices. Our results have shed light on the optimization of future molecular machine-based systems particularly with respect to their implementation and manufacture.

Novel organic memory devices including nonvolatile and write-once-read-many-times memory devices are reported. These devices were fabricated through a simple solution processing technique. Programmable electrical bistability was observed on a device made from a polymer film containing metal nanoparticles capped with saturated alkanethiol and small conjugated organic compounds sandwiched between two metal electrodes. The pristine device, which was in a low-conductivity state, exhibited an abrupt increase of current when the device was scanned up to a few volts. The high-conductivity state can be returned to the low-conductivity state by applying a certain voltage in the reverse direction. The device has a good stability in both states, and the transition from the low- to the high-conductivity state takes place in nanoseconds, so that the device can be used as a low-cost, high-density, high-speed, and nonvolatile memory. The electronic transition is attributed to the electric-field-induced charge transfer between the metal nanoparticles and small conjugated organic molecule. The electrical behavior of the device is strongly dependent on the materials in the polymer film. When gold nanoparticles capped with aromatic thiol were used, the device exhibited a transition from low- to high-conductivity state at the first voltage scan, and the device in the high-conductivity state cannot be returned to the low-conductivity state. This device can be used as a write-once-read-many-times memory device.