Understanding and harnessing biomimetic molecular machines for NEMS actuation materials

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.