Four exploratory nano-scale devices that take advantage of surface interactions are highlighted in this proposal. The first uses lattice registry to make nano-devices featuring tunable rotary and translational motion. The others use the bistability (tube/ribbon) of nanotubes caused by surface adhesion and atomic-scale registry to develop nano-pumps, vices, switches, and interconnected networks with unique mechanical properties. To determine the feasibility of these devices, new multi-scale modeling techniques must be developed. These models must incorporate the important physics at every level from quantum mechanical to structural. The combined areas of expertise of the PIs covers this full range, allowing them to carefully decide what physics must be included and what can be neglected at each scale. Dr. Crespi's newly developed potential for atomic-scale registry and surface interaction will be integrated into the nonlinear structural theories developed by Dr. Mockensturm using so-called Cosserat continuum mechanics. Theoretical studies of these devices which are difficult and computationally expensive using molecular dynamics become feasible using continuum models. Regardless of the ultimate success of these speculative devices, the new modeling techniques developed will provide a foundation for further device discovery.
As sizes decrease to the atomic scale, surface interactions take on a more important role, to the point where they can induce novel and macroscopically peculiar behaviors. At the ultimate limit of a nanostructure, it is possible for essentially every atom to be at the surface, particularly in carbon-based nanostructures which can have a two dimensional crystalline structure (graphite, not diamond). Long-range surface interactions are, thus, a fundamental mechanism in nano-scale devices that are rarely important in the macroscopic world and typically ignored. At the nano-scale, van der Waals' interactions make devices behave as if they are coated with a thick layer of molasses. These surface interactions allow carbon nanotubes to have two stable states. The most commonly seen state is tubular. However, a so-called nano-ribbon is just another stable (collapsed) state of nanotubes. In this research the investigators will use this bi-stable behavior to develop new modes of nano-device operation. Specifically, the feasibility of nano-pumps, vices, switches, and interconnected networks with unique mechanical properties will be studied.
