Operation of devices based on shape transitions in bistable carbon nanotubes
Oleg Shklyaev (The Penn State Universisty)
Instability in Solids and Structures
Tue 10:45 - 12:15
Barus-Holley 190
Oleg Shklyaev, Eric Mockensturm, Vincent H. Crespi The Pennsylvania State University, University Park, PA, 16802-6300, USA The bistability of large-diameter single-wall carbon nanotubes (i.e. inflated and collapsed cross-sections) can be used to design new types of nano-devices such as engines, generators, and heat pumps. We demonstrate that a carbon nanotube can be used as a working body which converts energy into one-dimensional motion by changing the cross-sectional shape from the collapsed to inflated. The equilibrium shape of a carbon nanotube is responsive to different external stimuli such as temperature, applied voltage, and the pressure of a gas inside the tube. Below the critical point where the energies of the inflated and collapsed configurations are equal, the tube assumes the collapsed cross-sectional shape; above this, it is inflated. Tuning the temperature or applied voltage with respect to critical values, we can convert thermal or electrostatic energy into translational motion along the nanotube axis. In the first case, the tube is progressively opened by the entropic effects; in the second-- by the electrostatic repulsion between the tube walls. With this type of control, the shape changing tube can operate as a constant-force spring. We also consider the interaction of a nanotube-engine with an ambient gas as an explicit example of mechanical loading by which the tube can be coupled to the surroundings. When transforming between the inflated and collapsed states, the tube performs work compressing the gas trapped inside a tube. The system can be driven around a thermodynamic cycle by changes in temperature: above (below) the critical temperature the gas expands (contracts) and the tube converts to the inflated (collapsed) state. Controlling the temperature, we create working cycles akin to a Carnot cycle with one arm below a critical phase transition temperature.