Electrostatically Driven Nanoballoon Actuator

We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation

Molecular Self-Assembly in a Poorly Screened Environment: F₄TCNQ on Graphene/BN

We report a scanning tunneling microscopy and noncontact atomic force microscopy study of close-packed 2D islands of tetrafluoro­tetracyanoquinodimethane (F₄TCNQ) molecules at the surface of a graphene layer supported by boron nitride. While F₄TCNQ molecules are known to form cohesive 3D solids, the intermolecular interactions that are attractive for F₄TCNQ in 3D are repulsive in 2D. Our experimental observation of cohesive molecular behavior for F₄TCNQ on graphene is thus unexpected. This self-assembly behavior can be explained by a novel solid formation mechanism that occurs when charged molecules are placed in a poorly screened environment. As negatively charged molecules coalesce, the local work function increases, causing electrons to flow into the coalescing molecular island and increase its cohesive binding energy