Static Electricity can Control Nanoballoon

Electrostatically Driven Nanoballoon Actuator, Nano Letters (2016). http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b02394

Molecular sized machines could in the future be used to control important mechanisms in the body. In a recent study, researchers at University of California, Berkeley and Umeå University show how a nanoballoon comprising a single carbon molecule can be controlled electrostatically to switch between an inflated and a collapsed state. Inflatable balloon actuators are commonly used for macroscopic applications to lift buildings, as impact protection in cars or to widen narrowed or obstructed arteries or veins. At the micro scale they are used as micro pumps and in nature jumping spiders create microformat fluid-filled cushions to power their legs in explosive jumps.

Interestingly, at the nanoscale, balloon actuators are virtually unknown. However, a few years ago researchers at the Penn State University theoretically proposed a charge controlled nanoballoon actuator based on the collapsing and reinflation of a carbon nanotube.

Now, this has been realized experimentally by Hamid Reza Barzegar et al who show how a carbon nanotube can be controlled to transform from a collapsed to an inflated state and vice versa by applying a small voltage. The defect-free nature of carbon nanotubes imply that such an actuator would be able to work without wear or fatigue. This is also shown by the researchers who run the actuator over several cycles with no signs of loss in performance.

“The work is conceptually interesting and gives insight into the complexity of how to control motion at the nanoscale by external stimuli” says Dr Hamid Reza Barzegar. “It also gives insight into fundamental physics such as how the capacitance effect and in general the electrostatic forces can be used to control the dynamics of molecular structures.”

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.

“In a longer perspective one can also envision how our findings could be used for pneumatic control on molecular level or for designing molecular containers that can open or close by controlling the surface charges of the molecules, by for example tuning the pH of the solution in which the molecules are dispersed. This could for example be of use for medical applications such as for delivering medicine to internal organs or tumors” says A/Prof Thomas Wågberg, Umeå University.

The discovery of molecular machines was awarded this year’s Nobel prize in Chemistry. Jean-Pierre Sauvage, Fraser Stoddart and Bernard L Feringa got the prize for having developed molecules with controllable movements, which can perform a task when energy is added.
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