Torsional carbon nanotube artificial muscles.

Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.

Bond order effects in electromechanical actuation of armchair single-walled carbon nanotubes.

In this paper we first use ab initio simulations to study the strains induced by charging an armchair (5,5) carbon nanotube (CNT) segment. The observed behavior is far from a monotonic expansion that one might have expected from a classical point of view. Subsequently a new method is proposed to predict the nonelectrostatic part of the electromechanical actuation response of the nanotube based on the spatial distribution of its molecular orbitals. Locally bonding and locally antibonding molecular orbitals are defined for the CNT segment structure based on analogy with bonding and antibonding orbitals in diatomic molecules. The nonmonotonic overall actuation is explained based on the above proposition and the general alignment of the expanding and contracting bonds with respect to the axis or circumference of the CNT segment. Using the well-known concept of bond order, the actuation of this complex system of many atoms is predicted with close quantitative agreement with the ab initio simulations.

Supramolecular assembly of carbohydrate-functionalized salphen-metal complexes.

Metallosalphen complexes with peripheral glucose and galactose substituents were synthesized and characterized. Their self-assembled supramolecular structures were then studied with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that all of the complexes displayed aggregation in the solid-state. Zinc-salphen complexes showed a remarkably homogeneous helical nanofibrillar morphology, whereas the other metal complexes only displayed micron-sized clusters.

Electromechanical actuation of single-walled carbon nanotubes: an ab initio study.

The mechanical actuation of a (5, 5) single-walled carbon nanotube as a result of added charge is simulated using first-principles calculations. It is observed that while both positive and negative charging tend to expand the nanotube in the axial direction for most levels of charge, radial actuation is less even and symmetric with respect to charge. The spin distribution of the additional charges is investigated, and it is predicted that in some cases unpaired spin configurations are energetically favourable, significantly affecting actuation strains.