Micro- and macro-machines, actuators and "muscles" based on molecular species

devices reminiscent of muscles, based on the association between polypyrrole and a non conducting polymer Soft and Wet Conducting Polymers for Artificial Muscles** By Toribio F. Otero* and Jose M. Sansiñena Adv. Mater. 1998, 10, No. 6,

Conformational changes and subsequent volume changes occurring during electrochemical doping in polypyrrole films.

Movements of a polypyrrole/nonconducting polymer bilayer (c) produced by the local stress gradients and bending originating at the interface between the two layers owing to reversible conformational changes in polypyrrole during oxidation (a) and reduction (b) processes.

Movement of a bilayer device constructed using a 3 mg polypyrrole layer (area 3 cm 2, thickness 6 mm) with a steel weight of 1 g attached to its free end in 1 M LiClO 4 aqueous solution under galvanostatic conditions. The bilayer takes 9 s to move the steel weight through 180° (I = 30 mA). The bilayer without the attached weight takes 7.2 s to perform the same movement under the same applied current.

Nanoscale electromechanical systems—nanotweezers—based on carbon nanotubes have been developed for manipulation of nanostructures. Electrically conducting and mechanically robust carbon nanotubes were attached to independent electrodes. Voltages applied to the electrodes closed and opened the free ends of the nanotubes. The mechanical capabilities of the nanotweezers were demonstrated by grabbing and manipulating submicron clusters and nanowires. pp

(A) deposition of two independent metal electrodes and subsequent attachment of carbon nanotubes to these electrodes. (B) SEM image of the end of a tapered glass structure after the two deposition steps.The two electrodes(top and bottom) are separated by a gap (dark belt in the middle). Scale bar, 1 mm. The higher resolution inset shows clearly that the electrodes are separated. Scale bar, 200 nm. (C) SEM image of nanotweezers after mounting two MWNT bundles on each electrode. Scale bar, 2  m.

Electromechanical response of the nanotube nanotweezers. (A through E). Dark-field optical micrographs of the nanotube arms at potentials of 0, 5, 7.5, 8.3, and 8.5 V, respectively. Scale bars, 1  m. The mechanical deflection of the nanotweezers in response to the bias voltage applied to the electrodes is shown.

Optical micrographs showing the sequential process of nanotweezer manipulation of polystyrene nanoclusters containing fluorescent dye molecules. (A)Approach of the nanotweezers to nanoclusters. (B)Alignment of the tweezer arms on a small cluster. A voltage was applied to nanotweezer arms on the nanocluster, (C and D) and then the nanotweezers and cluster were moved away from the sample support.