Photoactuation in nafion-carbon nanotube bilayer composites

Kinetics of Photoactuation in Single Wall Carbon Nanotube−Nafion Bilayer Composite

“…Bilayer cantilevers were formed by airbrushing a suspension of SWNTs in chloroform (0.8 mg/mL) onto a Nafion film. , Typically, the Nafion had dimensions of 13 mm length, 1 mm width, and 50 μm thick while the SWNT layer was 10−20 μm thick. As we reported previously, , the photoactuation is reversible and the displacement is always in the direction of the Nafion layer, independent of the direction of the light. No photoactuation is observed for pure SWNT films of comparable thickness nor when the substrate is changed to polyethylene.…”

“…No photoactuation is observed for pure SWNT films of comparable thickness nor when the substrate is changed to polyethylene. The magnitude of the photoactuation follows the absorption spectrum of the semiconducting SWNTs and is linear in the light intensity. , Finally, when graphite is coated (also by airbrushing) onto Nafion, no photoactuation is observed.…”

“…The mechanism of the photoactuation must include an initiation caused by light, a humidity-dependent fast step that provides mechanical motion in the opposite direction of the net response, and include, at minimum, a conformational change in the water structure in the Nafion. We have previously , demonstrated that the magnitude of the photoactuation parallels the absorption of the semiconducting SWNTs, suggesting that the initial photoexcitation creates surface charges (photoelectrons) in the SWNTs leading to polarization of the Nafion/SWNT interface. The electric field induces migration of hydrated hydrogen ions and water molecules toward the interface.…”

“…8 The photoactuation in the SWNTs was attributed to electrostatic interaction within the network bundle. The optomechanical response can be amplified by coating the SWNTs onto Nafion 9,10 or other polymers. 11,12 Multiwalled carbon nanotubes blended into polydimethylsiloxanes also demonstrate substantial photoactuation.…”

“…The photoactuation in the SWNTs was attributed to electrostatic interaction within the network bundle. The optomechanical response can be amplified by coating the SWNTs onto Nafion , or other polymers. , Multiwalled carbon nanotubes blended into polydimethylsiloxanes also demonstrate substantial photoactuation. − The mechanism of the photoactuation in these systems is under some debate. Electrostatic effects are thought to be more important than heating. − In the case of the Nafion substrate, the migration of water and hydrated hydrogen ions in the polymer under the influence of a light-created interfacial electrical field was proposed as the primary mechanism. , …”