NASA’s Langley Research Center offers an all-organic electroactive device system fabricated with single-wall carbon nanotubes (SWCNT). The enhanced design offers higher electroactive performance in comparison with conventional electroactive device systems fabricated with metal electrodes or other conducting polymers. The new structure allows for significant improvement of the electroactive strain due to relief of the constraint on the electroactive layer. It exhibits superb actuation properties and can withstand high temperatures with improved mechanical integrity and chemical stability. In addition, the electroactive device can be made transparent, allowing for use in optical devices. NASA is seeking development partners and potential licensees.
Commonly used metal electrodes such as silver and gold tend to constrain displacement (elongation or contraction) of an electroactive polymer at the interface. The actual output strain of the metal devices is smaller than what they can intrinsically provide. Many alternative electrode materials that could relieve the strain of movement, such as conducting polymers, have been proposed, but they are usually not thermally stable enough for most applications.
The innovation from Langley is a new method for creating the all-organic flexible SWCNT film electrode, which has high conductivity and good thermal stability. SWCNTs are first dispersed into a solution and then filtered onto the surface of a porous, anodized-alumina membrane to form a SWCNT film. The SWCNT film is separated by breaking the brittle alumina membrane and delaminating the film. Adjusting the concentration and quantity of SWCNT solution varies the SWCNT film’s width and thickness. The SWCNT film has the potential to be made thin enough to be transparent.
The SWCNT film is then used to form the all-organic electroactive device system that can be used as an actuator. An electroactive polymer sandwiched between the SWCNT electrodes is fabricated by pressing the layers together at 600, 3000, and 6000 psi. By controlling the fabrication pressure, the level of physical properties, which can match the electroactive polymers, can be adjusted and tailored appropriately.
Potential applications include optical devices; electromechanical energy conversion; medical devices such as prosthetics, artificial muscles, artificial diaphragms and valves, active Braille displays, and chiropractic patches; sonar; and transducers. The technology can also be used by design engineers to reduce vibration and control noise due to the flexibility of a material.