Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical–based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology

Low efficiencies and costly electrode materials have limited harvesting of thermal energy as electrical energy using thermo-electrochemical cells (or "thermocells"). We demonstrate thermocells, in practical configurations (from coin cells to cells that can be wrapped around exhaust pipes), that harvest low-grade thermal energy using relatively inexpensive carbon multiwalled nanotube (MWNT) electrodes. These electrodes provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency. Thermocell efficiency is further improved by directly synthesizing MWNTs as vertical forests that reduce electrical and thermal resistance at electrode/substrate junctions. The efficiency of thermocells with MWNT electrodes is shown to be as high as 1.4% of Carnot efficiency, which is 3-fold higher than for previously demonstrated thermocells. With the cost of MWNTs decreasing, MWNT-based thermocells may become commercially viable for harvesting low-grade thermal energy.

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Carbon nanotubes are of significant interest due to their unique properties and potential applications. [1][2][3][4] We are interested in using single-walled carbon nanotubes (SWNTs) as an electrode material suitable for electromechanical actuators. 5 Such application requires a good understanding of the electrochemical properties of SWNTs.In this initial report, we describe some of the basic electrochemical characteristics of sheets of SWNTs. These sheets, called nanotube paper (NTP) due to their appearance, consist of SWNT bundles joined by mechanical entanglement and van der Waals interactions. The NTP shows high porosity and large surface area. 5,6 It is generally considered 1-6 that in the material used the nanotubes ends are closed and that the interstitial spaces between individual nanotubes inside a bundle are not accessible to the electrolyte. Consequently, the pores responsible for most of the surface area correspond to the void spaces between bundles. The techniques utilized for the characterization of the NTP were cyclic voltammetry, electrochemical impedance spectroscopy, and electrochemical quartz crystal microgravimetry. Several aqueous and nonaqueous electrolytes were evaluated.Experimental Chemicals and materials.-All solutions were prepared using Milli-Q deionized water. The SWNTs dispersed in water were obtained from Tubes@Rice (Rice University) with a purity better than 90%. The material consists of hexagonally packed bundles of nanotubes 1.2-1.4 nm diam. Each bundle consists of about 30 nanotubes and is 10 nm average diam and several micrometers long. 6

The fabrication of single‐walled carbon nanotube (CNT) fibers containing (salmon) DNA has been demonstrated. The DNA material has been found to be adequate for dispersing relatively large concentrations (up to 1 % by weight) of carbon nanotubes. These dispersions are better suited for fiber spinning than previously studied dispersions based on conventional surfactants, such as sodium dodecyl sulfate (SDS). The DNA‐containing fibers were less conductive than the fibers based on SDS, but they were significantly stronger. Considerably increased conductivity was obtained by thermally annealing the CNT/DNA fibers, a process accompanied by a loss in mechanical strength. Smaller improvements in conductivity could be introduced by annealing the carbon nanotubes before fiber production, with no alteration of the fiber mechanical properties. Those CNT/DNA fibers that were mechanically strong and conductive also exhibited good electrochemical behavior and useful capacitance values (up to 7.2 F g–1).

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