Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles

Abstract

Improved electrically powered artificial muscles are needed for generating force, moving objects, and accomplishing work. Carbon nanotube aerogel sheets are the sole component of new artificial muscles that provide giant elongations and elongation rates of 220% and (3.7 x 10(4))% per second, respectively, at operating temperatures from 80 to 1900 kelvin. These solid-state-fabricated sheets are enthalpic rubbers having gaslike density and specific strength in one direction higher than those of steel plate. Actuation decreases nanotube aerogel density and can be permanently frozen for such device applications as transparent electrodes. Poisson's ratios reach 15, a factor of 30 higher than for conventional rubbers. These giant Poisson's ratios explain the observed opposite sign of width and length actuation and result in rare properties: negative linear compressibility and stretch densification.

Modelling negative linear compressibility in tetragonal beam structures

“…It is still an early stage for applications, but it is possible to envisage composites with zero compressibility, or pressure driven actuators as in nanotubes based artificial muscles (Aliev et al, 2009) (Nye, 1985), but tenuous evidence to the contrary exists where a strain dependant NVC (negative volume compressibility) has been encountered in foams (Lakes and Drugan, 2002) and in networks of bi-materials where the hydrostatic pressure was subjected to all interior and exterior faces . However negative values of the other two properties have unquestionably been identified in crystals.…”

Hygromorphic actuator from a metal oxide film driven by a nano-capillary forest structure

“…Figure 4b compares the estimated energy densities and strain responses of the TNF film with typical values reported for materials frequently used or studied in the context of actuators and stimuli-responsive materials. [20][21][22][23][24] At this point, even though this TNF actuator has a much lower energy density than a shape memory alloy, it still shows a relatively high energy density compared to other actuators with sustainability and repeatability. Since this actuator uses a new hygromorphic actuating mechanism, it could be a useful actuator once the obstacles, such as response time and actuation speed, are solved.…”

“…In fact, onlỹ 15 mg of the titanium oxide nano-capillary films generated a larger force than most other actuating devices on a per mass basis. [20][21][22][23][24] Because the strain energy varies throughout a body, it is convenient to use the concept of strain energy density, which is a measure of how much energy is stored in small-volume elements throughout a material. To calculate the energy density of the free-standing TNF film, we assumed that the film is a uniform geometry in the form of an end-loaded cantilever of length L and calculated the strain energy for normal stresses acting in the elastic material upon deformation by a steadily increasing force F. The work done in extending the cantilever by a small amount, dx, is stored as elastic strain energy U, given as U = Fdx.…”

Congo Red Interactions with Single-Walled Carbon Nanotubes

“…A particularly interesting is their use in the field of biomedicine: in biosensors [6,7], medical diagnostics [8,9], transplantology [10,11], tissue engineering [12] or in pharmacology -including the field of targeted therapies [13][14][15][16].…”