There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Carbon materials for the electrochemical storage of energy in capacitors

Electrical actuators were made from films of dielectric elastomers (such as silicones) coated on both sides with compliant electrode material. When voltage was applied, the resulting electrostatic forces compressed the film in thickness and expanded it in area, producing strains up to 30 to 40%. It is now shown that prestraining the film further improves the performance of these devices. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers using biaxially and uniaxially prestrained films. The strain, pressure, and response time of silicone exceeded those of natural muscle; specific energy densities greatly exceeded those of other field-actuated materials. Because the actuation mechanism is faster than in other high-strain electroactive polymers, this technology may be suitable for diverse applications.

http://science.sciencemag.org/content/sci/287/5454/836.full.pdf

High-Speed Electrically Actuated Elastomers with Strain Greater Than 100%

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.

/pdf/carbon-nanotube-actuators-1chbcyw6t7.pdf

Carbon Nanotube Actuators

The widespread use of controlled molecular-level motion in key natural processes suggests that great rewards could come from bridging the gap between the present generation of synthetic molecular systems, which by and large rely upon electronic and chemical effects to carry out their functions, and the machines of the macroscopic world, which utilize the synchronized movements of smaller parts to perform specific tasks. This is a scientific area of great contemporary interest and extraordinary recent growth, yet the notion of molecular-level machines dates back to a time when the ideas surrounding the statistical nature of matter and the laws of thermodynamics were first being formulated. Here we outline the exciting successes in taming molecular-level movement thus far, the underlying principles that all experimental designs must follow, and the early progress made towards utilizing synthetic molecular structures to perform tasks using mechanical motion. We also highlight some of the issues and challenges that still need to be overcome.

Synthetic molecular motors and mechanical machines.

Electrochemomechanical properties from a bilayer: polypyrrole / non-conducting and flexible material — artificial muscle

Biomimetic electrochemistry from conducting polymers. A review: Artificial muscles, smart membranes, smart drug delivery and computer/neuron interfaces

Artificial Muscles with Tactile Sensitivity

Humans try to use their technology to reproduce devicesthat have been optimized by nature over thousands ofyears during the evolution of living creatures. Among thesesystems, muscles are elegant devices developed by evolu-tion to transform chemical energy to mechanical energyand heat at constant temperature, far away from the limita-tions imposed by Carnot’s theorem on our thermal motors.Proteins (polymers), small organic molecules, and inorgan-ic and organic ions in aqueous media constitute the mixedmaterials chosen by nature from which to construct mus-cles. The increase in Ca

Soft and wet conducting polymers for artificial muscles.

A simple model of polymeric relaxation, associated with the electrochemical switching of polypyrrole films between their reduced (insulating) and oxidized (electronically conducting) states, offers a reasonably precise description of the form of chronoamperograms obtained after previous subjection of the polymer film to cathodic potentials (which control the compactness of the neutral polymer) for long periods of time. The opening of the structure driven by the anodic potential is not uniform:  nucleation of conducting zones inside the neutral polymer and their overlap at long times of anodic polarization are taken into account in the model. Diffusion of counterions from the solution across the oxidized zones is also included. The definition of a relaxation time (depending on both cathodic and anodic overpotentials and on temperature), and the inclusion of nucleation and diffusion processes, allows a theoretical simulation of chronoamperograms, in good agreement with experimental results from potential st...

Toribio F. Otero

Papers

Electrochemomechanical properties from a bilayer: polypyrrole / non-conducting and flexible material — artificial muscle

Biomimetic electrochemistry from conducting polymers. A review: Artificial muscles, smart membranes, smart drug delivery and computer/neuron interfaces

Artificial Muscles with Tactile Sensitivity

Soft and wet conducting polymers for artificial muscles.

Reinterpretation of Polypyrrole Electrochemistry after Consideration of Conformational Relaxation Processes