Artificial molecular muscles

It is worth noting that no alignment of the rotaxane molecules with respect to the cantilevers is required to observe a bending effect because only the component of the contraction that is parallel to the long axis of the cantilever contributes effectively to the bending. 

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Valero, L. Arias-Pardilla, J. Cauich-Rodrfguez, J. Smit, M. A. Otero, T. R Characterization of the movement of polyp5UTole-dodecylbenzenesulfonate-perchlorate/tape artificial muscles. Faradaic control of reactive artificial molecular motors and muscles. Electrochim. Acta 2011,10, 3721-3726. 

A molecular machine, a machine at the molecular level, is defined as a discrete number of molecular components that perform mechanical-like movements (output) in response to specific stimuli (input). Molecular machines include both naturally occurring devices found in biological systems and artificial molecular machines. There are many molecular machines in biological systems. Among the most prominent examples of molecular machines in living organisms are the muscle linear and ATPase rotary motors. In order to develop artificial machinery, scientists have constructed a variety of molecular and supramolecular systems with differences in shape, switching processes, or movements... 

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

The objective of Materials Chemistry is to provide an overview of the various types of materials, with a focus on synthetic methodologies and relationships between the structure of a material and its overall properties. Each chapter will feature a section entitled Important Materials Applications that will describe an interesting current/future application related to a particular class of material. Topics for these sections include fuel cells, depleted uranium, solar cells, self-healing plastics, and molecular machines e.g., artificial muscles). 

Transfer of calcium cations (Ca2 + ) across membranes and against a thermodynamic gradient is important to biological processes, such as muscle contraction, release of neurotransmitters or biological signal transduction and immune response. The active transport can be artificially driven (switched) by photoinduced electron transfer processes (Section 6.4.4) between a photoactivatable molecule and a hydroquinone Ca2 + chelator (405) (Scheme 6.194).1210 In this example, oxidation of hydroquinone generates a quinone to release Ca2+ to the aqueous phase inside the bilayer of a liposome, followed by reduction of the quinone back to hydroquinone to complete the redox loop, which results in cyclic transport of Ca2 +. The electron donor/acceptor moiety is a carotenoid porphyrin naphthoquinone molecular triad (see Special Topic 6.26). 

Natural polymers remain an inspiration and provide considerable stimulation for researchers of artificial intelligent materials and systems. For example, antibodies and enzymes provide the molecular recognition capabilities used so magnificently by nature. Macromolecules are also the basis of that most useful of actuator systems muscles. Furthermore, it is the generation and transmission of electrical signals that regulate the processes behind the formation and operation of these biosystems. 

Furthermore, LCEs have been prepared by block copolymerization and hydrogen bonds (Cui et al., 2004 Li et al., 2004). Li et al. (2004) proposed a musclelike material with a lamellar structure based on a nematic triblock copolymer (Components 8a-c, Fig. 3.10). The material consists of a repeated series of nematic (N) polymer blocks and conventional rubber (R) blocks. The synthesis of block copolymers with well-defined structures and narrow molecular-weight distributions is a crucial step in the production of artificial muscle based on triblock elastomers. Talroze and coworkers studied the structure and the alignment behavior of LC networks stabilized by hydrogen bonds under mechanical stress (Shandryuk et al., 2003). They synthesized poly[4-(6-acryloyloxyhexyloxy)benzoic acid], which... 

Otero, T.E, H. Grande, and J. Rodriguez. 1996. Reversible electrochemical reactions in conducting polymers a molecular approach to artificial muscles. J Phys Org Chem 9 381. 

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