Electrochemomechanical Devices Based on Conducting Polymers

Abstract

IntroductionIn general movement is an intrinsic property of living creatures. It occurs at different structural levels including ion transfer through membranes, separation of replicated chromosomes, beating of cilia and flagella or, the most common, contraction of muscles. Those contractions enable the organism to carry out organized and sophisticated movements such as walking, running, flying, swimming, breathing, digesting foods, etc., as well as generating mechanical energy.Great strides have been made during human evolution in developing biological systems. Among these, muscles are elegant devices developed through thousand of years of evolution to transform chemical energy into mechanical energy and heat. This transformation is triggered by an electric pulse arriving from the brain through nerves, which promotes an increase of Ca+ 2 inside the myofibrils from 10-7 to 10-3 mollI. The increase of the ionic concentration promotes conformational changes in the troponimtropomyosin system allowing muscle contraction [1]. The energy required for these conformational changes is generated by ATP hydrolysis, this being the bonding ion between myosin heads and actin filaments. ATP is restored from ADP through the glucose cycle. All those processes take place in aqueous media. A muscle can be considered as an electro-chemo-mechanical actuator.Thus macroscopic movements developed by a muscle are generated by molecular movements occurring in biological macromolecules, and several points can be stressed: -A muscle is a complex system where water, ions, macromolecules, and small organic molecules play important roles. -A nervous pulse promotes ionic interchanges between every myofibril and the surroundings in a few microseconds. -The free energy of ATP hydrolysis drives conformational changes in the myosin head, resulting in the net movement of myosin along the actin filament. -The movement occurs through the formation of complexes between two macromolecules (myosin and actin) and an ion,ATP, and the subsequent dissociation of those complexes with formation of ADP. -The high energetic content of ATP is restored from the ADP by transferring energy from glycolysis. -Muscles work at constant temperature and the heat generated during those transformations by entropic requirements has to be eliminated. Y. Osada et al. (eds.), Polymer Sensors and Actuators

Artificial muscles based on conducting polymers

“…This relation does not depend either on electrolyte concentration or on electrical conditions. Also an increase of the electrolyte concentration promotes an easier entrance of anions into the polymer structure [113][114][115].…”

Understanding the structural changes that take place in a polypyrrole film during its oxi-reduction process: a molecular dynamics simulation study

“…[1][2][3][4][5] In this regard, a wide number of conducting polymers, blends and composites have been synthesized with the goal of improving the physical properties properties of these polymers focused on their specific applications. 6,7 However, among other conducting polymers, polypyrrole has been one of the most widely studied, mainly due to its excellent electrical response and good stability in both, organic and inorganic solvents where the oxi-reduction process takes place.…”

Polypyrrole actuators for micropump applications

“…ICPs are attractive materials due to their low voltage operation, light weight, freedom in design of the polymeric matrix and ease of deposition in patterns 4,[8][9][10] . The actuation within ICPs results from the volume change arising from the movement of charge balancing solvated counterions in and out of the polymer matrix, along with changes in the conformation of the polymer backbone 2 .…”