Dual sensing-actuation artificial muscle based on polypyrrole-carbon nanotube composite

Dual sensing artificial muscles based on conducting polymer are faradaic motors driven by electrochemical reactions, which announce the development of proprioceptive devices. The applicability of different composites has been investigated with the aim to improve the performance. Addition of carbon nanotubes may reduce irreversible reactions. We present the testing of a dual sensing artificial muscle based on a conducting polymer and carbon nanotubes composite. Large bending motions (up to 127 degrees) in aqueous solution and simultaneously sensing abilities of the operation conditions are recorded. The sensing and actuation equations are derived for incorporation into a control system.The research was supported by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641822

Properties of polypyrrole polyvinilsulfate films for dual actuator sensing systems

One of the challenges of modern science is the development of actuators able to sense working conditions while actuation, mimicking the way in which biological organs work. Actuation of those organs includes nervous (electric) pulses dense reactive gels, chemical reactions exchange of ions and solvent. For that purpose, conducting polymers are being widely studied. In this work the properties of self-supported films of the polypyrrole:polyvinilsulfate (PPy/PVS) blend polymer were assessed. X-ray photoelectron spectroscopy (XPS) studies show how during reduction / oxidation the polymer exchanges cations when immersed in a NaClO4 aqueous solution, revealing free positive charges in the electrolytic solution as the driving agents leading to the swelling/shrinking of the polymer. Eventually it is the phenomenon responsible of the actuation of the polymeric motors. Submitting the system to consecutive potential sweeps shows the reaction is really sensing the scan rate used in each cycle revealing that while actuating the system is actually sensing the electrochemical working conditions.The research was supported by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641822

Creeping and structural effects in Faradaic artificial muscles

Reliable polymeric motors are required for the construction of rising accurate robots for surgeon assistance. Artificial muscles based on the electrochemistry of conducting polymers fulfil most of the required characteristics, except the presence of creeping effects during actuation. To avoid it, or to control it, a deeper knowledge of its physicochemical origin is required. With this aim here bending bilayer tape/PPy-DBSH (Polypyrrole-dodecylbenzylsulphonic acid) full polymeric artificial muscles were cycled between −2.5 and 1 V in aqueous solutions with parallel video recording of the described angular movement. Coulo-voltammetric (charge-potential, QE), dynamo-voltammetric (angle-potential, αE), and coulo-dynamic (charge-angle, Qα) muscular responses corroborate that 10 % of the charge is consumed by irreversible reactions overlapping the polymer reduction at the most cathodic potentials. In parallel, the range of the bending angular movement (145°) shifts by 15° per cycle (creeping effect) pointing to the irreversible charge as possible origin of the irreversible swelling of the PPy-DBS film. Different slopes in the closed loop part of the QE identify the different reaction driven structural processes in the film: oxidation-shrinking, oxidation compaction, reduction-relaxation, reduction-swelling, and reduction-vesicle’s formation. Despite the irreversible charge fraction, the muscle motor keeps a Faradaic behaviour: described angles are linear functions of the consumed charge in the full potential range

Structural Electrochemistry from Freestanding Polypyrrole Films: Full Hydrogen Inhibition from Aqueous Solutions

Free-standing polypyrrole films, being the metal–polymer contact located several millimeters outside the electrolyte, give stationary closed coulovoltammetric (charge/potential) loop responses to consecutive potential sweeps from –2.50 V to 0.65 V in aqueous solutions. The continuous and closed charge evolution corroborates the presence of reversible film reactions (electroactivity), together high electronic and ionic conductivities in the full potential range. The closed charge loop demonstrates that the irreversible hydrogen evolution is fully inhibited from aqueous solutions of different salts up to –2.5 V vs Ag/AgCl. The morphology of the closed charge loops shows abrupt slope changes corresponding to the four basic components of the structural electrochemistry for a 3D electroactive gel: reduction-shrinking, reduction-compaction, oxidation-relaxation, and oxidation-swelling. Freestanding films of conducting polymers behave as 3D gel electrodes (reactors) at the chain level, where reversible electrochemical reactions drive structural conformational and macroscopic (volume variation) changes. Very slow hydrogen evolution is revealed by coulovoltammetric responses at more cathodic potentials than –1.1 V from strong acid solutions, or in neutral salts self-supported blend films of polypyrrole with large organic acids. Conducting polymers overcome graphite, mercury, lead, diamond, or carbon electrodes as hydrogen inhibitors, and can compete with them for some electro-analytical and electrochemical applications in aqueous solutions

Biomimetic reactions in conducting polymers for artificial muscles: sensing working conditions

IIn the dense gel that is the intracellular matrix forming part of living cells electrochemical reactions take place provoking the interchange of ions and water with the surroundings. Systems containing conducting polymers mimic this feature of biological organs. In particular, conducting polymers are being studied as dual sensing-actuating reactive materials giving new multifunctional sensing-actuators, which allow the construction and theoretical description of artificial proprioceptive devices. Here films of polypyrrole/dodecyl benzene sulfonate (PPy-DBS) coating a platinum electrode were submitted to potential sweeps at different sweep rates in order to explore if the polymer reaction senses the working electrochemical conditions. The effective consumed electrical energy per cycle follows a fast decrease when the scan rate increases described by the addition of two exponential sensing functions. Moreover, the variation of the hysteresis from the parallel charge/potential loop with the scan rate is also described by the addition of two exponential functions. In both cases the exponential functions fitting results at low scan rates are related to reaction-driven conformational movements of the polymer chains, being closer to biochemical conformational and allosteric sensors. The second exponential functions fitting results at high scan rates are related to diffusion kinetic control, being closer to present electrochemical sensors.The research was supported by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641822

Biomimetic polypyrrole based all three-in-one triple layer sensing actuators exchanging cations†

Simultaneous actuation and sensing properties of a triple layer actuator interchanging cations are presented for the first time. Thick polypyrrole (pPy)/dodecylbenzenesulfonate (DBS) films (36 mm) were electrogenerated on stainless steel electrodes. Sensing characteristics of pPy-DBS/tape/pPy-DBS triple layer artificial muscle were studied as a function of electrolyte concentration, temperature and driving current using lithium perchlorate (LiClO4) aqueous solution as electrolyte. The chronopotentiometric responses were studied by applying consecutive square waves of currents to produce angular movements of 45 by the free end of the triple layer. The evolution of the muscle potential (anode film versus cathode film) during current flow is a function of the studied chemical and physical variables. The electrical energy consumed to describe a constant angle is a linear function of the working temperature or of the driving electrical current, and a double logarithmic function of the electrolyte concentration. Those are the sensing functions. The cation exchanging bending triple layer actuator senses the working conditions. Similar sensing functions were described in the literature for devices interchanging anions. Irrespective of the reaction mechanism, a single electrochemo–mechanical device comprised of two reactive polymer electrodes (oxidation film and reduction film) works simultaneously as both sensor and actuator (self-sensing actuators). These are the general sensing properties of dense and biomimetic reactive gels of conducting polymers. Thus, any reactive device based on the same type of materials and reactions (batteries, smart windows, actuators, electron–ion transducers) is expected to sense surrounding conditions, as biological organs do

Preparación y aplicación de músculos artificiales, actuadores y dispositivos poliméricos para desplazamientos longitudinales y de válvula.

Número de publicación: 2 233 171 Número de solicitud: 200300800Esta invención describe un dispositivo capaz de transformar los movimientos angulares, característicos de los músculos artificiales basados en polímeros conductores, en movimientos longitudinales lineales, bajo el estímulo de una corriente eléctrica. Como en los músculos artificiales constituyentes estos dispositivos son totalmente poliméricos y están formados por bicapas, o tricapas de polímeros conductores electrónicos intrínsecos y de polímeros no conductores, adherentes y flexibles. El movimiento lineal del dispositivo, se consigue por combinación de dos o más elementos básicos: bicapas o tricapas, lo que da lugar, así mismo, a dispositivos de apertura y cierre, como pueden ser válvulas, totalmente poliméricas. Estos dispositivos pueden abarcar diferentes sectores de la técnica como son: Mecánica y micro-mecánica: posicionadores, actuadores, elevadores, mecanismos reversibles, elementos de sujeción. Microelectrónica: sensores, contactores, disparadores. Biomedicina: catéteres, micro-separadores, micro-obturadores, micro-válvulas. Dispositivos similares se pueden construir con cualquier tipo de actuador polimérico y electromecánico basados en mecanismos: electroquímicos, electroforéticos, electroosmóticos, de transferencia y migración iónica, piezoeléctricos o electrostrictivos (fenómenos electromecánicos de primer orden o de segundo orden).Universidad Politécnica de Cartagen

Self-supported polypyrrole/polyvinylsulfate films: electrochemical synthesis, characterization, and sensing properties of their redox reactions

Thick films of polypyrrole/polyvinylsulfate (PPy/PVS) blends were electrogenerated on stainless‐steel electrodes under potentiostatic conditions from aqueous solution. The best electropolymerization potential window was determined by cyclic voltammetry. After removing the film from the back metal, self‐supported electrodes were obtained. Voltammetric, coulovoltammetric, and chronoamperometric responses from a LiClO4 aqueous solution indicated the formation of an energetically stable structure beyond a reduction threshold of the material. Its subsequent oxidation required higher anodic voltammetric overpotentials or longer chronoamperometric oxidation times. This structure was attributed to the formation of lamellar or vacuolar structures. X‐ray photoelectron spectroscopy analysis of the films under different oxidations states revealed that the electrochemical reactions drive the reversible exchange of cations between the film and the electrolyte. The electrical energy and the charge consumed by the reversible reaction of the film under voltammetric conditions between the constant potential limits are a function of the potential scan rate, that is, they sense the working electrochemical conditions.This project was supported by the Marie‐Sklodowska‐Curie Innovative Training Network MICACT‐H2020‐MSCA‐ITN‐2014 and by the Séneca Foundation project 19253/PI/14

Reacción Electroquímica de Polietilendioxitiofeno (PEDOT). Metodología para el cálculo de parámetros cinéticos

El propósito de desarrollar modelos cinéticos es el de obtener las constantes del proceso de tal manera que permita una mejora en las posibles aplicaciones (actuadores, membranas o dispositivos electrocrómicos).Agradecimientos: trabajo financiado por el MEC. Proyecto CTQ2005-00908 (grupo D023-01) y (CTQ2006-26262-E)