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

SEMICONDUCTORES ORGÁNICOS

SÓLO VISIÓN PROYECTABLE

INVESTIGACIÓN Y COMUNICACIÓN CIENTÍFICA

SÓLO VISIÓN PROYECTABLE

Caracterización de músculos artificiales con capacidades sensores/actuadores e intercambio mayoritario de cationes

Mención Europeo / Mención Internacional: Concedido[SPA] En esta tesis se describe la síntesis electroquímica de películas gruesas de polipirrol/DBS. Las películas se despegan del electrodo y se usan como electrodos autosoportados, para construir bicapas (pPy/DBS-cinta adhesiva) o tricapas (pPy/DBS-cinta-pPy/DBS). El comportamiento electroquímico de la película polimérica, utilizada como electrodo autosoportado, es caracterizado mediante diferentes técnicas electroquímicas. Repitiendo la caracterización variando ahora la concentración del medio, la temperatura de trabajo o la corriente de oxidación/reducción se investigó y cuantificó la capacidad de las reacciones del material para sentir (capacidad sensora) las condiciones de trabajo. Se realiza la caracterización electroquímica y del movimiento de bicapas pPy/DBS-cinta (músculo artificial de bicapa), que es registrado en video. De los video-frames se obtiene la evolución del ángulo descrito por el músculo con el potencial aplicado o con la carga consumida. Se confirma así que la reacción que provoca el movimiento en el rango completo de potenciales estudiados origina la expulsión de cationes desde el polímero conductor durante su oxidación y su entrada durante la reducción. El actuador polimérico es un motor faradaico controlado por la reacción electroquímica que origina del movimiento: la velocidad angular es una función lineal (control sencillo de la velocidad) de la corriente eléctrica aplicada y el ángulo descrito por el movimiento es una función lineal de la carga consumida (también provee otro control sencillo del desplazamiento). A potenciales muy catódicos se produce algo de hidrógeno, provocando un desplazamiento (creeping) del movimiento en cada ciclo: hay que evitarlo porque complica el control lineal del desplazamiento. Los desplazamientos angulares del músculo consumiendo la misma carga en disoluciones acuosas de sales con distintos cationes permitió cuantificar el número de moléculas de agua intercambiado por unidad de reacción (o por catión) durante la reacción. La evolución del potencial muscular y de la energía eléctrica consumida durante la reacción siente las condiciones energéticas de trabajo: energía química (concentración del electrolito), energía térmica (temperatura de trabajo) o energía eléctrica (corriente aplicada). El motor polimérico siente, mientras trabaja, sus condiciones de trabajo. El dispositivo imita a los músculo hápticos de los seres vivos. Las curvas de calibración para los diferentes sensores han sido obtenidas. Las tricapas (pPy/DBS-cinta-pPy/DBS) también se comportaron como músculos faradaicos que sienten, mientras trabajan, las condiciones térmicas, químicas, mecánicas o eléctricas. En un dispositivo trabajan, simultáneamente, un motor y cuatro sensores. Toda la información actuadora (corriente y carga) y sensora (potencial y energía eléctrica) está contenida, simultáneamente, en los dos únicos cables de conexión. El sistema potenciostato-cables-músculo-celda electroquímica actúa como el sistema natural celebro-nervios-músculos. [ENG] Over the past decade scientific research has been looking for new biomimetic materials able to imitate human organs behaviour, in such a way that is possible to apply them on different technologies: low cost ones, scalable ones, low energy consumption ones and on those with high potentialities in areas such as health, robotics, artificial nerves and muscles, among others. Most of the studied materials mimic the extracellular matrix (ECM) of living cells and its physical functions. Now, and for the first time, conducting polymers, and other electroactive materials exchange ions and water through electrochemical reactions: the material becomes a dense electroactive gel. The content of mentioned gel and the reactions happening in it mimic, by the first time in the history of science, the composition (in its simplest expression) and reactions taking place in the reactive intracellular matrix of the functional cells of living beings. During the chemical reactions (oxidation or reduction) the gel relative composition (polymer-ion-water) shifts, in a reversible way, by several orders of magnitude. Along with it several composition-dependent properties of the material change simultaneously. The reversible variation of the material volume driven by the reactions mimics the natural muscles behaviour: artificial polymeric muscles, or polymeric electrochemical actuators, based on this property are being developed. With the material composition the consumed energy change as a function thermal, chemical or mechanical conditions. This fact is used for the development of sensors and biosensors. The material volume and the material potential shift, simultaneously, during the reaction. Here the possibility to develop dual sensing-actuators is explored: two elements working concurrently in the same, physically uniform, device mimicking haptic muscles. In this thesis the electrochemical synthesis of thick polypyrrole/DBS films is described. The electrochemical behaviour of the polymer film, used as a self-supported electrode, is characterized assuming the exchange of cations during its oxidation/reduction. For the electrochemical characterization of biomimetic films of polypyrrole/DBS, different electrochemical techniques are used and under different experimental conditions with the view to understanding the sensing potentialities of the material reactions. The study and electrochemical characterization of the motion of pPy/DBS//tape bilayer bending actuators corroborates that the reaction is driven by the expulsion of cations from the conducting polymer to the electrolyte during oxidation and its entrance during reduction, in the full potential range studied. The actuator is a faradaic device controlled by the electrochemical reaction driving the movement: the rate of the angular movement is a linear function (easy control of the velocity) of the applied current and the described angle by the displacement is a linear function of the consumed charge (it also provides another easy control of the displacement) The evolution of the muscle potential and that of the consumed electrical energy during the reaction senses the energetic working conditions: chemical energy (electrolyte concentration), thermal energy (working temperature) or electric energy (applied current). The polymeric motor senses, while working, environmental conditions. The sensing calibration curves were attained for the different sensors. They have been constructed and characterized triple-layer artificial muscles pPy/DBS//Tape//pPy/DBS, corroborating again the exchange of cations during the reaction, the faradic nature of the device and the ability of the device to sense, while moving, its environmental working conditions mimicking natural haptic muscles. The actuator (current and charge) and sensing (muscle potential and involved energy) signals are simultaneously present in only two connecting wires, mimicking brain-muscle intercommunication. The study of polymeric materials with cationic and/or ionic exchange opens the possibility of working in a future, using also anion-exchange materials, to develop new soft, wet, biomimetic and multifunctional tools and robots. Ionic, chemical, thermal and mechanical signals can be transformed into electrical ones and the involved information is transported using just two wires, simplifying in that way their connection to computers: the design of devices and robots having them heralds a more efficient technology.[ENG] Over the past decade scientific research has been looking for new biomimetic materials able to imitate human organs behaviour, in such a way that is possible to apply them on different technologies: low cost ones, scalable ones, low energy consumption ones and on those with high potentialities in areas such as health, robotics, artificial nerves and muscles, among others. Most of the studied materials mimic the extracellular matrix (ECM) of living cells and its physical functions. Now, and for the first time, conducting polymers, and other electroactive materials exchange ions and water through electrochemical reactions: the material becomes a dense electroactive gel. The content of mentioned gel and the reactions happening in it mimic, by the first time in the history of science, the composition (in its simplest expression) and reactions taking place in the reactive intracellular matrix of the functional cells of living beings. During the chemical reactions (oxidation or reduction) the gel relative composition (polymer-ion-water) shifts, in a reversible way, by several orders of magnitude. Along with it several composition-dependent properties of the material change simultaneously. The reversible variation of the material volume driven by the reactions mimics the natural muscles behaviour: artificial polymeric muscles, or polymeric electrochemical actuators, based on this property are being developed. With the material composition the consumed energy change as a function thermal, chemical or mechanical conditions. This fact is used for the development of sensors and biosensors. The material volume and the material potential shift, simultaneously, during the reaction. Here the possibility to develop dual sensing-actuators is explored: two elements working concurrently in the same, physically uniform, device mimicking haptic muscles. In this thesis the electrochemical synthesis of thick polypyrrole/DBS films is described. The electrochemical behaviour of the polymer film, used as a self-supported electrode, is characterized assuming the exchange of cations during its oxidation/reduction. For the electrochemical characterization of biomimetic films of polypyrrole/DBS, different electrochemical techniques are used and under different experimental conditions with the view to understanding the sensing potentialities of the material reactions. The study and electrochemical characterization of the motion of pPy/DBS//tape bilayer bending actuators corroborates that the reaction is driven by the expulsion of cations from the conducting polymer to the electrolyte during oxidation and its entrance during reduction, in the full potential range studied. The actuator is a faradaic device controlled by the electrochemical reaction driving the movement: the rate of the angular movement is a linear function (easy control of the velocity) of the applied current and the described angle by the displacement is a linear function of the consumed charge (it also provides another easy control of the displacement) The evolution of the muscle potential and that of the consumed electrical energy during the reaction senses the energetic working conditions: chemical energy (electrolyte concentration), thermal energy (working temperature) or electric energy (applied current). The polymeric motor senses, while working, environmental conditions. The sensing calibration curves were attained for the different sensors. They have been constructed and characterized triple-layer artificial muscles pPy/DBS//Tape//pPy/DBS, corroborating again the exchange of cations during the reaction, the faradic nature of the device and the ability of the device to sense, while moving, its environmental working conditions mimicking natural haptic muscles. The actuator (current and charge) and sensing (muscle potential and involved energy) signals are simultaneously present in only two connecting wires, mimicking brain-muscle intercommunication. The study of polymeric materials with cationic and/or ionic exchange opens the possibility of working in a future, using also anion-exchange materials, to develop new soft, wet, biomimetic and multifunctional tools and robots. Ionic, chemical, thermal and mechanical signals can be transformed into electrical ones and the involved information is transported using just two wires, simplifying in that way their connection to computers: the design of devices and robots having them heralds a more efficient technology.Universidad Politécnica de CartagenaPrograma Oficial de Doctorado en Electroquímica. Ciencia y Tecnologí

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 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

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

Sensing and Tactile Artificial Muscles from Reactive Materials

Films of conducting polymers can be oxidized and reduced in a reversible way. Any intermediate oxidation state determines an electrochemical equilibrium. Chemical or physical variables acting on the film may modify the equilibrium potential, so that the film acts as a sensor of the variable. The working potential of polypyrrole/DBSA (Dodecylbenzenesulfonic acid) films, oxidized or reduced under constant currents, changes as a function of the working conditions: electrolyte concentration, temperature or mechanical stress. During oxidation, the reactive material is a sensor of the ambient, the consumed electrical energy being the sensing magnitude. Devices based on any of the electrochemical properties of conducting polymers must act simultaneously as sensors of the working conditions. Artificial muscles, as electrochemical actuators constituted by reactive materials, respond to the ambient conditions during actuation. In this way, they can be used as actuators, sensing the surrounding conditions during actuation. Actuating and sensing signals are simultaneously included by the same two connecting wires

Las Metodologías de la Auditoría Informática y su relación con Buenas Prácticas y Estándares

Las Auditorías Informáticas que se realizan en las organizaciones empresariales deben utilizar metodologías de apoyo, sin embargo, no existe una metodología única o una que sea reconocida de manera generalizada, su uso depende de la experiencia del auditor y del conocimiento de esta. Varios autores proponen metodologías de Auditoría Informática, y si bien, existen similitudes, se requiere complementarlas con buenas prácticas y estándares mundialmente aceptados. Estos apoyarían su uso en ¿cómo cumplir con los aspectos solicitados?, el fin es robustecerlas y minimizar la parte subjetiva que tienen de manera general las Auditorías, al ser ejecutadas. El objetivo de este artículo es realizar una revisión y descripción de las buenas prácticas para la gestión de las Tecnologías de Información que sirven para fortalecer las metodologías de las Auditorias Informáticas

Los músculos artificiales son motores eléctricos que sienten las condiciones de trabajo

Los actuadores de bicapa polipirrol-DBS-CI04-//polímero no conductor se comportan como dispositivos electro-quimio-mecánicos. Esto supone que al estar controlado su movimiento de flexión por una reacción electroquímica, cualquier magnitud fisica o química que afecte al equilibrio químico, modificará su comportamiento a través de la energía eléctrica consumida durante la actuación, como por ej emplo la corriente aplicada o la temperatura. Esta característica convierte a estos dispositivos en sensores de las condiciones ambientales y actuadores simultáneamente.Centro Universitario de la Defensa. Escuela de Turismo de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT. Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos y Minas (EICM). Escuela de Arquitectura e Ingeniería de Edificación (ARQ&IDE). Parque Tecnológico de Fuente Álamo. Navantia. Campus Mare Nostru