Capacidad sensora de las reacciones electroquímicas del polipirrol : hacia el origen de la propiocepción natural y artificial.

Abstract

[SPA] En humanos y animales los músculos sienten, mientras actúan, las condiciones mecánicas, térmicas o químicas de trabajo: son músculos hápticos. Algunos investigadores vienen sospechando que es la propia reacción química impulsora de la actuación el origen de las señales sensoras enviadas de vuelta al cerebro. Para tratar de verificarlo en esta tesis se emplean películas de polipirrol como material modelo de la matriz intracelular en el sarcómero (máquinas moleculares, iones y agua). Al ser oxidadas y reducidas intercambian iones y agua con el electrolito transformándose en un gel denso y reactivo en los que cada cadena polimérica es una máquina molecular electroquímica. Se estudia con distintas técnicas electroquímicas (voltamperometría cíclica, ondas cuadradas de potencial o de corriente) cómo responden esas reacciones al cambiar la temperatura de trabajo, la concentración del electrolito o la frecuencia de la señal impulsora. Tanto la carga consumida, como la energía consumida o la evolución del potencial del material durante cada reacción cambian con las condiciones de reacción. Partiendo de la ecuación de la velocidad de reacción se obtienen las ecuaciones sensoras: relacionan cada magnitud sensora con cada una de las variables experimentales. Los resultados experimentales siguen las ecuaciones descritas. Se corrobora con ello el nuevo principio sensor: los sistemas reactivos (constituidos por máquinas moleculares químicas o electroquímicas) sujetos a perturbaciones energéticas ambientales responden adaptando su energía de reacción, o cualquiera de sus componentes, a las nuevas condiciones energéticas impuestas. Los resultados experimentales y el desarrollo teórico identifican a los potenciales químico y electroquímico durante la reacción (que definen las condiciones energéticas de la reacción) como origen de las señales sensoras en los músculos artificiales y, posiblemente, de la señal detectada por las terminaciones nerviosas en los músculos naturales y enviada al cerebro para informarle de las condiciones térmicas, químicas, eléctricas o mecánicas de trabajo. [ENG] Human and animal natural muscles feel the mechanical, thermal or chemical working conditions during actuation: they are haptic muscles. Some researchers suspect that the chemical reaction itself that drives the actuation is the origin of the sensing signals sent back to brain. In order to verify this issue, in this thesis polypyrrole films are used as model material of the intracellular matrix in the sarcomere (molecular machines, ions and water). At the oxidation and the reduction, they exchange ions and water with the electrolyte solution, becoming a dense and reactive gel where every polymeric chain is an electrochemical molecular machine. By the use of different electrochemical techniques (cyclic voltammetry, square potential waves and square current waves), the response of these reactions to changes in temperature, electrolyte concentration or frequency of imput signal are studied. Both, the charge and energy consumed and the evolution of the potential change with the working conditions during the reaction. Starting from the reaction rate equation, new sensing equations are obtained: they quantify the relationship between every sensing magnitude with every experimental variable. Experimental results fit the sensing equations developed. It corroborates the new sensing principle: reacting systems (constituted by chemical or electrochemical molecular machines) submitted to energetic perturbations respond to them by varying the reaction energy, or any of its components, to the new imposed energetic conditions. Both the experimental results and the theoretical development identify the chemical and the electrochemical potential during the reaction (that define the energetic conditions of the reaction) are the origin of the sensing signals in artificial muscles and, probably, of the signals detected by the neurotransmitters in natural muscles and sent back to the brain containing information about thermal, chemical, electric or mechanical working conditions.

[ENG] Human and animal natural muscles feel the mechanical, thermal or chemical working conditions during actuation: they are haptic muscles. Some researchers suspect that the chemical reaction itself that drives the actuation is the origin of the sensing signals sent back to brain. In order to verify this issue, in this thesis polypyrrole films are used as model material of the intracellular matrix in the sarcomere (molecular machines, ions and water). At the oxidation and the reduction, they exchange ions and water with the electrolyte solution, becoming a dense and reactive gel where every polymeric chain is an electrochemical molecular machine. By the use of different electrochemical techniques (cyclic voltammetry, square potential waves and square current waves), the response of these reactions to changes in temperature, electrolyte concentration or frequency of imput signal are studied. Both, the charge and energy consumed and the evolution of the potential change with the working conditions during the reaction. Starting from the reaction rate equation, new sensing equations are obtained: they quantify the relationship between every sensing magnitude with every experimental variable. Experimental results fit the sensing equations developed. It corroborates the new sensing principle: reacting systems (constituted by chemical or electrochemical molecular machines) submitted to energetic perturbations respond to them by varying the reaction energy, or any of its components, to the new imposed energetic conditions. Both the experimental results and the theoretical development identify the chemical and the electrochemical potential during the reaction (that define the energetic conditions of the reaction) are the origin of the sensing signals in artificial muscles and, probably, of the signals detected by the neurotransmitters in natural muscles and sent back to the brain containing information about thermal, chemical, electric or mechanical working conditions.