The cooperative actuation of polypyrrole electrochemical machines senses the chemical conditions as muscles sense their fatigue state

Polypyrrole films are constituted by multistep electrochemical molecular machines, counterions and water, and have been considered here as a material model of the intracellular matrix in muscular cells. Their reversible oxidation/reduction in different concentrations of NaCl aqueous solution was studied by consecutive square current waves. The evolution of both, the material potential and the consumed electrical energy during every reaction, changes as a function of the electrolyte concentration. The reactions involving molecular motors as reactants respond to (and sense) any chemical energetic perturbations of the reaction ambient (variations of electrolyte concentration here), by adapting the evolution of the material potential and that of the consumed reaction energy to fit the new energetic conditions. A theoretical description of the attained empirical results is presented getting the sensing equations and the concomitant sensitivities. The results could indicate how the neuronal signal informing the brain about the fatigue state of a muscle is generated from the muscular chemical potential or the consumed reaction energy at any time. The actin-myosin-ATP reaction should originate, simultaneously, actuating and sensing biological functions.