Chemical sensors from the cooperative actuation of multistep electrochemical molecular machines of polypyrrole: potentiostatic study. Trying to replicate muscle’s fatigue signals

Abstract

Polypyrrole film electrodes are constituted by multielectronic electrochemical molecular machines (every polymeric molecule) counterions and water, mimicking the intracellular matrix of muscular cells. The influence of the electrolyte concentration on the reversible oxidation/reduction of polypyrrole films was studied in NaCl aqueous solutions by consecutive square potential waves. The consumed redox charge and the consumed electrical energy change as a function of the concentration. That means that the extension (the consumed charge) of the reaction involving conformational, or allosteric, movements of the reacting polymeric chains (molecular machines) responds to (senses) the chemical energy of the reaction ambient. A theoretical description of the attained empirical results is presented getting the sensing equations and the concomitant sensitivities. Those results could indicate the origin and nature of the neural signals sent to the brain from biological haptic muscles working by cooperative actuation of the actin-myosin molecular machines driven by chemical reactions and sensing, simultaneously, the fatigue state of the muscle.

Bioinspired polypyrrole based fibrillary artificial muscle with actuation and intrinsic sensing capabilities

“…reversible oxidation and reduction of polymeric chains 30 , 31 . The electrochemical reactions of the polymer induce the conformational movement of the chains, the microscopic cooperative actuation leading to the macroscopic swelling and shrinking of the polymer structure during oxidation and reduction by the subsequent lodging and expelling of electrolyte molecules, respectively 32 , 33 . Since the actuation properties are a consequence of the microscopic movements of swelling and shrinking of every single monomer chain, independently of the structure, the cooperative actuation creates a macroscopic movement, which will depend on the isotropy of the material.…”

Exploring Brain Information Storage/Reading for Neuronal Connectivity Using Macromolecular Electrochemical Sensing Motors

“…The theoretical sensing equations describing the responses to potential or current driving cycles were also attained from the basic equation of the driving reaction rate. [ 78,135 ]…”

“…Summarizing, the electrochemical actuation of any macromolecular motor reads both the permanent energetic conformational memory stored by its conformational compacted structure (long‐term memory)and the local physical and chemical energetic conditions (short‐term memory). These packages of quantitative information—the stored permanent conformational energy and the local mechanical, [ 128 ] chemical, [ 133,135 ] thermal, [ 78,126,134,143,144 ] and electrical [ 145,146 ] energetic conditions—are carried simultaneously by the energy of the generated ionic pulse (Equation () and ()).…”

The Energy Consumed by Electrochemical Molecular Machines as Self‐Sensor of the Reaction Conditions: Origin of Sensing Nervous Pulses and Asymmetry in Biological Functions

“… Evolution of the specific reaction energy consumed during the oxidation (anodic) or reduction (cathodic) of a pPy film submitted to: a) consecutive potential sweeps between −0.35 and 0.25 V at a scan rate of 90 mV s −1 . b) potential square waves of ±0.1 V for 6 s each (reproduced with permission . Copyright 2018, IOP Science), and c) current square waves at ±1 mA for 6 s each, at different NaCl aqueous solution concentrations at room temperature.…”

“…Using basic electrochemical, polymeric and mechanical principles a theoretical description of sensing and tactile artificial muscles (artificial proprioception) has been attained ,,,,. The way is open for a theoretical (physical‐chemical) description of bioreplicating chemical‐driven properties and functions.…”