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Organic mixed ionic‐electronic conductors (OMIEC) have emerged as pivotal materials in organic bioelectronics, particularly when integrated into organic electrochemical transistors (OECTs). Conducting polymer‐based devices have indeed demonstrated their capability to transduce biological signals into amplified output signals, harnessing the high transconductance of OECTs. The OECT operating principle and sensing capability strongly depend on ion‐conjugated backbone coupling: the dual nature of OMIECs, i.e. ion‐conductor and electron/hole‐conductor, presents an intrinsic interface in the bulk of the thin film across which transduction of ionic signals into electronic signals and vice versa occurs. Recent works have shown how selective sodium and potassium detection can be achieved by direct chemical modification of the polymer. Such modifications introduce ligands with affinity for the cations of interest as substituents on the polymer chain. The present work explores the integration of specifically modified conducting polymers into OECT channels, offering selectivity for zinc cations. Zinc fluxes are crucial in various biological processes, and their reliable detection, especially at low concentrations, is an important challenge. By electropolymerizing a thiophene‐based trimer, modified with a dipicolylamine (DPA) substituent, a conducting polymer‐based OECT is obtained that can selectively detect Zn2+ in the 10−6 to 10−3 mol L−1 concentration range in physiological buffers. [ABSTRACT FROM AUTHOR]

Conducting polymers find applications as active materials in electrochromic devices thanks to their tunable optoelectronic and electrochemical properties. Such versatility can be further enhanced by copolymerizing various aromatic monomers in order to produce new materials. In this work, we present different copolymers obtained by electropolymerization of an N‐substituted dithienylpyrrole (SNSBA) with either 3,4‐ethylendioxythiophene (EDOT) or bithiophene (BTh). The electrochemical, spectroscopic, and electrical properties were characterized across their different neutral and charged states by means of ex‐situ and in‐situ spectroelectrochemical techniques. The peculiar feature of SNSBA lies in the aniline bearing substituent of the central pyrrole unit that allows polymerization to occur at three different sites, yielding a cross‐linked polymer network. Our findings show that the SNSBA comonomer not only influences the optoelectronic properties of the final materials with respect to their homopolymers, but also induces a lowering of the hysteresis of the insulating/conducting transition (ΔEG<280 mV), likely due to the cross‐linked nature of the polymer layer. These features are promising to develop a new class of copolymers for electrochromic devices with stable, reversible, and fast operation. [ABSTRACT FROM AUTHOR]

Artificial actuators have been extensively studied due to their wide range of applications from soft robotics to biomedicine. Herein we introduce an autonomous bi-enzymatic system where reversible motion is triggered by the spontaneous oxidation and reduction of glucose and oxygen, respectively. This chemo-mechanical actuation is completely autonomous and does not require any external trigger to induce self-sustained motion. The device takes advantage of the asymmetric uptake and release of ions on the anisotropic surface of a conducting polymer strip, occurring during the operation of the enzymes glucose oxidase and bilirubin oxidase immobilized on its surface. Both enzymes are connected via a redox polymer at each extremity of the strip, but at the opposite faces of the polymer film. The time-asymmetric consumption of both fuels by the enzymatic reactions produces a double break of symmetry of the film, leading to autonomous actuation. An additional break of symmetry, introduced by the irreversible overoxidation of one extremity of the polymer film, leads to a crawling-type motion of the free-standing polymer film. These reactions occur in a virtually unlimited continuous loop, causing long-term autonomous actuation of the device. Owing to their interesting applications from soft robotics to biomedicine, methodologies to produce artificial actuators are desirable. Herein the authors develop an autonomous soft bioelectrochemical actuator with self-sustained motion triggered by spontaneous enzymatic reactions. [ABSTRACT FROM AUTHOR]

Conducting polymers have gained considerable attention for the possible design of localized electroactive patterns for microelectronics. In this work, the authors take advantage of the properties of polypyrrole, in synergy with a wireless polarization, triggered by bipolar electrochemistry, to produce localized resistance gradient patterns. The physicochemical modification is caused by the reduction and overoxidation of polypyrrole, which produces highly resistive regions at different positions along the conducting substrate at predefined locations. Due to the outstanding flexibility of polypyrrole, U‐, S‐, and E‐shaped bipolar electrodes can be formed for prove‐of‐concept experiments, and electrochemically modified in order to generate well‐defined resistance gradients. Energy‐dispersive X‐ray spectroscopy analysis of the samples confirms the localized physicochemical modifications. This approach presents as main advantages the wireless nature of bipolar electrochemistry and the possible fine‐tuning of the spatial distribution of the electrochemical modification, in comparison with more conventional patterning methods. [ABSTRACT FROM AUTHOR]

Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein, a wireless enantio‐responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever‐type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications. [ABSTRACT FROM AUTHOR]

Conducting polymers have been extensively studied due to their potential applications ranging from sensing to energy storage, and environmental remediation. They can be easily generated by electrosynthesis and have also very interesting electrochemical features, which have been mostly examined with classic electrochemical approaches. Bipolar electrochemistry offers an attractive alternative way to synthesize and characterize the physico‐chemical properties of conducting polymers. The wireless and asymmetric features of bipolar electrochemistry can be advantageously combined with the electroactivity, tunability and easy processability of conducting polymers. This synergy has been increasingly explored in recent years for the controlled electrogeneration, surface modification and characterization of different π‐conjugated polymers. This review summarizes the advances in this context and also discusses some unconventional applications such as wireless light‐emitting devices and actuators. [ABSTRACT FROM AUTHOR]

Bipolar electrochemistry has gained increasing attention in recent years as an attractive transduction concept in analytical chemistry in general and, more specifically, in the frame of chiral recognition. Herein, we use this concept of wireless electrochemistry, based on the combination of the enantioselective oxidation of a chiral probe with the emission of light from a light‐emitting diode (LED), as an alternative for an easy and straightforward readout of the presence of chiral molecules in solution. A hybrid polymer‐microelectronic device was designed, using an inherently chiral oligomer, that is, oligo‐(3,3′‐dibenzothiophene) and a polypyrrole strip as the anode and cathode of a miniaturized LED. The wireless induced redox reactions trigger light emission when the probe with the right chirality is present in solution, whereas no light emission is observed for the opposite enantiomer. The average light intensity shows a linear correlation with the analyte concentration, and the concept opens the possibility to quantify the enantiomeric excess in mixtures of the molecular antipodes. [ABSTRACT FROM AUTHOR]

Actuators controlled by external stimuli have received a lot of attention in recent years. Herein a polymer based dual stimuli actuator is reported, triggered by light and an electric field. This allows better control of actuation, enlarging the field of potential applications, like, for example, in the frame of soft robotics. The actuator is composed of polypyrrole and TiO2 modified with methylene blue. In an aqueous solution, the resulting freestanding hybrid film shows reversible actuation due to the synergy of light and an applied electric field. Illumination with light produces electron‐hole pairs in the TiO2 layer, which are shuttled to the opposite ends of the actuator by the potential gradient present in the solution. This results in electrochemical oxidation and reduction reactions at the two extremities and consequently in site selective swelling of the polymer, which finally leads to a controlled motion of the actuator, following the principles of logic gate operations. Such synergistically induced switching allows developing original actuation schemes for performing complex mechanical tasks triggered by more than one stimulus. [ABSTRACT FROM AUTHOR]

An approach providing cation‐selective poly‐(3,4‐ethylenedioxythiophene)(PEDOT):polyelectrolyte‐mixed conductors is presented in this communication based on the structural modification of this ambivalent (ionic and electronic conductive) polymer complex. First, an 18‐crown‐6 moiety is integrated into the styrene sulfonate monomer structure as a specific metal cation scavenger particularly targeting K+ versus Na+ detection. This newly functionalized monomer is characterized by 1H NMR titration to evaluate the ion selectivity. Aqueous PEDOT dispersion inks containing the polymeric ion‐selective moieties are designed and their electrical and electrochemical properties analyzed. These biocompatible inks are the first proof‐of‐concept step towards ion selectivity in view of their interfacing with biological cells and microorgans of interest in the field of biosensors and physiology. [ABSTRACT FROM AUTHOR]

Bipolar electrochemistry can be used in different ways to induce motion of an object, for example by generating gas bubbles in an asymmetric way or by a wireless self-regeneration mechanism due to the intrinsic symmetry breaking of this concept. Here a complementary approach is explored on the basis of conducting polymer objects addressed in solution by an electric field. The presence of the latter results in a differential polarization of the polymer, thus enabling its oxidation at one extremity and its reduction at the opposite side. This triggers different degrees of swelling and shrinking, leading to important deformations of the object. Combined with an additional asymmetry in the polymer surface morphology, a periodic switching of the electric field orientation allows exploiting these deformations to induce directed crawling motion. This first example of a wireless biomimetic crawler based on conducting polymers opens interesting long-term perspectives in several areas such as for example wireless valves, pumps and (micro)robotics. [ABSTRACT FROM AUTHOR]

Electrochemical actuation of conducting polymers usually requires a direct connection to an electric power supply. In this contribution, we suggest to overcome this issue by using the concept of bipolar electrochemistry. This allows changing the oxidation state of the polymer in a gradual and wireless way. Free-standing polypyrrole films were synthesized with an intrinsic morphological asymmetry of their two faces in order to form a bilayer structure. Immersing such objects in an electrolyte solution and exposing them to a potential gradient leads to the asymmetric oxidation/reduction of the polymer, resulting in differential shrinking and swelling along the main axis. This additional asymmetry is responsible for a structural deformation. Optimization allowed highly efficient bending, which is expected to open up completely new directions in the field of actuation due to the wireless mode of action. [ABSTRACT FROM AUTHOR]

Actuation, Bipolar electrochemistry, Conducting polymers, Electro-organic synthesis, Light emitting systems Keywords: Actuation; Bipolar electrochemistry; Conducting polymers; Electro-organic synthesis; Light emitting systems EN Actuation Bipolar electrochemistry Conducting polymers Electro-organic synthesis Light emitting systems 1 1 1 02/01/22 20220114 NES 220114 B The Cover Feature b illustrates different experiments performed with conducting polymers and using the concept of bipolar electrochemistry. [Extracted from the article]

Abstract: Microelectrode arrays (MEAs) are widely used tools for recording and stimulating extracellular neuronal activity. Major limitations when decreasing electrode size in dense arrays are increased noise level and low charge injection capability. Nanostructuration of the electrode sites on MEAs presents an efficient way to overcome these problems by decreasing the impedance of the electrode/solution interface. Here, we review different techniques used to achieve this goal including template assisted electrodeposition for generating macro- and mesoporous films, immobilization of carbon nanotubes (CNTs) and deposition of conducting polymers onto microelectrodes. When tested during in vitro and in vivo measurements, nanostructured MEAs display improved sensitivity during recording of neuronal activity together with a higher efficiency in the stimulation process compared to conventional microelectrodes. [Copyright &y& Elsevier]

Electrochemical water-splitting is one of the key reactions that lay the basis for the storage of energy produced by sustainable sources. The development of fast methods to evaluate the electrocatalytic activity of electrode materials with respect to the oxidation and reduction of water are therefore required to make further progress in this exciting field of research. Here, we present a novel method based on bipolar electrochemistry, which allows evaluating the electrocatalytic activity of a material towards hydrogen and oxygen evolution (HER and OER, respectively) with a single device. This method is based on the capability of a conducting polymer layer to behave as a variable-resistance switch as a function of its electrochemical doping. This approach was used to evaluate the electrocatalytic activity of Au, Pt and Ni surfaces towards HER and OER in terms of the half-wave electric field, ε1/2, obtained during the insulating/conducting transition of poly-3,4-ortho-xylen-dioxythiophene (PXDOT). The trends of ε 1/2 variations are in agreement with data reported with classical electrochemical methods. In this work, we developed an easy and straightforward method to evaluate the electrocatalytic activity of electrode materials for water-splitting. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo12O40 3−), to form stable anionic monolayers on carbon nanoparticles and multi-wall nanotubes is explored here to produce stable colloidal solutions of polyoxometallate covered carbon nanostructures and to disperse them within conducting polymer, poly(3,4-ethylenedioxythiophene), i.e. PEDOT, or polyaniline multilayer films. By repeated alternate treatments in the colloidal suspension of PMo12O40 3−-protected carbon nanoparticles or nanotubes, and in the acid solution of a monomer (3,4-ethylenedioxythiophene or aniline), the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional organized arrangements (networks) of interconnected organic and inorganic layers on electrode (e.g. glassy carbon) surfaces. In hybrid films, the negatively charged polyoxometallate-covered carbon nanostructures interact electrostatically with positively charged conducting polymer ultra-thin layers. Consequently, the attractive electrochemical charging properties of conducting polymers, reversible redox behavior of polyoxometallate, as well as the mechanical and electrical properties of carbon nanoparticles or nanotubes can be combined. The films are characterized by fast dynamics of charge transport, and they are of potential importance to electrocatalysis and charge storage in redox capacitors. [Copyright &y& Elsevier]