Understanding PEDOT doped with tosylate

Synchronous Cation-Driven and Anion-Driven Polypyrrole-Based Yarns toward In-Air Linear Actuators

Conducting polymers (CP) have shown great features in building textile actuators. To date, most of the yarn-based or CP-yarn actuators have been operated in liquid electrolytes in a three-electrode-cell configuration, comprising an external counter and a reference electrode. For integration in textiles, a two-electrode system is needed, where both electrodes are in a yarn format. This can be achieved by having two CP-yarns, where one acts as the anode and the other as the cathode. For these two CP-yarns to operate synchronically, they both need to expand (or contract) during opposite reactions. This can be achieved by doping one CP-yarn with mobile anions that will expand during oxidation, while the other CP-yarn should be doped with immobile anions expanding during reduction. As a result, the same movement is created upon opposite redox reactions, both collaborating with the actuation in the same direction without the need for an external passive electrode to close the electrical circuit, which could oppose or hinder the movement. Most of the studies on textile actuators are based on cation-driven CP-yarn actuators, while little is known about anion-driven systems in CP-yarn actuators. Here, we first present a study of the effect of the dopants, solvents, and polymer layer combinations on the mechanism and strain of CP-yarns. The CP-yarns are coated with two layers: an inner poly(3,4-ethylenedioxythiophene) (PEDOT) layer and the outer and active polypyrrole (PPy) layer. According to our results, the dopant of the inner PEDOT layer seems to affect the actuation mechanism of the outer PPy layer and, thereby, of the whole CP-yarn actuator, influencing the direction of the movement and enhancing or hindering the total strain of the actuator. We show that a CP-yarn coated with PEDOT(Tos)/PPy(ClO4) and actuated in LiClO4 aqueous solution showed a pure anion-driven actuation. Next, based on the latter results, we demonstrate for the first time the dual actuation of two CP-yarns, doped with two different dopants, ClO4 - and DBS-, actuating simultaneously driven by opposite redox reactions and exhibiting an average of 0.5% of strain, an important step toward in-air actuating yarns.

Organic Mixed Ionic-Electronic Conductors for Bioelectronic Sensors: Materials and Operation Mechanisms

The field of organic mixed ionic-electronic conductors (OMIECs) has gained significant attention due to their ability to transport both electrons and ions, making them promising candidates for various applications. Initially focused on inorganic materials, the exploration of mixed conduction has expanded to organic materials, especially polymers, owing to their advantages such as solution processability, flexibility, and property tunability. OMIECs, particularly in the form of polymers, possess both electronic and ionic transport functionalities. This review provides an overview of OMIECs in various aspects covering mechanisms of charge transport including electronic transport, ionic transport, and ionic-electronic coupling, as well as conducting/semiconducting conjugated polymers and their applications in organic bioelectronics, including (multi)sensors, neuromorphic devices, and electrochromic devices. OMIECs show promise in organic bioelectronics due to their compatibility with biological systems and the ability to modulate electronic conduction and ionic transport, resembling the principles of biological systems. Organic electrochemical transistors (OECTs) based on OMIECs offer significant potential for bioelectronic applications, responding to external stimuli through modulation of ionic transport. An in-depth review of recent research achievements in organic bioelectronic applications using OMIECs, categorized based on physical and chemical stimuli as well as neuromorphic devices and circuit applications, is presented.

PEDOT:PSS versus Polyaniline: A Comparative Study of Conducting Polymers for Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) based on conducting polymers have attracted significant attention in the field of biosensors. PEDOT:PSS and polyaniline (PANI) are representative conducting polymers used for OECTs. While there are many studies on PEDOT:PSS, there are not so many reports on PANI-based OECTs, and a detailed study to compare these two polymers has been desired. In this study, we investigated the fabrication conditions to produce the best performance in the OECTs using the above-mentioned two types of conducting polymers. The two main parameters were film thickness and film surface roughness. For PEDOT:PSS, the optimal conditions for fabricating thin films were a spin-coating rate of 3000 rpm and a DI water immersion time of 18 h. For PANI, the optimal conditions were a spin-coating rate of 3000 rpm and DI water immersion time of 5 s, and adding dodecylbenzenesulfonic acid (DBSA) was found to provide better OECT performances. The OECT performances based on PEDOT:PSS were superior to those based on PANI in terms of conductivity and transconductance, but PANI showed excellence in terms of film thickness and surface smoothness, leading to the good reproducibility of OECT performances.

Cell Viability Assessment of PEDOT Conducting Polymer-Coated Microneedles for Skin Sampling

Recently, transdermal monitoring and drug delivery have gained much interest, owing to the introduction of the minimally invasive microneedle (MN) device. The advancement of electroactive MNs electrically assisted in the capture of biomarkers or the triggering of drug release. Recent works have combined conducting polymers (CPs) onto MNs owing to the soft nature of the polymers and their tunable ionic and electronic conductivity. Though CPs are reported to work safely in the body, their biocompatibility in the skin has been insufficiently investigated. Furthermore, during electrical biasing of CPs, they undergo reduction or oxidation, which in practical terms leads to release/exchange of ions, which could pose biological risks. This work investigates the viability and proliferation of skin cells upon exposure to an electrochemically biased MN pair comprising two differently doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) polymers that have been designed for skin sampling use. The impact of biasing on human keratinocytes and dermal fibroblasts was determined at different initial cell seeding densities and incubation periods. Indirect testing was employed, whereby the culture media was first exposed to PEDOTs prior to the addition of this extract to cells. In all conditions, both unbiased and biased PEDOT extracts showed no cytotoxicity, but the viability and proliferation of cells cultured at a low cell seeding density were lower than those of the control after 48 h of incubation.

Real-Time Nitrate Ion Monitoring with Poly(3,4-ethylenedioxythiophene) (PEDOT) Materials

Nitrate (NO3) pollution in groundwater, caused by various factors both natural and synthetic, contributes to the decline of human health and well-being. Current techniques used for nitrate detection include spectroscopic, electrochemical, chromatography, and capillary electrophoresis. It is highly desired to develop a simple cost-effective alternative to these complex methods for nitrate detection. Therefore, a real-time poly (3,4-ethylenedioxythiophene) (PEDOT)-based sensor for nitrate ion detection via electrical property change is introduced in this study. Vapor phase polymerization (VPP) is used to create a polymer thin film. Variations in specific parameters during the process are tested and compared to develop new insights into PEDOT sensitivity towards nitrate ions. Through this study, the optimal fabrication parameters that produce a sensor with the highest sensitivity toward nitrate ions are determined. With the optimized parameters, the electrical resistance response of the sensor to 1000 ppm nitrate solution is 41.79%. Furthermore, the sensors can detect nitrate ranging from 1 ppm to 1000 ppm. The proposed sensor demonstrates excellent potential to detect the overabundance of nitrate ions in aqueous solutions in real time.

Ordered and disordered microstructures of nanoconfined conducting polymers

We probe the microstructural differences of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives under geometrical nanoconfinement using a high-resolution electron microscopy (HRTEM) technique. Highly ordered domains of poly(3,4-ethylenedioxythiophene):tosylate PEDOT:Tos, which is polymerized within alumina nanochannels, are observed. These features are in contrast to those of the polymer blend poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) PEDOT:PSS inserted into the nanopores. The extent of the order-disorder parameter in terms of surface crystallization and the number of ordered domains of the long-chain polymers strongly depends on the dopant environment, processing conditions and structural confinement. Atomic force spectroscopy of individual PEDOT nanochannels highlights counterion-dependent surface adhesive factors. The molecular dynamics (MD) simulation of these systems reveals similar polymer chain configurations and the resulting morphology.

Direct ink writing of PEDOT eutectogels as substrate-free dry electrodes for electromyography

Deep Eutectic Solvents (DES) are a new class of ionic conductive compounds attracting significant attention as greener alternatives to costly ionic liquids. Herein, we developed novel mixed ionic-electronic conducting materials by simple mixing of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) and various DES as additives. The DES addition induces the supramolecular assembly and gelification of PEDOT:PSS forming eutectogels triggered by extensive hydrogen bonding and charge stabilization. The eutectogels feature boosts the mixed ionic-electronic conductivity of PEDOT:PSS up to 368 S cm^-1, unveiling great potential as flexible bioelectronics. All the PEDOT:PSS/DES gels showed shear-thinning behavior and viscosity values ranging from 100 to 1000 Pa s. The eutectogels show good injectability with almost instantaneous elastic recovery, making them ideal materials for direct ink writing (DIW). As proof of that, PEDOT:PSS/DES (choline chloride:lactic acid) was 3D printed in different patterns, annealed at high temperature, and assembled into adhesive electrodes. This way tattoos-like electrodes, denoted as Eutecta2 were fabricated and placed in vivo on the forearm and the thumb of human volunteers for electromyography measurements. Eutecta2 hexagonal patterns showed excellent conformability, and their signal-to-noise ratio (SNR) was higher than Ag/AgCl commercial electrodes for thumb motion measurements. Furthermore, forearm motion was measured after 14 days with similar values of SNR, demonstrating long-term stability and reusability. All in all, our findings revealed that DES could be used as inexpensive and safe additives to direct the self-assembly of PEDOT:PSS into supramolecular eutectogels inks for flexible bioelectronics.

Nanostructured Poly(3,4-ethylenedioxythiophene) Coatings on Functionalized Glass for Energy Storage

Conducting polymers rise among some of the most promising transparent supercapacitor electrode materials due to high conductivity, environmental stability, light weight, and ease of synthesis. A major challenge for depositing conducting polymers on a glass substrate is the lack of molecular interactions between organic and inorganic moieties resulting in poor adhesion and low cycling stability of the electrode. We present a synthetic approach by covalently linking poly(3,4-ethylyenedioxythiophene) (PEDOT) and glass through Friedel-Crafts alkylation on a self-assembled diphenyldimethoxysilane monolayer. This method obviates the need for a conductive FTO or ITO coating, enabling the fabrication of current collector-free planar supercapacitor electrodes on any glass surface. The electrode produced from our vapor-phase synthesis is coated with a highly conductive nanofibrillar PEDOT film (sheet resistance 2.1 Ω/□) possessing a gravimetric capacitance of ∼200 F/g. Our PEDOT planar supercapacitor possesses outstanding stability (86% capacitance retention after 50,000 cycles). We also fabricate a proof-of-concept transparent tandem supercapacitor on PEDOT-coated glass using 3D-printed frames that supplies enough voltage and current to light up a blue light-emitting diode (LED).