Electrochemical stability of PEDOT for wearable on‐skin application

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.

Electroactive and Stretchable Hydrogels of 3,4-Ethylenedioxythiophene/thiophene Copolymers

Hydrogels are conductive and stretchable, allowing for their use in flexible electronic devices, such as electronic skins, sensors, human motion monitoring, brain-computer interface, and so on. Herein, we synthesized the copolymers having various molar ratios of 3,4-ethylenedioxythiophene (EDOT) to thiophene (Th), which served as conductive additives. With doping engineering and incorporation with P(EDOT-co-Th) copolymers, hydrogels have presented excellent physical/chemical/electrical properties. It was found that the mechanical strength, adhesion ability, and conductivity of hydrogels were highly dependent on the molar ratio of EDOT to Th of the copolymers. The more the EDOT, the stronger the tensile strength and the greater the conductivity, but the lower the elongation break tends to be. By comprehensively evaluating the physical/chemical/electrical properties and cost of material use, the hydrogel incorporated with a 7:3 molar ratio P(EDOT-co-Th) copolymer was an optimal formulation for soft electronic devices.

Recent advances in the aqueous applications of PEDOT

Water is ubiquitous in life - from making up the majority of the Earth's surface (by area) to over half of the human body (by weight). It stands to reason that materials are likely to contact water at some point during their lifetime. In the specific case of sensors however, there is a need to consider materials that display stable function while immersed in aqueous applications. This mini-review will discuss the most recent advances (2018 to 2021) in the application of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) in aqueous environments. At its heart, the use of PEDOT in aqueous applications relies on nanoscale understanding and/or nanoengineered structures and properties. This enables their use in water-based settings such as within the human body or buried in agricultural soils.

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry

Electrochemical impedance spectroscopy (EIS) is a highly applicable electrochemical, analytical, and non-invasive technique for materials characterization, which allows the user to evaluate the impact, efficiency, and magnitude of different components within an electrical circuit at a higher resolution than other common electrochemical techniques such as cyclic voltammetry (CV) or chronoamperometry. EIS can be used to study mechanisms of surface reactions, evaluate kinetics and mass transport, and study the level of corrosion on conductive materials, just to name a few. Therefore, this review demonstrates the scope of physical properties of the materials that can be studied using EIS, such as for characterization of supercapacitors, dye-sensitized solar cells (DSSCs), conductive coatings, sensors, self-assembled monolayers (SAMs), and other materials. This guide was created to support beginner and intermediate level researchers in EIS studies to inspire a wider application of this technique for materials characterization. In this work, we provide a summary of the essential background theory of EIS, including experimental design, signal responses, and instrumentation. Then, we discuss the main graphical representations for EIS data, including a scope of the foundation principles of Nyquist, Bode phase angle, Bode magnitude, capacitance and Randles plots, followed by detailed step-by-step explanations of the corresponding calculations that evolve from these graphs and direct examples from the literature highlighting practical applications of EIS for characterization of different types of materials. In addition, we discuss various applications of EIS technique for materials research.

This manuscript highlights a beginner-to-intermediate level scope of electrochemical impedance spectroscopy (EIS), which is an indispensable, non-destructive electrochemical technique that can be applied for materials characterization.