Highly Electrically Conductive Flexible Ionogels by Drop-Casting Ionic Liquid/PEDOT:PSS Composite Liquids onto Hydrogel Networks

Cellulose nanocomposite hydrogel-conductive, antimicrobial and high tenacity sensor for information encryption, human motion monitoring and animal behavior studies

Conductive hydrogels have garnered significant attention in advanced applications, particularly in wearable strain sensors. Nevertheless, the challenge of fabricating wearable sensors that demonstrate both optimal mechanical properties and high conductivity persists. In this study, we successfully developed a multifunctional hydrogel sensor comprising acrylamide (AM), polyethylene glycol (PEG), and sodium carboxymethyl cellulose (CMC). The resulting hydrogel demonstrated favorable mechanical properties, electrical conductivity, adhesion, antimicrobial activity, antifreezing capability, moisture retention, fluorescence, and strain sensitivity. Notably, the sensor retains its flexibility and electrical conductivity even at -20 °C. The incorporation of doped carbon quantum dots imparts pronounced fluorescence properties to the hydrogel, facilitating clear topographical imaging and paving the way for potential applications in information encryption. The fabricated strain sensors exhibit broad applicability and high reliability in human motion monitoring, allowing for secure attachment to the human body without the need for additional adhesives. Both large movements, such as joint bending (e.g., wrists and knees), and subtle movements, such as chewing and swallowing, can be accurately monitored. Furthermore, this study aims to integrate flexible hydrogel sensor technology with pet behavior monitoring, with the objective of identifying the emotional states of dogs. The ultimate goal is to establish a novel model for animal behavior research.

Filler-free cellulose nanofiber composite papers with excellent mechanical properties for efficient electromagnetic interference shielding

The vast majority of conductive polymer composites (CPCs) currently available for electromagnetic interference (EMI) shielding rely on inorganic conductive fillers to construct conductive networks. However, the strategy inevitably causes some compromises in the biocompatibility, biodegradability, and mechanical properties of CPCs. In this work, the filler-free and high conductive cellulose nanofiber (CNF) composite papers containing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped by lithium bis(trifloromethanesulfonyl) imide (Li-TFSI) are reported. The resultant Li-TFSI@PEDOT:PSS/CNF (LPPC) composite papers exhibit an exceptional absolute EMI shielding effectiveness of 14,525.5 dB∙cm-1, surpassing the reported values of many CPCs-based EMI shielding materials containing inorganic fillers. Li-TFSI can induce the structural reorganization of PEDOT chains. The conductivity of Li-TFSI@PEDOT:PSS was boosted with the enhancement of the crystalline order and oxidation level of PEDOT chains. Furthermore, the obtained LPPC composite papers demonstrate outstanding mechanical properties with a tensile strength of 44.42 MPa and EMI shielding stability with a retention ratio of up to 97 %, which are desirable for EMI shielding in wearable devices. Therefore, this work provides a feasible strategy to construct filler-free CPCs-based EMI shielding materials, which are expected to provide electromagnetic protection for the next flexible devices.

Poly(3, 4-Ethylenedioxythiophene) as Promising Energy Storage Materials in Zinc-Ion Batteries

Benefiting from the advantages of high conductivity and good electrochemical stability, the conjugated conducting polymer poly (3, 4-ethylenedioxythiophene) is a promising energy storage material in zinc-ion batteries. Zinc-ion batteries have the advantages of high safety, environmental friendliness, and low cost, but suffer from unstable cathode material structure, poor electrical conductivity, and uncontrollable dendritic growth of zinc anodes. PEDOT, with its fast electrochemical response and wide potential window, is expected to make up for the shortcomings and enhance capacity and cycle life of zinc-ion batteries. Herein, in this review different polymerization methods of poly (3, 4-ethylenedioxythiophene) as well as their structure and properties are summarized; the progress in doping strategies related to the increasing conductivity and dispersivity of poly (3, 4-ethylenedioxythiophene) materials is discussed; specific applications of poly (3, 4-ethylenedioxythiophene)-based materials in anode, cathode, electrolyte, and binder of zinc-ion batteries are explored; and the representative advancements for improving the electrochemical performance of poly (3, 4-ethylenedioxythiophene) in zinc-ion batteries are emphasized. Finally, the current challenges of poly (3, 4-ethylenedioxythiophene) as promising materials in zinc-ion batteries and an insight into their future research directions are pointed out.

Citric Acid and Polyvinyl Alcohol Induced PEDOT: PSS with Enhanced Electrical Conductivity and Stretchability for Eco-Friendly, Self-Healable, Wearable Organic Thermoelectrics

Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is a promising material for organic thermoelectric (TE) applications. However, it is challenging to achieve PEDOT: PSS composites with stretchable, self-healable, and high TE performance. Furthermore, some existing self-healing TE materials employ toxic reagents, posing risks to human health and the environment. In this study, a novel intrinsically self-healable and wearable composite is developed by incorporating environmentally friendly, highly biocompatible, and biodegradable materials of polyvinyl alcohol (PVA) and citric acid (CA) into PEDOT: PSS. This results in the formation of double hydrogen bonding networks among CA, PVA, and PEDOT: PSS, inducing microstructure alignment and leading to simultaneous enhancements in both TE performance and stretchability. The resulting composites exhibit a high electrical conductivity and power factor of 259.3 ± 11.7 S·cm-1, 6.9 ± 0.4 µW·m-1·K-2, along with a tensile strain up to 68%. Furthermore, the composites display impressive self-healing ability, with 84% recovery in electrical conductivity and an 85% recovery in tensile strain. Additionally, the temperature and strain sensors based on the PEDOT: PSS/PVA/CA are prepared, which exhibit high resolution suitable for human-machine interaction and wearable devices. This work provides a reliable and robust solution for the development of environmentally friendly, self-healing and wearable TE thermoelectrics.

Zwitterionic Eutectogels with High Ionic Conductivity for Environmentally Tolerant and Self-Healing Triboelectric Nanogenerators

Eutectogels have garnered considerable attention for the development of wearable devices, owing to their inherent mechanical elasticity, ionic conductivity, affordability, and environmental compatibility. However, the low conductivity of existing eutectogels has impeded their progression in electronic applications. Here, we report a zwitterionic eutectogel with an impressive ionic conductivity of up to 15.7 mS cm-1. The incorporation of zwitterionic groups into the eutectogel creates ample mobile charges by dissociating the cation and anion of solvents, thereby yielding exceptional ionic conductivity. Moreover, the abundant electrostatic and hydrogen bonding interactions within the eutectogel endow it with prominent self-healing and adhesive properties. By integrating the eutectogel with a roughly patterned polydimethylsiloxane film, we have successfully constructed a triboelectric nanogenerator (TENG) with a maximum output power density of 112 mW m-2. This TENG is capable of generating stable electrical signals even in extreme temperature conditions ranging from -80 to 100 °C and effectively powering electronic devices. Furthermore, the assembled TENG displays high sensitivity as a self-powered sensor, enabling real-time and precise monitoring of signals derived from human motions. This study establishes a promising approach for the development of sustainable and multifunctional flexible electronics that are resilient in extreme environments.

Manipulation of cross-linking in PEDOT:PSS hydrogels for biointerfacing

Conducting hydrogels can be used to fabricate bioelectronic devices that are soft for improved cell- and tissue-interfacing. Those based on conjugated polymers, such as poly(3,4-ethylene-dioxythiophene):polystyrene sulfonate (PEDOT:PSS), can be made simply with solution-based processing techniques, yet the influence of fabrication variables on final gel properties is not fully understood. In this study, we investigated if PEDOT:PSS cross-linking could be manipulated by changing the concentration of a gelling agent, ionic liquid, in the hydrogel precursor mixture. Rheology and gelation kinetics of precursor mixtures were investigated, and aqueous stability, swelling, conductivity, stiffness, and cytocompatibility of formed hydrogels were characterized. Increasing ionic liquid concentration was found to increase cross-linking as measured by decreased swelling, decreased non-network fraction, increased stiffness, and increased conductivity. Such manipulation of IL concentration thus afforded control of final gel properties and was utilized in further investigations of biointerfacing. When cross-linked sufficiently, PEDOT:PSS hydrogels were stable in sterile cell culture conditions for at least 28 days. Additionally, hydrogels supported a viable and proliferating population of human dermal fibroblasts for at least two weeks. Collectively, these characterizations of stability and cytocompatibility illustrate that these PEDOT:PSS hydrogels have significant promise for biointerfacing applications that require soft materials for direct interaction with cells.

MXene-enhanced ePatch with antibacterial activity for wound healing

Prudent wound-healing strategies hold great potential in expediting tissue renovation and regeneration. Despite the widespread adoption of hydrogels as preferred carriers for wound healing patches, achieving optimal mechanical compatibility and superior wound performance remains a formidable challenge. Consequently, meticulous attention must be given to the formulation of hydrogel structure and materials design to overcome these hurdles. In response, we have developed an ePatch composed of polyacrylamide (PAAM) as the primary hydrogel structure, augmented with MXene, silver nanowires (AgNWs), and resveratrol to act as sustained-release agents, structural enhancers, and antibacterial agents, respectively. Notably, the ePatch exhibited exceptional wound-fitting capabilities and impressive mechanical stretchability (with a relative standard deviation [RSD] of only 1.36% after 55 stretches) and Young's modulus. In contrast to the commercial 3M Tegaderm, the ePatch demonstrated superior wound healing properties, with the inclusion of MXene into PAAM/AgNWs playing a pivotal role in expanding the ePatch's potential use across various interconnected fields.

Sialic acid biosensing by post-printing modification of PEDOT:PSS with pyridylboronic acid

A poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based conducting polymer, which has biorecognition capabilities, has promising biosensing applications. Previously, we developed a facile method for post-printing chemical modification of PEDOT:PSS thin films from commercial sources. Molecular recognition elements were directly introduced into the PSS side chain by a two-step chemical reaction: introduction of an ethylenediamine linker via an acid chloride reaction of the sulfonate moiety, and subsequent receptor attachment to the linker via amine coupling. In this study, the same method was used to introduce 6-carboxypyridine-3-boronic acid (carboxy-PyBA) into the linker for specifically detecting N-acetylneuraminic acid (sialic acid, SA), as a cancer biomarker. The surface-modified PEDOT:PSS films were characterized by X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and static water contact angle and conductivity measurements. The specific interaction between PyBA and SA was detected by label-free reagent-free potentiometry. The SA-specific negative potential responses of modified PEDOT:PSS electrodes, which was ascribed to an SA carboxyl anion, were observed in a physiologically relevant SA range (1.6-2.9 mM) at pH 5, in a concentration-dependent manner even in the presence of 10% fetal bovine serum. The sensitivity was -2.9 mV/mM in 1-5 mM SA with a limit of detection of 0.7 mM. The sensing performances were almost equivalent to those of existing graphene-based electrical SA sensors. These results show that our chemical derivatization method for printing PEDOT:PSS thin films will have applications in SA clinical diagnostics.