Flexible Conductive Polymer Research Articles

Flexible conductive polymer composite film with sandwich-like structure for ultra-efficient and high-stability electromagnetic interference shielding

Flexible electromagnetic interference (EMI) shielding films with the merits of light-weight, flexibility, and high EMI shielding performance are the essential materials for the consumer electronics and communication products. Herein, we construct a hybrid conductive network based on the electrospinning thermoplastic polyurethane (TPU) film loaded with different dimensional conductive fillers, including 0D FeCl3, 1D carbon nanotube (CNT) and 2D graphene nanosheet (GN) to achieve a flexible, light-weight, and ultra-efficient EMI shielding composite film. In specific, the electrospinning porous TPU film is firstly anchored by CNTs assisted by ultrasound to generate the porous TPU/CNT film. Thereafter, the as-prepared porous TPU/CNT film is loaded a GN/CNT/FeCl3 layer by vacuum-assisted filtration to generate a double-layer GN/CNT/FeCl3@TPU/CNT film. Finally, another porous TPU/CNT film is sealed onto the GN/CNT/FeCl3@TPU/CNT film by hot-pressing, which fabricates a sandwiched TPU/CNT@GN/CNT/FeCl3@TPU/CNT composite film. It is interesting to note that the composite film possesses the ultrahigh EMI shielding value (56.0 dB at 10.0 GHz) in the X-band (8.2–12.4 GHz) with high flexibility, excellent mechanical properties, long-term durability (acid-base environment resistance and stability after 1000 bends), as well as high thermal conductivity (6.53 W/(m.K)). This work proposes a simple but efficiency strategy to design the flexible EMI shielding film with ultra-high performance and outstanding durability.

Synthesis of nanostructured zinc oxide and its composite with carbon dots for DSSCs applications using flexible electrode

ZnO nanowires (ZnO NWs), ZnO nanoparticles (ZnO NPs) and carbon dots (C-dots) were synthesized by hydrothermal, sol-gel and hydrothermal methods respectively. They were also characterized and applied for dye sensitized solar cells (DSSCs). The effects of C-dots on ZnO NWs and ZnO NPs have been evaluated. The C-dots were used at a mole ratio of citric acid (CA) to ethylene diamine (EDA) of 1 : 1.5. These C-dots were found to enhance the performance of the flexible electrode DSSCs. After the addition of C-dots, the power conversion efficiency (PCE) of ZnO NPs was boosted to be two times higher than that of ZnO NPs DSSCs without C-dots. Similarly, the ultraviolet (UV)-band revealed a blue shift, resulting in a lower band gap and a reduced charge transfer resistance, which can enhance the PCE of DSSCs. The loaded quantity on the flexible electrode substrate made of polyethylene terephthalate (PET) was optimized (50 mg). For DSSCs, the PET flexible electrode conductive polymer has produced positive outcomes. For ZnO NWs and ZnO NWs@C-dots, the PCE values were 1.45% and 4.25%; while for ZnO NPs and ZnO NPs@C-dots, they were 2.34% and 5.81%, respectively. This work achieved remarkable and competitive performance when compared to solid (indium tin oxides/glass)-based substrate.

Structure, principle and performance of flexible conductive polymer strain sensors: a review

Structure, principle and performance of flexible conductive polymer strain sensors: a review

Fabrication and evaluation of a flexible antenna device composed of a compatible iron-oxide clay in a PDMS graphene matrix

We create a flexible and robust conductive polymer composite based on iron oxide and a thin film of clay doped with graphene nanoparticles, and test its application as a wearable device for underground workers.

Ultrafast Laser‐Induced Excellent Thermoelectric Performance of PEDOT:PSS Films

Because poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) is water processable, thermally stable, and highly conductive, PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials. However, the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity, thus cannot be directly utilized for TE applications. Here, a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated. Under optimal conditions, the electrical conductivity of the treated film is increased to 803.1 S cm−1 from 1.2 S cm−1 around three order of magnitude higher, and the power factor is improved to 19.0 μW m−1 K−2, which is enhanced more than 200 times. The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation, reduction of the interplanar stacking distance, and the removal of insulating PSS with increasing the oxidation level of PEDOT, facilitating the charge transportation. This work presents an effective route for fabricating high‐performance flexible conductive polymer films and wearable thermoelectric devices.

Waste flame-retardant polyurethane foam/ground tire rubber/carbon nanotubes composites with hierarchical segregated structures for high efficiency electromagnetic interference shielding

Recently, flexible conductive polymer composites (CPCs) have attracted increasing interests for their promise in electromagnetic interference (EMI) shielding. Inspired by the “steel reinforced concrete” structure, we proposed in this study a novel method to prepare a CPC with high EMI shielding performance from waste flame-retardant polyurethane foam (WFPUF) and ground tire rubber (GTR). In this CPC, WFPUF coated with carbon nanotubes (CNT) and cellulose nanofibers (CNF) served as a strong and conductive skeleton like the “steel” in “steel reinforced concrete”. Meanwhile, the GTR and CNT composite with a segregated structure occupied the pore space of WFPUF/CNT/CNF (WCC) to form the WCC/GTR/CNT composite, similar to the “concrete” in “steel reinforced concrete”. Owing to such a hierarchical structure, the resultant WCC/GTR/CNT demonstrated some coveted properties, including the enhanced mechanical properties, high electrical conductivity (84.0 S·m−1), excellent EMI shielding performance (53.8 dB), and long-term durability. Remarkably, the composite also showed great flame retardancy due to the presence of WFPUF. This work provided a promising strategy for the preparation of eco-friendly, low cost, flexible and efficient CPCs from polymer wastes, which showed high potential in EMI shielding.

Three-Dimensional Printed Highly Porous and Flexible Conductive Polymer Nanocomposites with Dual-Scale Porosity and Piezoresistive Sensing Functions.

Highly flexible, deformable, and ultralightweight structures are required for advanced sensing applications, such as wearable electronics and soft robotics. This study demonstrates the three-dimensional (3D) printing of highly flexible, ultralightweight, and conductive polymer nanocomposites (CPNCs) with dual-scale porosity and piezoresistive sensing functions. Macroscale pores are established by designing structural printing patterns with adjustable infill densities, while the microscale pores are developed by phase separation of the deposited polymer ink solution. A conductive polydimethylsiloxane solution is prepared by mixing polymer/carbon nanotubes with non-solvent and solvent phases. Silica nanoparticles are utilized to modify the rheological properties of the ink, making direct ink writing (DIW) feasible. 3D geometries with various structural infill densities and polymer concentrations are deposited using DIW. The solvent is evaporated during a stepping heat treatment, leading to non-solvent droplet nucleation and growth. The microscale cellular network is developed by removing the droplets and curing the polymer. Up to 83% tunable porosity is achieved by independently controlling the macro- and microscale porosity. The effect of macroscale/microscale porosity and printing nozzle sizes on the mechanical and piezoresistive behavior of the CPNC structures is explored. The electrical and mechanical tests demonstrate a durable, extremely deformable, and sensitive piezoresistive response without sacrificing mechanical performance. The flexibility and sensitivity of the CPNC structure are enhanced up to 900 and 67% with the development of dual-scale porosity. The application of the developed porous CPNCs as piezoresistive sensors for detecting human motion is also evaluated.

Green preparation of carbon fiber/liquid silicone rubber composites for flexible electrode

Stretchable flexible conductive polymer composites (flexible electrodes) had become a research hot spot. In this paper, two-component room-temperature vulcanized liquid silicone rubber (LRTV) and short carbon fibers (CFs) were mixed by mechanical blending without solvent to prepare a tensile self-reply composites with high conductivity. The relationships between the average length, length distribution and content of CFs and the performance of CFs/LRTV composites were investigated. When the CFs length was 100 μm, the composites achieved a high conductivity. The composites conductivity threshold was reached when the CFs content was 3 wt%. In addition, the composites could be used as a conductor to light the bulb when the CFs content reached 8 wt%. The conductivity remained stable during cyclic stretching with a strain of 8%. The breaking and reconstruction of the internal 3D conductive network in the composites during the stretching process were discovered. The obtained results revealed that CFs/LRTV composites can be used as highly effective, flexible, stretchable electrode materials for stretchable displays, electronic skin, personalized healthcare.

Claw-shaped flexible and low-impedance conductive polymer electrodes for EEG recordings: Anemone dry electrode

Claw-shaped flexible and low-impedance conductive polymer electrodes for EEG recordings: Anemone dry electrode

Carbon‐based conductive rubber composite for 3D printed flexible strain sensors

AbstractPolymeric‐based flexible electronic devices are in high demand due to its wide range of applications. Natural rubber (NR) shows a great potential as matrix phase for flexible conductive polymer composites with its high elasticity and fatigue resistance. In this study, a new 3D printable conductive NR (CNR) composite was developed for strain sensor applications. Different contents of conductive carbon black (CCB) were mixed with NR latex to investigate the effect of the filler content on electrical and mechanical properties of the composites. The best‐known CNR composite with the CCB content of 12 phr was selected in order to produce the feedstock for the stereolithography process (SLA). The morphological, electrical, and mechanical properties of cast and 3D‐printed samples were investigated and compared. Although the 3D‐printed CNR sample had slightly lower conductivity than the cast one, it possessed comparable tensile strength and elongation at break, with values of 12.4 MPa and 703%, respectively. In addition, electrical responses of the CNR samples were investigated to demonstrate the electromechanical property of the material as a strain sensor. The 3D‐printed CNR sample exhibited the highest electromechanical sensitivity with a gauge factor (GF) of 361.4 (ε = 210%–300%) and showed good repeatability for 500 cycles. In conclusion, the development of this 3D printable functional material with great sensing capability will pave the way for innovative designs of personalized sensing textiles and other smart wearable devices.

Electromechanical Performance of Strain Sensors Based on Viscoelastic Conductive Composite Polymer Fibers.

Flexible conductive polymer composite (CPC) fibers that show large changes in resistance with deformation have recently gained much attention as strain-sensing components for future wearable electronics. However, the electrical resistance of these materials decays with time during dynamic cyclic loading, a deformation performed to simulate their real application as strain sensors. Despite the extensive research on CPC fibers, the mechanism leading to this decay in the electromechanical response under repetitive cycles remains unreported. Herein, this behavior is investigated using fiber-based strain sensors wet spun from thermoplastic polyurethane (TPU) consisting of a carbonaceous hybrid conductive filler system of carbon black (CB) and carbon nanotubes (CNTs). We found electrical viscosity to predict the observed electromechanical resistance decay. This implies that cycling these materials enables the relaxation of both the polymer chains and the conductive network. In addition, the resulting piezoresistive fibers are sensitive to deformation in the region of low strain (gauge factor of 6.0 within 3.0% strain), remain conductive under 280.5% deformation, and are stable for more than 2000 cycles. Finally, we demonstrate the potential of TPU/CB-CNT fibers as strain sensors for monitoring human motion.

A Carbon Black/Polyvinyl Alcohol-Based Composite Thin Film Sensor Integrating Strain and Humidity Sensing Using the Droplet Deposition Method

Carbon black (CB) is a low-cost and excellent conductive material, and polyvinyl alcohol (PVA) is a non-conductive material with the advantages of easy processing and high mechanical stability. Here, we report a CB/PVA-based flexible conductive polymer film suitable for small strain detection and humidity detection. Thin film is formed by depositing the CB/PVA dispersion liquid droplets on a cleaned silicon/silicon dioxide (Si/SiO2) substrate. Theoretically, CB/PVA films can be transferred or formed on other substrates, such as polydimethylsiloxane, which have the advantage of flexibility. The droplet deposition method not only enhances the controllability of the film thickness and wastage of materials, but also improves the sensitivity of the prepared film. The electrical conductivity of the CB/PVA composite film and the relationship between the resistance change and strain were measured by the four-point bending method, which showed a good gauge factor of 30 when the strain rate was 0.007%. In addition, the sensor also showed excellent sensing performance and repeatability at humidity levels ranging from 10% to 70% RH. These results demonstrate that the CB/PVA thin film prepared in this work has the advantages of a simple fabrication process, low-cost, multifunctional properties, and high device sensitivity, providing further insights for detecting minor strain and humidity.

Water-Soluble Conductive Composite Binder for High-Performance Silicon Anode in Lithium-Ion Batteries

The design of novel and high-performance binder systems is an efficient strategy to resolve the issues caused by huge volume changes of high-capacity anodes. Herein, we develop a novel water-soluble bifunctional binder composed of a conductive polythiophene polymer (PED) and high-adhesive polyacrylic acid (PAA) with abundant polar groups. Compared with conventional conductive additives, the flexible conductive polymer can solve the insufficient electrical contact between active materials and the conductive agent, thus providing the integral conductive network, which is extremely important for stable electrochemical performance. Additionally, the polar groups of this composite binder can form double H-bond interactions with the hydroxyl groups of SiO2 layers onto the silicon surface, keeping an integral electrode structure, which can decrease the continuous formation of SEI films during the repeated cycles. Benefiting from these bifunctional advantages, the Si electrodes with the composite binder delivered a high reversible capacity of 2341 mAh g−1 at 1260 mA g−1, good cycle stability with 88.8% retention of the initial reversible capacity over 100 cycles, and high-rate capacity (1150 mAh g−1 at 4200 mA g−1). This work opens up a new venture to develop multifunctional binders to enable the stable operation of high-capacity anodes for high-energy batteries.

Piezoresistive anisotropy in conductive silicon rubber/multi-walled carbon nanotube/nickel particle composites via alignment of nickel particles

Conventional piezoresistive sensors of flexible conductive polymer composites (FCPC) are mostly isotropic because of the weak controllable fabrication strategies. In this study, a facile strategy was introduced to fabricate the polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (CNT)/aligned nickel particles (Ni) composites under a low magnetic field. The PDMS pre-polymer firstly mixed with CNT and Ni particles with ultrasonic and solvent assistant, and then cured under a magnetic field with a magnetic flux density of 75 mT to form the composites. Because of the alignment of Ni particles, the PDMS/CNT/align-Ni composites exhibited obviously electrical, mechanical and piezoresistive anisotropy. Specifically, the compression modulus of the composites with 0.23 vol% CNTs and 3.93 vol% Ni particles was ∼4.93 and ∼3.66 MPa at the direction parallel to (X direction) and vertical to the alignment direction of Ni particles (Y direction), respectively. The anisotropic index of the electrical conductivity could reach 2.6 × 105 in the PDMS/CNT/aligned-Ni composites containing 0.23 vol% CNT and 3.37 vol% Ni particles. Furthermore, the PDMS/CNT/aligned-Ni composites showed a negative piezoresistive effect at X direction and a positive piezoresistive effect at Y direction.

Magnetic field-induced strategy for synergistic CI/Ti3C2T /PVDF multilayer structured composite films with excellent electromagnetic interference shielding performance

Lightweight, scalable, mechanically flexible conductive polymer composite was always desirable for electromagnetic interference (EMI) shielding applications. In this work, we showcased a novel approach to the superior EMI shielding composite materials by orchestrating the multilayered structure and synergistic system. The asymmetric structure with the carbonyl irons (CI)-rich Ti3C2Tx/poly(vinylidene fluoride) (PVDF) magneto-electric layer jointly behind the Ti3C2Tx nanosheets filled PVDF layer was designed and fabricated with the aid of a facile but efficient magnetic field-induced method and was then hot-pressed into a multilayer structured film. Ti3C2Tx nanosheets were excluded by CI agglomeration layer in the asymmetric film to form the complete 3D electrical conductive skeletons. Based on this strategy, EMI shielding properties of the asymmetric multilayer structured composite was superior to the homogeneous blend and sandwiched or alternating layered composites. In addition, an increase in CI content in the composite referred to the thickening of CI-rich layers, making it gain the most powerful EMI SE values, i.e. 42.8 dB for DCMP20–10 film (20 wt% CI, 10 wt% Ti3C2Tx) at a thickness of 0.4 mm. More importantly, the composite transformed from a reflection type to an absorption dominating EMI shielding material due to the multireflections and magneto-electric synergism in the CI-rich Ti3C2Tx/PVDF layers. Meanwhile, the EMI SE of the composites can be adjusted by increase of either theoverall thickness, or the layer numbers of m-DCMP sheets. The thickness specific EMI SE was calculated as 165.25 dB mm−1 for 4-sheet composite film, a record high value among the high efficiency polymer-based EMI shielding materials. This method offered an alternative protocol for preferential integration of excellent EMI shielding performance with high mechanical performance in CPC materials.

Study on Fault Optimization of Intermediate Joint of Power Cable

Abstract Cable joints are often prone to failure due to loose contact, small contact area and increased contact resistance, resulting in obvious heating. In the existing cable emergency repair work, the cable joints of the original section of the cable and the access end are made on site. Due to the long production time, the emergency repair speed is reduced. Therefore, this paper studies the connection mode of the new cable joint to make the contact between conductors more sufficient and the contact resistance smaller, and designs a scheme of three-phase cable plug-in intermediate joint with high safety and simple installation; at the position of cable joint, three kinds of flexible conductive polymer materials suitable for joint connection are proposed to be used at the contact gap between conductor and conductor, conductor and conductor sleeve, so as to make close contact, reduce contact resistance and further reduce the incidence of cable joint failure.

Enhanced mechanical performances and high-conductivity of rGO/PEDOT:PSS/PVA composite fiber films via electrospinning strategy

Flexible conductive polymer films with excellent mechanical performances and high conductivity are ideal materials for wave absorption, electromagnetic shielding, energy storage and electronic skin, but up to now, their preparation is still very challenging. In this work, a highly conductive reduced graphene oxide/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)/polyvinyl alcohol (rGO/PEDOT:PSS/PVA) composite fiber film was prepared by electrospinning with chemically modified rGO as additive. Compared with the traditional electrospinning technology, this experiment obtained a conductive fiber film with higher density and better filterability and ductility through the high-speed rotating turntable receiving screen. Among them, the arc tensile stress of the fiber film is 4.7 MPa, the radial elongation at break is 61.13% and the electrical conductivity can reach 1.7 S/m. Therefore, this work introduces further prospects for developing efficient conductive fiber films by feasible material selection and highly improved conductivity through special preparation methods.

A Stable Li Metal Anode with Electrochemically Treated Poly(ethylene oxide) Coating for Lithium Oxygen Batteries

Rechargeable lithium-oxygen batteries (LOBs) has being considered as one of the most promising candidates for the next-generation high energy-density batteries. The long-term cycling ability of LOBs is closely related to the stability of Li metal anode in an oxygen-rich environment. In this study, a polymer-supported solid electrolyte interphase (PS-SEI) layer generated on Li metal surface was investigated to minimize side reactions between Li metal anode and electrolyte as well as highly reactive oxygen moieties and soluble catalysts (redox mediators, RMs). The improved robustness of the PS-SEI layer can be attributed to uniformly-distributed stiff oxygen-containing components interacted with flexible ionic conductive polymer matrix. In addition, the impedance spectra of the LOBs with a PS-SEI before and after the cycling revealed a stabilized interface between Li anode and the electrolyte. The PS-SEI incresed the cycle life of LOBs by more than 50% compared to the LOBs without PS-SEI under the same testing condition of 1.0 mAh cm-2 at 0.2 mA cm-2. The combination of this protection layer and and an effective redox mediater such as (2,2,6,6-tetramethylpiperidin-1-yl) oxidanyl (TEMPO) further improved the performance of LOBs.

Flexible conductive polymer composite materials based on strutted graphene foam

Electrically conductive polymer composites (CPCs) with bendable and stretchable deformation capacity are one of key challenges for flexible cable, wearable electronics and so on. 3D graphene network is an emerging graphene bulk material beyond the pre-exiting graphene powders and films, which is also an advanced 3D-network filler instead of traditional powdery fillers, for the construction of CPCs. Herein, a strutted-graphene foam is produced at large scale, whose shape is customizably designed. The strutted graphene is further applied as the filler for making a composite. The fabricated composite shows comprehensively enhanced mechanical modulus, thermal conductivity, and electrical conductivity, which increase by 40%, 54%, and 8 orders of magnitude at a low filling fraction of 0.15 vol% of strutted graphene, respectively. The fabrication process is facile, low-cost, and scalable, which can be envisaged as a rational design and engineering of advanced polymeric composites.

Fabrication of Conductive Polymer Composites from Turkish Hemp-Derived Carbon Fibers and Thermoplastic Elastomers

In this study, carbon fibers filled flexible conductive polymer composites were fabricated. Turkish hemp was used to produce conductive carbon fibers. In order to do this, hemp fibers were carbonized under different conditions. After this step, flexible conductive composites were fabricated by using poly[styrene-b-(ethylene-co-butylene)-b-styrene] matrix and hemp-based carbon fibers. Composite films were produced by combination of solvent casting and hot pressing. Various levels of carbon fibers were used in order to determine the percolation behavior of the composites. Morphological and electrical properties of the composite films were analyzed. Electrical resistivity of the samples decreased by increasing the filler ratio.