Electrical and Thermal and Self-Healing Properties of Graphene-Thermopolyurethane Flexible Conductive Films

Preparation of CNT/CNF/PDMS/TPU Nanofiber-Based Conductive Films Based on Centrifugal Spinning Method for Strain Sensors

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors.

Polyurethanes Modified by Ionic Liquids and Their Applications

Polyurethane (PU) refers to the polymer containing carbamate groups in its molecular structure, generally obtained by the reaction of isocyanate and alcohol. Because of its flexible formulation, diverse product forms, and excellent performance, it has been widely used in mechanical engineering, electronic equipment, biomedical applications, etc. Through physical or chemical methods, ionic groups are introduced into PU, which gives PU electrical conductivity, flame-retardant, and antistatic properties, thus expanding the application fields of PU, especially in flexible devices such as sensors, actuators, and functional membranes for batteries and gas absorption. In this review, we firstly introduced the characteristics of PU in chemical and microphase structures and their related physical and chemical performance. To improve the performance of PU, ionic liquids (ILs) were applied in the processing or synthesis of PU, resulting in a new type of PU called ionic PU. In the following part of this review, we mainly summarized the fabrication methods of IL-modified PUs via physical blending and the chemical copolymerization method. Then, we summarized the research progress of the applications for IL-modified PUs in different fields, including sensors, actuators, transistors, antistatic films, etc. Finally, we discussed the future development trends and challenges faced by IL-modified PUs.

The mechanical, optical, and thermal properties of graphene influencing its pre-clinical use in treating neurological diseases

Rapid progress in nanotechnology has advanced fundamental neuroscience and innovative treatment using combined diagnostic and therapeutic applications. The atomic scale tunability of nanomaterials, which can interact with biological systems, has attracted interest in emerging multidisciplinary fields. Graphene, a two-dimensional nanocarbon, has gained increasing attention in neuroscience due to its unique honeycomb structure and functional properties. Hydrophobic planar sheets of graphene can be effectively loaded with aromatic molecules to produce a defect-free and stable dispersion. The optical and thermal properties of graphene make it suitable for biosensing and bioimaging applications. In addition, graphene and its derivatives functionalized with tailored bioactive molecules can cross the blood-brain barrier for drug delivery, substantially improving their biological property. Therefore, graphene-based materials have promising potential for possible application in neuroscience. Herein, we aimed to summarize the important properties of graphene materials required for their application in neuroscience, the interaction between graphene-based materials and various cells in the central and peripheral nervous systems, and their potential clinical applications in recording electrodes, drug delivery, treatment, and as nerve scaffolds for neurological diseases. Finally, we offer insights into the prospects and limitations to aid graphene development in neuroscience research and nanotherapeutics that can be used clinically.

An Overview of Self-Healable Polymers and Recent Advances in the Field

The search for materials with better performance, longer service life, lower environmental impact, and lower overall cost is at the forefront of polymer science and material engineering. This has led to the development of self-healing polymers with a range of healing mechanisms including capsular-based, vascular, and intrinsic self-healing polymers. The development of self-healable systems has been inspired by the healing of biological systems such as skin wound healing and broken bone reconstruction. The goal of using self-healing polymers in various applications is to extend the service life of polymers without the need for replacement or human intervention especially in restricted access areas such as underwater/underground piping where inspection, intervention, and maintenance are very difficult. Through an industrial and scholarly lens, this paper provides (a) an overview of self-healing polymers, (b) classification of different self-healing polymers and polymer-based composites, (c) mechanical, thermal, and electrical analysis characterization, (d) applications in coating, composites, and electronics, (e) modeling and simulation, and (f) recent development in the past 20 years . This review highlights the importance of healable polymers for an economically and environmentally sustainable future, the most recent advances in the field, and current limitations in fabrication, manufacturing, and performance. This article is protected by copyright. All rights reserved.

Self-Healing Silver Nanowires and Reduced Graphene Oxide/Polyurethane Composite Film Based on the Diels–Alder Reaction under Infrared Radiation

The hybrid composite of silver nanowires (AgNWs) and reduced graphene oxide (RGO) was synthesized in situ by an improved polyol–thermal method. The AgNWs-RGO with mass contents of 5–37 wt% was added into the thermo-reversible Diels–Alder reaction polyurethane (DA-PU) matrix with the AgNWs as the main conductor and the RGO as the auxiliary conductor to prepare self-healing composite conductive films. Further, the electrical conductivity, thermal conductivity, mechanical properties, infrared thermal response, and self-healing property of the composite film under infrared light irradiation were studied. The experimental results demonstrate that the AgNWs-RGO endows the composite film with good electrical and thermal conductivity and infrared thermal response ability, while the mechanical properties of the composite film decrease as the AgNWs-RGO mass content increases. The self-healing efficiency of the composite film is higher than that of the pure DA-PU under infrared light irradiation due to the good infrared photothermal response ability of the AgNWs-RGO. When the mass content of AgNWs-RGO in the composite film was 25 wt%, the AgNWs-RGO showed good dispersion in composite films, and the resistivity, thermal conductivity, and tensile strength of the composite film were 0.544 Ω·m, 0.3039 W·m⁻¹·K⁻¹, and 9.05 MPa, respectively. The infrared photothermal conversion temperature of the composite film is 158.5 °C (3450 lux for 1 min), and the infrared photothermal self-healing efficiency is 118% (3450 lux for 600 s). The AgNWs-RGO also improves the multiple self-healing ability of the composite film. The use of a high mass content of AgNWs-RGO in the composite film is beneficial in obtaining high multiple self-healing efficiencies. The first and the fifth infrared thermal self-healing efficiencies of the composite film with AgNWs-RGO of 35 wt% are 105% and 86%, respectively, and the resistivity of the composite film changes little and still maintains good conductivity.

Near-Infrared-Light-Assisted Self-Healing Graphene-Thermopolyurethane Composite Films

Graphene-thermopolyurethane (G-TPU) composite films were fabricated and the effects of the TPU initial concentration, characteristics of TPU, and graphene loading on the electrical, mechanical, thermal, infrared thermal response and near-infrared-light-assisted self-healing properties of the composite films were investigated in detail. The experimental results demonstrate that the comprehensive performances of the composite film are related to the initial concentration of the TPU solution and the characteristics of the TPU and the graphene loading. The composite film prepared from TPU solution with low initial concentration can have conductivity under the condition of low graphene content. However, the composite film prepared with appropriate initial concentration of TPU solution and high graphene loading is conducive to obtain high conductivity. After 60 s of near-infrared illumination, the temperature of the composite film first increases and then decreases with the increase in graphene loading until it reaches saturation. The near-infrared light thermal response of the composite film with high graphene loading is related to the initial concentration of TPU solution, while the near-IR thermal response of the composite film with low graphene loading is independent of the initial concentration of TPU. The surface micro-cracks of the composite film almost disappeared after 10 min of near-infrared illumination. The resistance of the conductive composite film increases after healed. The composite film prepared with low melting point TPU is more favorable to obtain high near-IR thermal self-healing efficiency.

Minireview on Self-Healing Polymers: Versatility, Application, and Prospects

Nature is blessed with self-healing properties. Mimicking nature is a traditional practice to innovate new classes of materials for researchers. In this practice, researchers made a revolutionary approach to innovate self-healing polymer (SHP) that can be used to treat damage-related losses. Different SHPs with various properties have been developed for a wide range of applications. SHPs unlocked the key to the taste of real life through their application and versatility in the sectors close to our day-by-day life of this age and the near future. In this study, we reviewed the scopes and prospects of the application of SHPs owing to different properties. Varieties of amazing properties made SHPs fit in different sectors such as construction, paint and coat, electronics, healthcare, textile, and automotive and aerospace. Similarly, due to having suitable functionality, SHPs can also be used in different industries. Therefore, it is high time to generalize the production of SHPs by suitable research and make sure the easy application for the welfare of human civilization and other living creatures.

Inkjet Printing of Flexible Transparent Conductive Films with Silver Nanowires Ink

The inkjet printing process is a promising electronic printing technique for large-scale, printed, flexible and stretchable electronics because of features such as its high manufacturing speed, environmental friendliness, simple process, low cost, accurate positioning, and so on. As the base material of printed conductive patterns, conductive ink is the foundation of the development of printed electronics technology, and directly affects the performance and the quality of electronic products. In this paper, conductive ink with silver nanowires (AgNWs) was prepared, with AgNWs of lengths of 2–5 µm and diameters of 20 nm or so, isopropyl alcohol and ethylene glycol as the mixed solvents, and modified polysilane as the wetting agent. We discussed the relationship between the formula of the AgNWs ink and the surface tension, viscosity, contact angle between ink droplet and poly(ethylene) terephthalate (PET) surface, as well as the film-forming properties of the ink. Further, we analyzed the effects of the number of printed layers and the ink concentration of the AgNWs on the microstructures, photoelectric properties and accuracy of the printed patterns, as well as the change in the sheet resistance of the film during different bending cycles. The experimental results show that flexible transparent conductive patterns with a light transmittance of 550 nm of 83.1–88.4% and a sheet resistance of 34.0 Ω∙sq⁻¹–78.3 nm∙sq⁻¹ can be obtained by using AgNWs ink of 0.38 mg∙mL⁻¹ to 0.57 mg∙mL⁻¹, a poly (ethylene terephthalate) (PET) substrate temperature of 40 °C, a nozzle temperature of 35 °C, and heat treated at 60 °C for 10 min. These performances indicate the excellent potential of the inkjet printing of AgNWs networks for developing flexible transparent conductive film.

Self-Healing Polymer Nanocomposite Materials by Joule Effect

Nowadays, the self-healing approach in materials science mainly relies on functionalized polymers used as matrices in nanocomposites. Through different physicochemical pathways and stimuli, these materials can undergo self-repairing mechanisms that represent a great advantage to prolonging materials service-life, thus avoiding early disposal. Particularly, the use of the Joule effect as an external stimulus for self-healing in conductive nanocomposites is under-reported in the literature. However, it is of particular importance because it incorporates nanofillers with tunable features thus producing multifunctional materials. The aim of this review is the comprehensive analysis of conductive polymer nanocomposites presenting reversible dynamic bonds and their energetical activation to perform self-healing through the Joule effect.

Influence of Characteristics of Thermoplastic Polyurethane on Graphene-Thermoplastic Polyurethane Composite Film

Graphene-thermoplastic polyurethane (G-TPU) composite films were fabricated by traditional blending method and tape casting process with commercial graphene sheets as functional fillers and TPU masterbatches of four different melting points as matrix, respectively. The effects of matrix on the distribution of graphene, the electrical conductivity, and infrared (IR) light thermal properties of the G-TPU composite films were investigated. The experimental results reveal that the characteristics of TPU has little influence on the electrical conductivity of the G-TPU composite films, although the four TPU solutions have different viscosities. However, under the same graphene mass content, the thermal conductivity of four G-TPU composite films with different melting points is significantly different. The four kinds of G-TPU composite films have obvious infrared (IR) thermal effect. There is little difference in the temperatures between the composite films prepared by TPU with melting a point of 100 °C, 120 °C, and 140 °C, respectively; however, when the content of graphene is less than 5 wt%, the temperature of the composite film prepared by TPU with a melting point of 163 °C is obviously lower than that of the other three composite films. The possible reason for this phenomenon is related to the structure of TPU.

High Performance of Thermoplastic Polyurethane-Graphene Oxide Self-Healing Composite Film

Graphene oxide (GO) sheets were dispersed into N, N-dimethylformamide (DMF) solution by ultrasonication and then mixed with thermoplastic polyurethane (TPU) solution uniformly, and further fabricated to GO-TPU film by casting process. The thermal properties, infrared photothermal response, and self-healing performance of the GO-TPU film were systematically investigated. The experimental results demonstrate that the thermal conductivity of GO-TPU film with 4 wt % GO and the initial concentration of 20 wt % TPU is 0.3719 W·m−1·K−1, which is 83.8% increase compared to pure TPU. The GO-TPU film has excellent infrared light-to-heat conversion efficiency. The infrared light-to-heat conversion efficiency of the GO-TPU film with 7 wt % GO and the initial concentration of 20 wt % TPU reaches the maximum, and the temperature increased by 63% compared to pure TPU, reaching 165.6 °C. The scratches on the GO-TPU composite film can be completely healed after being irradiated by infrared light for 10 min, which shows that the GO-TPU composite film has good self-healing properties.