Applications In Flexible Electronics Research Articles

Laser-Induced Silver Nanowires/Polymer Composites for Flexible Electronics and Electromagnetic Compatibility Application

Laser-Induced Silver Nanowires/Polymer Composites for Flexible Electronics and Electromagnetic Compatibility Application

Superhydrophobic, Multifunctional, and Mechanically Durable Carbon Aerogel Composites for High-Performance Underwater Piezoresistive Sensing.

Carbon aerogel piezoresistive sensors (CAPSs), owing to their good thermal stability, self-constructed conductive network, and fast response to pressure, have attracted extensive attention in the field of flexible and wearable electronics in recent years. However, it is still a great challenge for CAPSs to monitor subtle deformations and achieve high-performance underwater piezoresistive sensing. Herein, a superhydrophobic and electrically conductive carbon aerogel composite (CAC) was fabricated by the combination of fluorination of carbon aerogels and decoration of fluorinated halloysite nanotubes (HNTs). Due to the exceptional light absorption and excellent photothermal conversion performance, CAC has a fast and accurate response to temperature with a high-temperature coefficient of resistance (TCR) of -1.06%/°C. The resistance of CAC exhibits a linear response toward compressive strain up to 80% with a high gauge factor of -1.24. Significantly, the CAC sensor can effectively detect tiny deformations, thanks to its excellent waterproof performance, and it enables stable output of sensing signals in an underwater environment. This work provides new insights into the development of superhydrophobic, multifunctional, and mechanically durable piezoresistive sensors with potential applications in underwater flexible electronics.

Stereochemical Shape Morphing in Diels-Alder Polymer Networks.

The intrinsic reversibility of dynamic covalent bonding, such as the furan-maleimide Diels-Alder (DA) cycloaddition reactions, enables reprocessable, self-healing polymer materials that can be reconfigured via the mechanism of solid-state plasticity. In this work, the temperature-dependent exchange rates of stereochemically distinct endo and exo DA bonds are leveraged to achieve tunable, temperature- and stress-activated shape morphing in Diels-Alder polymer (DAP) networks. Through thermal annealing, ≈35% of endo DA isomers are converted in neat DAP networks to the thermodynamically favored exo form, achieving ≈97% exo after complete annealing at 60°C. This conversion results in a ≈1.7 fold increase in elastic modulus, from 1.7 to 3.0MPa, and significantly alters the stress relaxation and shape recovery behavior. Spatially resolved annealing, is further showcased enabling the precise control of spatial distributions of endo and exo DA bonds across planar geometries. The locally distinct concentrations of endo/exo isomers, achieved by temperature-induced conversion of endo DA isomers to the thermodynamically stable exo DA isomers, gave rise to the spatial distributions of stress relaxation rates and elastic strain recovery mismatch to enable controlled stereochemical shape morphing. This approach provides a simplified, thermally driven method for shape morphing, with potential applications in soft robotics and flexible electronics.

Informatics-based design of polyaniline-carbon nanotube thermoelectric nanocomposite using ANN and GA

Abstract Conducting polymer and carbon nanotube (CNT) based nanocomposites have emerged as prospective thermoelectric (TE) materials due to their potential application in flexible electronics. Non-conventional charge and heat transport in these nanocomposites, presents the possibility to enhance the TE conversion efficiency, given by ZT. However, the highly non-linear and complex association of structure and composition with the overall TE properties have hindered the development of any general strategy to develop high ZT nanocomposites. Here, we implement artificial neural network (ANN) and genetic algorithm (GA) to develop data driven models followed by optimization to design high efficiency nanocomposites based on CNT dispersed in polyaniline (PANI) matrix. Our models suggest that CNT concentration plays the most crucial role in determining ZT. Non-dominated Pareto optimal solutions consisting of different combinations of design variables are obtained by multi-objective optimization. Although a range of optimal solutions span over different regions of the search space, in general we note that longer CNTs boost Seebeck coefficient (S) and electrical conductivity (σ), and smaller length lowers thermal conductivity (k), while higher diameter of CNTs increase S and lowers σ and k. The results provide a general guideline for developing CNT-PANI nanocomposites with enhanced TE figure of merit.

Optoelectronic effect of Al-based buffer layers on Al-doped ZnO thin transparent conductive films on flexible substrates

AZO (Al-doped ZnO) film is a transparent conductive film that offers a simple preparation process, low cost, non-toxicity, and excellent stability. It serves as a high-quality material extensively used in liquid crystal displays, solar cells, and other fields. In this study, AZO thin films were prepared on a PET substrate with an Al2O3 buffer layer using the magnetron sputtering method. The deposition parameters were optimized through the Taguchi method and Grey Correlation Analysis. The results demonstrate that the optimal deposition parameters for achieving superior photoelectric properties during the fabrication of AZO films are 100 W (radio frequency power), 1.0 Pa (sputtering pressure), 20 min (coating time), and 20°C (substrate temperature). Furthermore, the incorporation of an Al2O3 buffer layer enhances the quality of AZO film on PET substrate. This investigation successfully deposited uniform and highly efficient AZO thin films onto flexible PET substrates at low temperatures, thereby expanding their potential applications in flexible electronics.

Facile Formation of Metallic Surface with Microroughness via Spray-Coating of Copper Nanoparticles for Enhanced Liquid Metal Wetting.

This paper presents a simple, fast, and cost-effective method for creating metallic microstructured surfaces by spray-coating a dispersion of copper nanoparticles (CuNPs) onto polymethyl methacrylate (PMMA) substrates, enabling the imbibition-induced wetting of liquid metal. The formation of these microstructured patterns is crucial for the spontaneous wetting of gallium-based liquid metals. Traditional techniques for producing such microstructures often involve complex and costly lithography and vacuum deposition methods. In contrast, this study demonstrates that liquid metal wetting can occur with metal microstructures formed through a straightforward spray-coating process. To immobilize the CuNPs on the polymer substrate, an organic solvent that dissolves the polymer surface was employed as the dispersion medium. The effects of various spray-coating parameters, including distance and time, on the uniformity and immobilization of CuNP films were systematically investigated. Under optimal conditions (120 s of spray time and 10 cm spray distance), CuNPs dispersed in dichloromethane (DCM) yielded uniform and stable microstructured surfaces. The spontaneous wetting of gallium-based liquid metal was observed on the fabricated CuNP film. Additionally, liquid metal selectively wet the CuNP patterns formed by stencil techniques, establishing electrical connections between electrodes. These findings underscore the potential of spray-coating for fabricating metallic surfaces to drive the formation of liquid metal patterns in flexible electronics applications.

3D printed conductive hydrogel based on silk fibroin and tetramer-grafted-polyethylenimine micelle for body-motion monitoring

Conductive hydrogels hold significant promise for applications in flexible wearable, soft robotics, implantable devices, and other fields, which offer distinct advantages due to their biomimetic structures, intrinsic properties, and biocompatibility. This study builds upon our previous research by fabricating a conductive hydrogel through the combination of 30 % Pluronic F127 and aniline tetramer-grafted-polyethyleneimine (AT-PEI) copolymers. To enhance the properties of hydrogels, we successfully engineered silk fibroin-based conductive hydrogels (SF-AD) by inducing the transition of silk fibroin from a random coil to a β-sheet structure using the F127 and AT-PEI/DNA complex (AD), endowing the hydrogels with dual ionic and electronic conductivity. The conductivity of all hydrogel exceeds 10−4 S/cm. Additionally, SEM was employed to characterize the pore size of the hydrogels, revealing a decrease with higher AD content. The swelling ratio ranged between 4.89 and 6.50, indicating the tunable nature of the hydrogels' structure. Utilizing 3D printing, we produced a 2 × 2 cm2 mesh active conductive layer that ensures a more uniform stress distribution—maximum sensitivity with a grid width of 4 mm. Our assembled hydrogel sensor demonstrated long-term stability in cycling tests over 1000 cycles and proved capable of recognizing various human movements. The SF-AD hydrogel, characterized by its unique combination of properties and potential for customization, presents broad prospects for future applications in flexible electronics.

Polymer Composite Coatings Enhanced with Superhydrophobic Properties for Flexible Electronics Applications: A Review

ABSTRACT Flexible electronics have revolutionized various industries by offering lightweight and conformable solutions for diverse applications. However, their vulnerability to environmental factors, particularly moisture, remains a critical challenge. Polymer composite coatings enriched with superhydrophobic properties have gained considerable attention as a promising solution to safeguard flexible electronics. The present research report is a comprehensive review of the recent advancements in the development and application of superhydrophobic polymer composite coatings in flexible electronics, highlighting its potential applications in sensors and EMI shielding. The improvement in superhydrophobic characteristics hinges upon the choice of materials, fabrication techniques, surface morphology, and topographical features. This review article elaborates on the selection criteria for various organic and inorganic fillers suitable for polymers possessing innate hydrophobic or conducting properties. The different materials used as fillers in polymer matrix for fabricating superhydrophobic coating, the factors affecting the superhydrophobic properties of surfaces, and the superhydrophobic properties of fabricated surfaces using different materials have been reported.

MgO nanofiller reinforced biodegradable, flexible, tunable energy gap HPMC polymer composites for eco-friendly electronic applications

This study explores the development and characterization of eco-friendly Magnesium Oxide (MgO) nanofiller reinforced hydroxypropyl methylcellulose (HPMC) polymer composites for eco-friendly electronic applications. The prepared nanocomposites are biodegradable and flexible without any additional plasticizer. MgO nanoparticles were synthesized using the solution combustion method and incorporated into HPMC matrix through solution casting method. The structural, mechanical, optical, AC and DC electrical, and degradation properties of the prepared nanocomposites were systematically investigated. X-ray diffraction (XRD) confirmed the successful integration of MgO nanoparticles into the HPMC matrix, with noticeable interactions affecting the crystallinity. Mechanical testing revealed an optimal MgO concentration of 0.2 g, which provided the best balance of strength and ductility, while higher concentrations led to increased brittleness. UV–Vis spectroscopy results evident that the energy gap of nanocomposites can be tuneable with MgO incorporation. The photoresponsivity study indicated that higher MgO content reduce the photocurrent due to agglomeration and defect states. Dielectric studies showed a typical frequency-dependent behaviour, with enhanced dielectric constants at lower frequencies attributed to interfacial polarization. However, increasing MgO content decreased the dielectric constant and loss due to reduced polymer chain mobility and increased resistive pathways. Current-Voltage (I-V) characteristics demonstrated a non-ohmic conduction behaviour with Poole-Frenkel emission identified as the predominant conduction mechanism. Degradation tests in both tap water and soil, demonstrated that the MgO incorporation significantly slowed the degradation rate of the composites, enhancing their durability. These findings suggest that MgO-HPMC nanocomposites hold promise for sustainable and flexible eco-friendly electronic applications.

Liquid Metal-Based Elastomer Composite with Selective Switchable Adhesion to Solids.

Selective switchable adhesion has recently attracted much attention due to its wide applications in transfer printing, information transfer, and flexible electronics. However, selective adhesive materials often have a complex adhesion or preparation process, which limits their use. To overcome this problem, this study prepares a composite of liquid metal foam and polydimethylsiloxane (PDMS) with selective photocontrolled adhesion, which can directly adhere to solids at room temperature. Utilizing the photoinduced phase transition of liquid metals, solid adhesion can be regulated by changing the backing layer modulus of the adhesive layer. Since the phase transition process is gradually completed by heat transfer from the illuminated side to the backlight side that adheres to the solid, the melting area on the backlight side can be regulated by controlling the light time, which determines the adhesion regulation area. Therefore, the accuracy of the adhesion regulation can reach less than 0.9 mm without relying on the accuracy of the infrared light. Moreover, based on the selective switchable adhesion, the selective transfer of solids with different scales can be achieved at room temperature. The findings of this study may provide strategies for the simple preparation of selective adhesive materials and the improvement of control accuracy.

Kill Two Birds with One Stone: Cracking Lithography Technology for High-Performance Flexible Metallic Network Transparent Conductors and Metallic Micronano Sheets.

Flexible electronics have sparked a wide range of exciting applications, such as flexible display technologies, lighting, sensing, etc. Flexible conductors are essential components of flexible electronics and seriously affect efficiency and overall performance. Here, a facile and kill-two-birds-with-one-stone strategy of cracking lithography technology has been proposed to simultaneously fabricate two high-performance flexible conductors, flexible metallic network transparent conductors (f-NTCs) and metallic micronano sheets (MMNSs). The PET substrate flexible transparent conductors (FTCs) based on this strategy yield 88.1% transparency within the visible spectrum and a sheet resistance of 9 Ω/sq. In addition, the FTCs show exceptional mechanical stability, with the sheet resistance remaining virtually unchanged even after 6000 s of bending tests. Subsequently, the remaining MMNSs are recycled to manufacture a Ag paste, showing a very low conductive percolation threshold (∼13%) and excellent flexibility with 140% breaking elongation. After 1000 s of stretching tests, it showed excellent mechanical stability. Furthermore, flexible electroluminescent devices based on the FTCs and sensors fabricated with MMNSs both show excellent performance, demonstrating their potential wide applications in flexible electronics.

Electrode-Dependent and Tunable Sub-to-Super-Linear Responsivity in Mott Material-Enabled Near-Infrared Photodetectors for Advanced Near-Sensor Image Processing.

Brain-like intelligence is ushering humanity into an era of the Internet of Perceptions (IoP), where the vast amounts of data generated by numerous sensing nodes pose significant challenges to transmission bandwidth and computing hardware. A recently proposed near-sensor computing architecture offers an effective solution to reduce data processing delays and energy consumption. However, a pressing need remains for innovative hardware with multifunctional near-sensor image processing capabilities. In this work, Mott material (vanadium dioxide)-based photothermoelectric near-infrared photodetectors are developed that exhibit electrode-dependent and tunable super-linear photoresponse (exponent α > 33) with ultralow modulation bias. These devices demonstrate an opto-thermo-electro-coupled phase transition, resulting in a large photocurrent on/off ratio (>105), high responsivity (≈500 A W-1), and well detectivity (≈3.9× 1012 Jones), all while maintaining rapid response speeds (τr = 2 µs and τd = 5 µs) under the bias of 1V. This electrode-dependent super-linear response is found to arise from the electron doping effect determined by the polarity of the Seebeck coefficient. Furthermore, the work showcases intensity-selective near-sensor processing and night vision pattern reorganization, even with noisy inputs. This work paves the way for developing near-sensor devices with potential applications in medical image preprocessing, flexible electronics, and intelligent edge sensing.

Nitrogen Doping Engineering of V2CTx based Zinc Ion Hybrid Microcapacitors with Quadruple High Energy Density

To accommodate the long-term and stable energy supply requirements for wearable electronics, the reported flexible zinc ion hybrid microcapacitor (ZIHMC) needs to further increase the energy density. So, a nitrogen doped V2CTx (N-V2CTx) based ZIHMC was proposed to achieve high electrochemical performance. The introduction of N heteroatoms by NH3 annealing can dramatically increase the electrical conductivity of V2CTx and simultaneously widen the voltage window to 1.9 V. In detail, the doped nitrogen atoms in V2CTx based device has a maximum capacity of 293.0 mF cm–2, four times higher than that of pure V2CTx based ZIHMC. The mechanism of the enhanced electrochemical performance by nitrogen doped V2CTx was revealed by the experimental analysis and theoretical simulation. And the N-V2CTx based ZIHMC demonstrated high energy density with 150.0 μWh cm–2 at a power density of 380.0 μW cm–2 and excellent stability with 94.80% capacitance retention after 3000 charge-discharge cycles. The N-V2CTx based ZIHMC also presents excellent flexibility without virtually capacity loss after 3000 bending cycles. The good electrochemical performance and flexibility of N-V2CTx ZIHMC make it has potential applications in flexible wearable electronics.

Room temperature self-healing and reprocessing elastomer with dynamic bonds for flexible wearable sensor

The production of room-temperature (RT) self-healing elastomers with good mechanical properties is significant for application in soft electronics, yet remains a challenge in material design. Herein, we present an effective and feasible approach to create RT self-healing cross-linked elastomers (CEs) through photo-initiated copolymerization. A key feature is the incorporation of 2,7-dihydroxynaphthalene and alicyclic diisocyanate into the polymer backbone as hard domains, along with the rational optimization of the soft segments. In addition, urethane-based H-bonding interactions, acting as sacrificial bond, contribute to the high toughness of the CEs. The resulting CEs exhibit desirable mechanical performances, including a tensile strength of 12.9 MPa, an elongation at break of approximately 1243 %, and a high toughness of 68.64 MJ m–3. Furthermore, by integrating a flexible PTMEG-based polymeric chain and hindered urea bonds into the backbone, the chain mobility and dynamic nature of the CEs are improved. The CEs are capable of reprocessing and self-healing at RT within 30 min upon scratching, with a self-healing efficiency in toughness reaching 99.64 %. The dynamic networks are evidenced by rheological test, stress relaxation analysis, as well as creep and recovery experiments. These CEs, characterized by their superior properties, hold promise for applications in flexible wearable electronics.

Evaluating the mechanical stability and flexibility of Ga2O3 films on mica substrates via Pulsed Laser deposition and CASTEP simulations

This research analyzes the mechanical stability and flexibility of Ga2O3 films on mica substrates, advancing material science. Integrating Cambridge Sequential Total Energy Package (CASTEP) simulations with Pulsed Laser Deposition (PLD) reveals β-Ga2O3′s electronic structure and wide bandgap of 4.98 eV. X-ray diffraction (XRD) analysis indicates a significant increase in crystallite size from 26 nm to 152 nm as the substrate temperature increased from 500 °C to 800 °C. Scanning Electron Microscopy (SEM) images show enhanced grain size and defined boundaries at higher temperatures. The mechanical properties, including a bulk modulus of 201.35 GPa, shear modulus of 97.52 GPa, and Young’s modulus of 251.90 GPa, confirm the material’s strong mechanical stability. These properties suggest that Ga2O3 films suit high-stress and flexible electronic applications. This study bridges theoretical predictions with empirical observations, contributing to developing Ga2O3-based materials for next-generation technologies. © 2017 Elsevier Inc. All rights reserved.

Supercapacitor electrodes based on Ru/RuO2 decorated on N,S-doped few-layer graphene

Innovatively designed flexible and high-performance shape memory polymer supercapacitors are promising next-generation energy storage devices for portable and wearable electronics. Therefore, thermally induced smart shape memory polymer polyurethane was synthesized using polycaprolactone/poly(ethylene glycol)/hexamethylene diisocyanate (PCL/PEG/HDI) in which the incorporation of PEG successfully assisted in lowering the transition temperature. The resulting polymer exhibits a remarkable transition temperature of 50 °C and a shape recovery ratio of 100 % at a strain of 300 %. The smart polymer was coated with a silver paste to ease the electron flow followed by coating with the electrode. Hybrid electrode materials are prepared in two stages. Initially, a few layers of holey-graphene were synthesized, where BET surface area reveals the presence of pores that are tuned by isothermal treatments in O2-atmosphere. Subsequently, active hybrid electrode materials nanostructured Ru/RuO2 decorated N, S-doped few layers of holey graphene were synthesized using hydrothermal methods. Here, nitrogen and sulfur doping in the basal or edge plane served as catalysts and metal coordination sites, facilitating the uniform distribution of ruthenium nanoparticles on the graphene. It is further confirmed by the density function theory (DFT) calculation using the adsorption energy. The optimized hybrid electrode material demonstrates a specific capacitance of 1297 mFcm−2 at a current density of 2 mAcm−2. A flexible-shape memory polymer supercapacitor exhibits a notable device-specific capacitance of 189 mFcm−2 at a current density of 1 mAcm−2, a high energy density of 45 µWhcm−2 at a power density of 0.25 mWcm−2, with 81 % of specific capacitance retention after eight shape programming and recovery cycle. Excellent shape recoverability and robust electrochemical performance make the as-fabricated symmetric supercapacitors a promising candidate for integration in flexible electronic applications.

A highly stretchable and self-adhesive cellulose complex hydrogels based on PDA@Fe3+ mediated redox reaction for strain sensor

As the application of conductive hydrogels in the field of wearable smart devices is gradually deepening, a variety of hydrogel sensors with high mechanical properties, strong adhesion, fast self-healing, and excellent conductivity are emerging. However, it is still a great challenge to manufacture hydrogel sensors combining multiple properties. Herein, we leveraged the dynamic redox reaction occurring between polydopamine (PDA) and Fe3+ to induce ammonium persulfate (APS) to generate free radicals, thereby initiating the copolymerization of hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) monomers. Then, polypyrrole-encapsulated cellulose nanofibers (PPy@CNF) and carboxymethylcellulose (CMC) were incorporated as conductive reinforced nanofillers and interpenetrating network skeleton. The obtained hydrogel cross-linked through reversible metal-ligand bonds, π-π stacking and abundant hydrogen bonding demonstrated great mechanical properties (strength 240.4 kPa, strain 1175 %) and self-healing ability (88.96 %). Particularly, the gel displayed ultrahigh durability and skin adhesive ability (75 kPa after 10 cycles), surpassing previous skin adhesion hydrogels. Furthermore, through the synergistic conductive effect of PPy@CNF and Fe3+, the prepared hydrogel sensor possessed high sensitivity (GF = 1.89) with a wide sensing range (~1000 %), which could realize the human body's daily motion detection, and had a promising application in flexible wearable electronics.

Graphene oxide dispersed rose-petals based green chemistry synthesis of hybrid composite for novel spectroscopic applications

Rosa Santana family includes the rose, a highly prized decorative plant having symbolic, cultural, and commercial value. The exploration of graphene-based nanocomposites has expanded significantly, with recent research focusing on integrating these materials into natural and sustainable matrices. This study investigates the dispersion of graphene oxide (GO) within the biological structure of rose-petals, representing a novel approach to developing eco-friendly nanocomposites. The rich colours of the roses are ascribed to pigments such as flavanols, carotenoids, and anthocyanin. Carotenoids, which are found in natural colours including yellow, orange, violet, as well as another ingredient found in rose petals. By leveraging the inherent properties of rose petals, such as their unique properties and surface morphology and biocompatibility, this work highlights the potential of GO to enhance the mechanical, electrical, and optical characteristics of the composite. Advanced characterization techniques, including scanning electron microscopy (SEM), and electrochemical analysis, are employed to understand the interaction between GO and the rose petal substrate. The techniques of FT-IR, EDS, XRD, SEM, energy band gap, and CV were used in characterize the synthesis of doped graphene using rose petals extract. The findings underscore the synergistic effects of this natural-synthetic hybrid system, opening pathways to innovative applications in flexible electronics, biosensors, and sustainable material design. The novelty of this research lies in its foundational exploration of integrating graphene oxide with organic substrates like rose petals, offering a new direction for the development of environmentally benign graphene nanocomposites. Green chemistry based novel nanocomposite may open up new avenues for production of graphene oxide homogenious dispersion with rose-petal extract.

3D Network of Liquid Metal-Embedded Graphene via Surface Coating for Flexible Thermal Management.

The rapid growth of flexible electronics has led to significant demand for relevant accessories, particularly highly efficient flexible heat dissipators. The fluidity of liquid metal (LM) makes it a candidate for realizing flexible thermal interface materials (TIMs). However, it is still challenging to combine LM with a conductive thermal network to achieve the synchronous improvement of thermal conductivity and flexibility. In this work, highly conductive flexible LM@GN/ANF films are made by coating LM nano-droplets with graphene nanosheets (GN) via sonication, and then they are combined with aramid nanofibers (ANF). The LM@GN/ANF film is found to have a thermal conductivity of 5.67Wm-1K-1 and a 24.5% reduction in Young's modulus, making it suitable for various flexible electronic applications such as wearable devices and biosensors.

Corrosion and conductivity damage of AgNW transparent conductive thin films under a simulated sulfur-containing atmosphere and mechanical force

Silver nanowire (AgNW) transparent conductive thin films possess high flexibility, high conductivity, high light transmittance and etc., demonstrating significant advantages in flexible electronics applications. However, in the service occasions, the coupled effect of corrosion and mechanical force easily makes the electrical conductivity of AgNW films deteriorate or even fail, which seriously affects the service reliability of AgNW films. In this work, scanning vibrating electrode technique was firstly used to confirm the existence of electrochemical corrosion on AgNW films. Furthermore, electrochemical measurements (including OCP, PDP and EIS) were carried out for researching the electrochemical corrosion process on AgNW films under different environmental factors and mechanical forces. Their surface morphologies and electrical conductivity were characterized and evaluated by the Scanning Electron Microscopy and square resistance tester respectively. Experimental results indicate that the corrosion-mechanics interaction effect aggravates the damage process of electrical conductivity of AgNW films.