Applications In Flexible Electronics Research Articles

Tailoring Electrical Properties in Carbon Nanomaterial Patterns with Multimaterial Aerosol Jet Printing.

Multimaterial aerosol jet printing offers a unique capability to freely mix inks with different chemical compositions in the aerosol phase, enabling one-step digital fabrication with tailored compositions or functionally graded structures, including in the x-y plane. Here, in situ mixing of two carbon nanomaterial inks with distinct electrical properties is demonstrated. By tailoring the mixing ratio of the constituent inks, electrical conductivity is modulated by 130×, and sheet resistance values for a single pass span approximately 2 orders of magnitude. The ability to manufacture components with tailored electrical properties offers significant value for hybrid and flexible electronic device applications, such as microelectronics packaging. Moreover, grading properties within a part provides a new dimension of design freedom for complex assemblies.

Investigating the role of 3D hierarchical Ni-CAT/NiFe-LDH/CNFs in enhancing the oxygen evolution reaction and Zn-air battery performance

NiFe layered double hydroxide (NiFe-LDH) is an efficient and widely available catalyst for the oxygen evolution reaction (OER), but further improvement of its OER property remains a challenge. Therefore, a conductive Ni-organic framework is triumphantly synthesized in-situ on NiFe-LDH/carbon nanofibers (Ni-CAT/NiFe-LDH/CNFs) through a hydrothermal treatment. This configuration utilizes the exposed surface area and the electron transfer pathways of Ni-CAT and CNFs, resulting in exceptional OER kinetics in alkaline conditions. A low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 79 mV dec−1 are achieved. The liquid-state Zn-air batteries, featuring Ni-CAT/NiFe-LDH/CNFs catalyst as an air cathode, indicate a significant peak power density of 292.1 mW cm−2 and an extended cycle durability of over 66 h. Solid-state Zn-air batteries demonstrate stable cycling at various flat/bent/flat states, showing great potential for flexible electronic device applications. According to experimental measurements and computational analysis, the in-situ growth of Ni-CAT on the NiFe-LDH matrix can optimize intermediate adsorption and alter hydrophilicity, resulting in improved performance of Zn-air batteries.

Unlocking the Power of Multicatalytic Synergistic Transformation: toward Environmentally Adaptable Organohydrogel.

A sustainable and efficient multicatalytic chemical transformation approach is devised for the development of all-biobased environmentally adaptable polymers and gels with multifunctional properties. The catalytic system, utilizing Lignin aluminum nanoparticles (AlNPs)-aluminum ions (Al3+ ), synergistically combines multiple catalytic cycles to create robust, mechanically stable, and versatile organohydrogels. Single catalytic cycles alone fail to achieve desired results, highlighting the importance of cooperatively combining different cycles for successful outcomes. The transformation involves free radical crosslinking, reversible quinone-catechol reactions, and an autocatalytic mechanism, resulting in a dual crosslinking strategy that incorporates both covalent and ionic crosslinking. This approach creates a dynamic gel system with combined energy dissipation and storage mechanisms. The engineered organohydrogels demonstrate vital multifunctionalities such as good thermal stability, self-healing, and adhesive properties, flame-retardancy, mechanical resilience and durability, conductivity, viscoelastic properties, environmental adaptability, and resistance to extreme conditions such as freezing and drying. The developed catalytic technology and resulting gels hold significant potential for applications in flexible electronics, energy storage, actuators, and sensors.

Fatigue life of silver thin film on pet substrate under electrical current for flexible electronics applications

Fatigue life of silver thin film on pet substrate under electrical current for flexible electronics applications

Tailoring fractal structure via 3D printing to achieve flexible stretchable electrodes based on Ecoflex/CNT/CF

Flexible electrodes are crucial for the widespread application of flexible electronics. Flexible stretchable electrodes are a research hotspot for finding a solution for the inability of flexible electrodes to withstand large deformations. In this study, the suitability of silicone rubber (Ecoflex), carbon nanotube (CNT), and carbon fiber (CF) composite materials for flexible devices and their ratios were evaluated for the first time. 3D-printed electrodes based on fractal structures with tensile insensitivity and high linearity were prepared to achieve integrated stretching of flexible devices. To demonstrate the benefits and impact of fractal structures on electrode performance, we fabricated flexible stretchable electrodes with four distinct designs: horseshoe, U-shaped, rectangular, and triangular. The tensile properties of these structures were theoretically calculated and validated through simulations and experiments; the horseshoe design proved to be the softest. Furthermore, we evaluated the performance of the prepared third-order flexible stretchable electrodes for gas-detection applications and achieved promising results, demonstrating the significant potential of these electrodes for wearable gas detection.

Self-Driven Gr/WSe2/Gr Photodetector with High Performance Based on Asymmetric Schottky van der Waals Contacts.

Two-dimensional (2D) self-driven photodetectors have a wide range of applications in wearable, imaging, and flexible electronics. However, the preparation of most self-powered photodetectors is still complex and time-consuming. Simultaneously, the constant work function of a metal, numerous defects, and a large Schottky barrier at the 2D/metal interface hinder the transmission and collection of optical carriers, which will suppress the optical responsivity of the device. This paper proposed a self-driven graphene/WSe2/graphene (Gr/WSe2/Gr) photodetector with asymmetric Schottky van der Waals (vdWs) contacts. The vdWs contacts are formed by transferring Gr as electrodes using the dry-transfer method, obviating the limitations of defects and Fermi-level pinning at the interface of electrodes made by conventional metal deposition methods to a great extent and resulting in superior dynamic response, which leads to a more efficient and faster collection of photogenerated carriers. This work also demonstrates that the significant surface potential difference of Gr electrodes is a crucial factor to ensure their superior performance. The self-driven Gr/WSe2/Gr photodetector exhibits an ultrahigh Ilight/Idark ratio of 106 with a responsivity value of 20.31 mA/W and an open-circuit voltage of 0.37 V at zero bias. The photodetector also has ultrafast response speeds of 42.9 and 56.0 μs. This paper provides a feasible way to develop self-driven optoelectronic devices with a simple structure and excellent performance.

Evaluation of thermal stresses on thin Al and AZO films deposited on polyethylene terephthalate substrates for flexible electronics applications

Thin aluminum (Al) films are widely used in electronic devices and flexible photovoltaics. In a similar capacity, Aluminum Doped Zinc Oxide (AZO) serves the same purpose. This study examines the sensitivity of both films to thermal stresses when sputtered onto Polyethylene Terephthalate substrates. These stresses include a constant temperature of 100 °C and temperature fluctuations ranging from 0 °C to 100 °C. The resistance of the films was affected by isothermal aging, but not by thermal cycling. Interestingly, thermal cycling led to microcracks in the film, while isothermal aging resulted in a slight increase in bonding and oxygen content in the Al films. For AZO films, imaging did not reveal any noticeable changes in morphology. However, both thermal cycling and isothermal aging led to a minor increase in the resistance of AZO films. These findings highlight the pronounced impact of thermal stress on the performance and structural integrity of both thin films.

Development and characterization of a highly sensitive magnetic electronic skin for intelligent manipulators

A magnetic electronic skin (e-skin) with high sensitivity, flexibility, and wide force measurement range was designed. The e-skin includes a top magnetic film layer, a middle polydimethylsiloxane (PDMS) layer and a bottom tunneling magnetoresistive sensor layer. The magnetic film layer is composed of neodymium-iron-boron particles (Nd2Fe14B) and PDMS. A test platform was established. The test results showed that the e-skin could measure forces in the range of 0.05–20 N, with a static sensitivity of 287 mV/N within 0–1 N, followed by a gradual decrease in sensitivity with an increase in static force. The resolution of the electronic skin was 0.05 N, and the change in sensitivity under dynamic force was less than 3.17 %. The response time and recovery time were 41 ms and 40 ms, respectively. This study provides a foundation for further research and development of advanced electronic skins for use in a variety of flexible electronic applications.

Bending behavior of diamane and twisted bilayer graphene: Insights from four-point bending deformation

The intriguing physical properties of two-dimensional (2D) nanomaterials make them promising building blocks for flexible electronics. Using a four-point bending approach, this work establishes a comprehensive understanding of the bending behavior of diamane – a 2D diamond nanostructure, from elastic deformation to structural failure through atomistic simulations. The four-point bending method accurately reproduces the pure bending of the sample, and the obtained force-displacement curve fit well with the classical Euler beam theory. Structural failure is observed from diamane under bending when its thickness or the number of layers increases. Atomic insights reveal that the crack initiates from the tension side of the sample, resulting in a tension-induced bending failure. Specifically, the bending limit is found to be slightly larger than the fracture strain under tensile deformation. Additionally, the bending behaviour of the diamane analogous – twisted bilayer graphene with interlayer-bonding (TBGIB), has been investigated. Different from diamane, TBGIB bends elastically at the initial stage and then experiences structural failures with increasing bending strain. Higher interlayer bonding density is observed to result in a higher bending stiffness. Meanwhile, significant interlayer shear strain is detected during bending, which leads to interlayer bond breakage, rippling, and buckling of the graphene layer. This work provides a full description of the pure bending behavior of diamane and its analogous structure, which could be beneficial for their applications in flexible electronics.

Highly flexible and transparent electrodes for high-performance thin-film heaters with nanostructured micromesh Cu–Ag ultrathin films

Herein, we present a facile method to fabricate transparent, flexible, and high-performance thin-film heaters (TTFHs) based on nanostructured micromesh (NSMM) Cu–Ag/indium tin oxide bilayer transparent thin-film electrodes (TTFEs) with both nano- and microstructures. Our approach combines Ar-assisted thermal evaporation and pulsed laser ablation techniques to fabricate NSMM TTFEs with a low sheet resistance (∼2.1 Ω/sq) and high optical transmittance (∼80.1 %). By adjusting the spacing of microholes, we can achieve excellent figure of merit values (∼51.8 × 10−3 Ω−1) for the NSMM TTFEs. These electrodes also show excellent durability and flexibility, as evidenced by a resistance change of only 4 %–18 % in cyclic bending tests with up to 200,000 cycles. Finally, we demonstrate that the NSMM TTFEs can be used as high-performance TTFHs with short response times (3.97 s at a steady temperature of 87.5 °C under low-voltage operation (5 V)) and infrared shielding properties. Our results suggest that the Cu–Ag-alloy-based NSMM TTFEs are promising transparent electrodes for various applications in flexible electronics, smart windows, and wearable devices.

Monitoring Soft Shape Surface Deformation via Optical Images for the Distinction of Contact State

The deformability of elastomer surfaces offers the opportunity to capture multimodal physical information, which opens up possibilities for applications in intelligent interactive systems and flexible electronics. Accurately identifying the surface deformation of elastomers has been a key issue for understanding the contact state in a soft touch. However, effective monitoring of the deformed surface topography during soft‐touch processes is difficult due to the complexity of interfacial deformation. Herein, the optical detection method based on an ideal diffuse reflection model is proposed to monitor the deformation of the elastomer, enabling the acquisition of a spatially continuous deformation of the surface in a soft touch. This optical system with the parallel incident light can distinguish the elastomers’ surface deformation field by constructing the correlation between the reflected light irradiance and the surface deformation angle. This method allows for the perception of the contact area. Through the deep learning method, the recognition rate can reach more than 84.24% when there are slight differences in the contact of objects with different geometric shapes. The design offers valuable insights for contact state detection tasks and facilitates soft‐touch sensing functions through the high precision of optical signal acquisition.

Self-Assembled La0.67Sr0.33MnO3:CeO2 Vertically Aligned Nanocomposite Thin Films on Flexible Mica

Vertically aligned nanocomposite (VAN) thin film has attracted tremendous research interests owing to its multifunctionality, enhanced physical properties and multi-field coupling. However, VAN has rarely been demonstrated in flexible form, which hinders its further application in flexible devices. In this work, La0.67Sr0.33MnO3-CeO2 (LC) VAN film has been deposited on flexible mica with or without a buffer layer. The LC nanocomposite films show high quality following textured growth and form a typical, vertically aligned nanostructure. Magnetic, transport and magnetoresistance properties have been explored for flexible nanocomposite thin films. Furthermore, flexible LC films maintain their properties after numerous mechanical bending tests, presenting promising future applications in flexible electronics and spintronics.

Advancements in Conductive Cotton Thread-Based Graphene: A New Generation of Flexible, Lightweight, and Cost-Effective Electronic Applications

Conductive threads have emerged as a highly promising platform for the advancement of smart textiles, enabling the integration of conductivity into fabric materials. In this study, we present a novel approach to fabricate highly flexible graphene-based smart threads, which exhibit exceptional electrical properties. Four distinct types of smart threads were meticulously prepared by drop-casting graphene dispersions onto cotton threads, utilizing various solvents. The influence of annealing temperature and the quantity of dispersed graphene on the electrical conductivity of the threads was systematically investigated. Our findings reveal that the electrical conductivity of the threads is significantly influenced by the type of solvent and the annealing temperature, while exhibiting an increasing trend with higher amounts of dispersed graphene. Remarkably, we achieved a maximum electrical conductivity of 2505.68 S cm−1 for a thread prepared with 6 mL of graphene dispersed in ethanol, annealed at a temperature of 78 °C. Furthermore, the fabricated smart threads were successfully employed as replacements for electric cables in a mobile charger and a computer mouse, demonstrating their high efficiency. This work represents a significant advancement in the development of a new generation of smart textiles, offering a simple, cost-effective, and environmentally friendly fabrication method for the production of smart threads.

Localized fabrication of flexible graphene-copper composites via a combined ultrafast laser irradiation and electrodeposition technique

Graphene-metal composites (GMC) possess superior properties, such as high specific strength, and high thermal and electrical conductivity, and have been widely used in many fields. However, the fabrication of GMC still remains to be explored, as existing methods via powder metallurgy and chemical synthesis are difficult to achieve uniform dispersion of graphene, not to mention achieving selective and localized preparation of GMC with complex patterns. In this paper, a simple method for the fabrication of graphene-copper composites (GCC) is firstly proposed by combining flexible laser irradiation and efficient electrodeposition. It not only effectively solves the problems of graphene agglomeration and inhomogeneous dispersion in GCC, but also enables the selective and precise preparation of GCC with spatial micro-patterns. Specifically, an ultrafast picosecond (ps) laser is firstly used to irradiate the polyimide (PI) film to selectively and precisely produce the desired laser-induced graphene (LIG) region. The localized deposition of copper atoms is subsequently made via the electrodeposition step, forming the flexible GCC with a laser-determined spatial pattern. The experimental study of LIG process on PI film has been carried out, and high-quality LIG region is obtained by optimizing the laser scanning path and parameters. On this basis, the regional flexible GCC of 45 μm in thickness with a compact and uniform copper layer of 20 μm has been efficiently fabricated, followed by the detailed characterizations of surface morphology and chemical composition. Furthermore, a significant enhancement of the electrical conductivity has been confirmed, as the measured value is up to 32.8 S/cm at the LIG region and further to about 60.9 S/cm at the GCC area. The mechanical properties of the obtained conductive GCC have been tested and good flexibility is confirmed by nanoindentation and bending tests, verifying its potential for a wide range of applications in flexible electronics, medical and many other fields.

High-performance electroionic artificial muscles boosted by superior ion transport with Ti3C2Tx MXene/Cellulose nanocomposites for advanced 3D-motion actuation

Low-voltage driven electro-ionic soft actuators with large deformation strain are of promising candidate for high-performance artificial muscles, with practical applications in flexible electronics, biomedical assistive devices and soft robotics. However, enhancing the actuation response and long-term stability along with excellent bending properties simultaneously still remain significant challenges. Herein, an elaborate ionically crosslinked nanocomposite membrane, assembled with 1D bacterial cellulous (BC) nanofibers and 2D Ti3C2Tx MXene nanomaterials, is reported to improve constrained ion transport for high-performance electrically activated ionic actuator. The 3D interpenetrating frameworks, arising from the synergistic effects of such combination, not only serve to enhance ion selectivity through the presence of intrinsically negatively charged functional groups but also expand the initially confined pathways, thus diminishing the energy barrier to ion transport. As a result, the integrated superior functionalities of the soft actuator exhibit large bending strain of 0.88 % with the tip displacement of 10.8 mm, ultra-stable cycling performance (>99 % retention for 5 h), and ultrabroad material response range up to 18 Hz under an ultralow voltage exertion of 0.5 V. Furthermore, the demonstration of the prototype soft actuators as actuating tracking beams of 3D-adaptive motion platform for plate deformable mirror shows their potential applications of soft robotics, thereby offering a dependable solution for driving the next generation of sophisticated intelligent systems.

A Real‐Time Process Diagnostic to Support Reliability, Control, and Fundamental Understanding in Aerosol Jet Printing

Aerosol jet printing is a compelling technology for hybrid electronics, combining digital and noncontact patterning with broad materials compatibility, resolution as fine as ≈10 microns, and a high standoff distance of 1–5 mm. Despite its growing popularity in research environments, a robust process understanding and improved manufacturing control are essential for achieving the reliability and predictability required for broader adoption in advanced applications. Herein, recent developments in process monitoring using in‐line light scattering measurements are discussed, including their mechanistic foundations, experimental validation, relevance for process control and reliability, and value as a diagnostic tool for fundamental studies. Experimental measurements confirm the correlation between measured light scattering and deposition rate. Building on this platform, feedback from the real‐time measurement is coupled with printer software to support automated closed‐loop control via a simple proportional‐integral‐derivative software control loop. Combined with the utility of these measurements as a diagnostic to accelerate ink formulation and support fundamental process science experiments, this in‐line measurement provides a useful tool to improve print reliability with the potential to advance the adoption and capabilities of this method in conformal, flexible, and hybrid electronics applications.

Resistive Switching Properties in Copper Oxide–Graphene Oxide Nanocomposite-Based Devices for Flexible Electronic Applications

Resistive Switching Properties in Copper Oxide–Graphene Oxide Nanocomposite-Based Devices for Flexible Electronic Applications

High-Saline-Enabled Hydrophobic Homogeneous Cross-Linking for Extremely Soft, Tough, and Stretchable Conductive Hydrogels as High-Sensitive Strain Sensors.

Design of admirable conductive hydrogels combining robust toughness, soft flexibility, desirable conductivity, and freezing resistance remains daunting challenges for meeting the customized and critical demands of flexible and wearable electronics. Herein, a promising and facile strategy to prepare hydrogels tailored to these anticipated demands is proposed, which is prepared in one step by homogeneous cross-linking of acrylamide using hydrophobic divinylbenzene stabilized by micelles under saturated high-saline solutions. The influence of high-saline environments on the hydrogel topology and mechanical performance is investigated. The high-saline environments suppress the size of hydrophobic cross-linkers in micelles during hydrogel polymerization, which weaken the dynamic hydrophobic associations to soften the hydrogels. Nevertheless, the homogeneous cross-linked networks ensure antifracture during ultralarge deformations. The obtained hydrogels show special mechanical performance combining extremely soft deformability and antifracture features (Young's modulus, 5 kPa; stretchability, 10200%; toughness, 134 kJ m-2; and excellent anticrack propagation). The saturated-saline environments also endow the hydrogels with desirable ion conductivity (106 mS cm-1) and freezing resistance (<20 °C). These comprehensive properties of the obtained hydrogels are quite suitable for flexible electronic applications, which is demonstrated by the high sensitivity and durability of the derived strain sensors.

Subvoxel‐Controlled Microfluidic Printing of Dual‐Material and Multi‐Structural Filaments

Filaments with multi‐materials, complex structures, and sophisticated functions are of great importance to wearable electronics, flexible actuators, and sensors. Direct ink writing (DIW) is mainly adopted to fabricate functional filaments. However, finely regulating the filament's structure is difficult due to the unmovable and static extruding nozzle parts. Here, a dynamically adjustable DIW platform is presented with a movable needle in a Y‐shaped microfluidic nozzle, enabling precise subvoxel control over the structure of the inner layer to print dual‐material and multi‐structure filaments. The position, proportion, and shape of the filaments’ inner layer can be precisely manipulated by adjusting the extruding pressure and the motion of the needle's position in the microfluidic nozzle. Therefore, filaments with various complex structures can be fabricated. Via the printing platform, wavy inner structures are manufactured for stretchable conductance‐stable and triboelectric nanogenerator fibers to realize energy harvesting and self‐powered sensing. Such subvoxel‐controlled microfluidic printing significantly increases the complexity of dual‐material filaments to provide potential applications for flexible electronics.

Highly Flexible Dielectric Films from Solution Processable Covalent Organic Frameworks.

Covalent organic frameworks (COFs) are known to be a promising class of materials for a wide range of applications, yet their poor solution processability limits their utility in many areas. Here we report a pore engineering method using hydrophilic side chains to improve the processability of hydrazone and β-ketoenamine-linked COFs and the production of flexible, crystalline films. Mechanical measurements of the free-standing COF films of COF-PEO-3 (hydrazone-linked) and TFP-PEO-3 (β-ketoenamine-linked), revealed a Young's modulus of 391.7 MPa and 1034.7 MPa, respectively. The solubility and excellent mechanical properties enabled the use of these COFs in dielectric devices. Specifically, the TFP-PEO-3 film-based dielectric capacitors display simultaneously high dielectric constant and breakdown strength, resulting in a discharged energy density of 11.22 J cm-3 . This work offers a general approach for producing solution processable COFs and mechanically flexible COF-based films, which hold great potential for use in energy storage and flexible electronics applications.