Cyclic Bending Research Articles

Design of Ultra‐Narrow Bandgap Polymer Acceptors for High‐Sensitivity Flexible All‐Polymer Short‐Wavelength Infrared Photodetectors

All‐polymer photodetectors possess unique mechanical flexibility and are ideally suitable for the application in next‐generation flexible, wearable short‐wavelength infrared (SWIR, 1000–2700 nm) photodetectors. However, all‐polymer photodetectors commonly suffer from low sensitivity, high noise, and low photoresponse speed in the SWIR region, which significantly diminish their application potential in wearable electronics. Herein, two polymer acceptors with absorption beyond 1000 nm, namely P4TOC‐DCBT and P4TOC‐DCBSe, were designed and synthesized. The two polymers possess rigid structure and good conformational stability, which is beneficial for reducing energetic disorder and suppressing dark current. Owing to the efficient charge generation and ultralow noise current, the P4TOC‐DCBT‐based all‐polymer photodetector achieved a specific detectivity () of over 1012 Jones from 650 (visible) to 1070 nm (SWIR) under zero bias, with a response time of 1.36 μs. These are the best results for reported all‐polymer SWIR photodetectors in photovoltaic mode. More significantly, the all‐polymer blend films exhibit good mechanical durability, and hence the P4TOC‐DCBT‐based flexible all‐polymer photodetectors show a small performance attenuation (<4%) after 2000 cycles of bending to a 3 mm radius. The all‐polymer flexible SWIR organic photodetectors are successfully applied in pulse signal detection, optical communication and image capture.

Experimental investigations on normal mode nodes as support positions of a resonant testing facility for bending fatigue tests

AbstractLarge‐scale fatigue testing is very important to the research on scale effects, which occur in large cyclic loaded structures, such as wind turbine towers. However, such experimental testing has a very high energy consumption. As an efficient alternative, this paper presents a new resonant testing facility for large‐scale specimens under cyclic bending loads. The facility works as a 4‐point bending test, in which the specimen is supported in the nodes of its first normal bending mode, where theoretically no reaction forces occur. Two counter‐rotating imbalance motors with excitation frequencies near resonance generate a harmonic force acting on the specimen. Experimental trial fatigue tests on a steel pipe as a specimen were carried out, in order to validate the new testing setup. A great decrease in the support forces was reached by placing the supports at the normal mode nodes. Additionally, the behavior of the support forces under varying positions and excitation frequencies was also investigated. In summary, the resonant testing method combined with the supports at the normal mode nodes offers an efficient and energy‐saving testing setup for large‐scale fatigue tests.

A highly sensitive and fully flexible Fe-Co metal-organic framework hydrogel based gas sensor for ppb level detection of acetone

Most nanomaterials based gas sensors are established on rigid substrates which require operation at elevated temperature and involve long recovery times, thus, limiting their practical applications. Addressing these issues, we demonstrate a fully flexible Fe/Co metal organic framework hydrogel (Fe/Co MOF HG) based gas sensor that detects ultra-low concentrations of acetone at room temperature. This hydrogel is synthesized using optimized concentration (3:1 M ratio) of Co:Fe with benzene dicarboxylic acid (BDC) in Fe/Co MOF via solvothermal method followed by lyophilization. Detailed morphological evaluation reveals 3-dimentional porous structure with multiple voids which largely enhances the specific surface area. Upon exposure to acetone, the Fe/Co MOF HG with Cu metal contacts based sensor exhibits a sensing response (S%) of 12.28 % to 500 ppb of acetone with a wide dynamic range of 200 ppb to 4 ppm. This remarkable sensitivity can be attributed to the abundance of water-adsorbed oxygen (Oc% = 24.58 %) in hydrogel as confirmed by XPS technique, which helps in the increase of the adsorption of a large proportion of acetone molecules on the surface of hydrogel. The limit of detection (LOD = 3σ/s) is found to be 103 ppb which is significantly lower than the other reported MOF-based acetone sensors. Further, the sensor demonstrates excellent selectivity against other common VOCs such as ammonia, benzene, toluene, and formaldehyde. Finally, the sensor’s outstanding stability (upto one-month), mechanical robustness when subjected to 230 cycles of bending and resilience to changes in humidity opens up new possibilities for the use of MOF-based hydrogels as gas sensors in several wearable device domains, such as health care and environmental monitoring.

Nacre-inspired hierarchical bionic substrate for enhanced thermal and mechanical stability in flexible applications

Flexible substrates, essential for flexible electronics by providing support and flexibility while influencing sensor stability, still face challenges in achieving mechanical and thermal stability, particularly in large-scale production and cost control. Inspired by the nacre's “brick-and-mortar” hierarchical microstructure, this study introduces PPSN (paper/polydimethylsiloxane (PDMS)/Si₃N₄ nanoparticles), a novel flexible substrate that mimics the “brick-and-mortar” structure. PPSN, with its topological interlocking and assembly technique, provides excellent thermal and mechanical stability, including high-temperature resistance and stress dissipation. An optimized Si₃N₄ content of 1.0 wt% yields a peak elastic modulus of 1245.27 MPa while maintaining hydrophobicity, with a contact angle of 127.1° at 3.0 wt%. The substrate shows excellent fatigue durability, retaining its morphology after 10,000 bending cycles. Thermal analysis indicates a stable CTE below 20 ppm/°C up to 300°C, rising to 200 ppm/°C between 350 and 400°C. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveal minimal thermal decomposition with mass loss below 0.5 % from 25 to 300°C and under 3 % at 400°C. Additionally, electrodes were printed on the substrate using screen printing and ion beam deposition (IBD), demonstrating good material adhesion. A flexible temperature sensor was fabricated and exhibited good sensitivity and stability with a TCR of −0.262 % °C⁻¹. PPSN advances traditional materials with superior mechanical strength, thermal stability, and durability, offering significant scientific and practical value for flexible electronics and low-cost biomimetic processes.

Room-Temperature, Solution-Processed, Robust, Transparent, and Conductive SiOx/AgNW Nanocomposite Coating.

AgNW networks show high promise as a conductive material due to excellent flexibility, low resistance, high transparency, and ease of large-scale preparation. However, the application of AgNW networks has been hindered by their inherent characteristics, such as easy oxidation degradation, chemical corrosion, and structural instability at high temperatures. In this study, a dense SiOx protective layer derived from perhydropolysilazane was introduced to fabricate a robust SiOx/AgNW nanocomposite coating through an all-solution process at room temperature. The achieved nanocomposite coating shows outstanding thermal stability up to 450 °C, resistance to ultraviolet radiation, and excellent mechanical performance by maintaining stability after 10,000 cycles of bending at a radius of 2.5 mm, 1000 cycles of peeling, and 1200 cycles of wearing. Meanwhile, the nanocomposite coating demonstrates exceptional chemical tolerance against HCl, Na2S, and organic solvents. A transparent heater based on the nanocomposite coating achieves a remarkable benchmark with a maximum temperature of 400 °C at 20 V. These features highlight the potential of the nanocomposite coating in flexible electronics, optoelectronics, touch screens, and high-performance heaters.

Remote vapor-phase dual alkali halide salts assisted quasi-van der Waals epitaxy of m-phase ZrO2 thin films with high dielectric constant and stable flexible properties

High-κ dielectric constant and wideband gap of ZrO2 material render it as an excellent candidate for transistor gate dielectric layers. However, current reported synthesis techniques suffer the problems of high precursor volatilization rate, ultrasmall grains with low dielectric constant, and high leakage current, which largely impede its application in electronic devices. Here, the quasi-van der Waals epitaxy growth of compact m-phase ZrO2 thin films has been developed, in which the stable supply of Zr source is realized by the tuned sublimation of ZrC powder with remote vapor-phase dual halide salts assistant. The formation of m-phase ZrO2 is due to the lower Gibbs free energy, in which the crystal nucleates at the etched hole edges of mica substrate, thus forming hexagonal shape polycrystal grains and merging as the continuous thin films. The microstructures and Raman spectrum characterization reveal the two dominated growth orientations and good crystal qualities, which indicate the uniform dielectric constant. The excellent growth reproducibility could be easily adapted to thin metal substrates, such as tungsten, molybdenum, and stainless steel, where the adhesion strength is strong because of the higher density of interfacial chemical bonding. Meanwhile, the metal–insulator–metal flexible capacitors show the high dielectric constant of 23–26 and low leakage current density of 10−4 A/cm2 at large voltage and only exhibit the decreased capacitance density of 7% after several hundred bending cycles. Our work paves a way to achieve the high-quality dielectric thin films on various substrates by the unique chemical vapor deposition design strategy.

Flexible Transparent Films of Oriented Silver Nanowires for a Stretchable Strain Sensor.

The potential applications of stretchable strain sensors in wearable electronics have garnered significant attention. However, developing susceptible stretchable strain sensors for practical applications still poses a considerable challenge. The present study introduces a stretchable strain sensor that utilizes silver nanowires (AgNWs) embedded into a polydimethylsiloxane (PDMS) substrate. The AgNWs have high flexibility and electrical conductivity. A stretchable AgNW/Pat-PDMS conductive film was prepared by arranging nanowires on the surface of PDMS using a simple rod coating method. Depending on the orientation angle, the overlap area between nanowires varies, resulting in different levels of separation under a given strain. Due to the separation of the nanowire and the change in current path geometry, the variation in strain resistance of the sensor can be primarily attributed to these factors. Therefore, precision in strain regulation can be adjusted by altering the angle θ (0°, 60°, or 90°) of the nanowire. At the same time, the stability of the AgNW/Pattern-PDMS (AgNW/Pat-PDMS) conductive film application was verified by preparing a sandwich structure PDMS/AgNW/Pat-PDMS stretchable strain sensor. The sensor exhibited high sensitivity within the operating sensing range (gauge factor (GF) of 15 within ~120% strain), superior durability (20,000 bending cycles and 5000 stretching cycles), and excellent response toward bending.

Biscrolled hierarchical hybrid structure of PEDOT:PSS/CNTs-NMP yarn based solid state linear supercapacitor for wearable e-textile

The environmental friendly flexible solid state linear supercapacitor (FSLSc) based on the hierarchical hybrid yarn with core-shell type structure of poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) and hydrophilic carbon nanotubes (CNTs) sheet, fabricated using novel biscrolling technique is proposed. The hierarchical hybrid yarn structure of the electrode establishes the improved electrochemical interface of PEDOT:PSS with the both the hydrophilic CNTs and an aqueous PVA/H3PO4 gel electrolyte. The exterior surface of the yarn electrode rich in PEDOT:PSS which interact with ions from electrolyte and stores charges faradaically while the core region with dense CNTs yarn contributes with its multifunctional capabilities such as EDLC type capacitor, current collector and mechanical support. The observed two-fold decrease in ESR value (∼49Ω) and two-fold increase in capacitance (∼112.76 F/g) for hybrid yarn electrode with N-methyl-2-pyrrolidone (NMP) treated hydrophilic CNTs compared to the one with pristine CNTs, confirms the improved interface of PEDOT:PSS formed with hydrophilic CNTs and aqueous electrolyte. The FSLSc devices with NMP treated CNTs hybrid yarn electrodes exhibited excellent electrochemical performance in terms of the maximum power and energy density of 980 W/kg and 3.799 Wh/kg, respectively. The FSLSc displayed remarkable cycling performance upto 5000 cycles of charge-discharge and a robust bending stability after 1000 bending cycles, making it promising for practical application of the next-generation flexible solid state electrochemical energy storage in e-textiles.

Ni3C nanosheets and PVA nanocomposite based memristor for low-cost and flexible non-volatile memory devices

Two-dimensional (2D) MXenes have gained extensive attention in the field of memristors due to their high ion mobility, chemical stability and tunable electrical and surface properties. Moreover, MXenes have tunable interlayer bonding which enables enhancement in memristor performance. In this work, we synthesize a novel nanocomposite of Ni3C nanosheets and polyvinyl alcohol (PVA) and fabricate a flexible memristor with Ag/Ni3C-PVA/ITO/PET configuration for non-volatile memory applications. Ni3C nanosheets were synthesized from Ni-MAX (Ni3AlC2) through a solvothermal etching and exfoliation process. The nanosheet like structure of Ni3C is confirmed through Scanning Electron Microscopy (SEM) and Transmission Electron microscopy (TEM). Characterization techniques like X-ray diffraction (XRD), Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) reveal the crystalline phases, surface functional groups and chemical bonds present in Ni3C nanosheets and Ni3C-PVA nanocomposite. The memristor was fabricated through a facile low cost solution processed based fabrication technique. The Ag/Ni3C-PVA/ITO/PET memristor exhibits bipolar non-volatile switching characteristics. The device with optimised mass ratio of 4:3 (Ni3C: PVA) shows a decent off/on ratio of 2.09 × 102, long retention time of 104 s, and an endurance of 102 DC cycles. The SET voltage of the as-fabricated device is 2.8 V and the RESET voltage is −5.33 V. The flexible memristor exhibits outstanding mechanical robustness over 500 bending cycles. The high charge carrier mobility of Ni3C results in lower switching voltage and the dielectric property of PVA improves data retention and off/on ratio of the memristor. The resistive switching behaviour is explained through conductive metallic bridge mechanism. The conduction mechanism follows Ohmic conduction in ON state and trap controlled space charge limited current (TCSCLC) mechanism in OFF state. The results demonstrate that the nanocomposite with its superior resistive switching effects is suitable for cost-effective, high-performance, flexible non-volatile memory devices.

Flexible Acetylcholine Neural Probe with a Hydrophobic Laser-Induced Graphene Electrode and a Fluorous-Phase Sensing Membrane.

This work develops the first laser-induced graphene (LIG)-based electrochemical sensor with a superhydrophobic fluorous membrane for a flexible acetylcholine (ACh) sensor. ACh regulates several physiological functions, including synaptic transmission and glandular secretion. The ACh sensing membrane is doped with a fluorophilic cation-exchanger that can selectively measure ACh based on the inherent selectivity of the fluorous phase for hydrophobic ions, such as ACh. The fluorous-phase sensor improves the selectivity for ACh over Na+ and K+ by 2 orders of magnitude (compared to traditional lipophilic membranes), thus lowering the detection limit in artificial cerebrospinal fluid (aCSF) from 331 to 0.38 μ M, thereby allowing measurement in physiologically relevant ranges of ACh. Engraving LIG under argon creates a hydrophobic surface with a 133.7° contact angle, which minimizes the formation of a water layer. The flexible solid-contact LIG fluorous sensor exhibited a slope of 59.3 mV/decade in aCSF and retained function after 20 bending cycles, thereby paving the way for studying ACh's role in memory and neurodegenerative diseases.

Fabrication of flexible pressure sensor for human detection by direct-write printing concave surface

Flexible pressure sensor plays an important role in the field of human-computer interaction area due to its high flexibility and sensitivity. Convex surface of flexible electrodes provide an efficient way to enhance the sensitivity of flexible pressure sensors. However, facilely preparing controllable convex surface of flexible electrodes is still a challenge for obtaining high sensitive flexible pressure sensors. In this paper, direct-write print technique was utilized to prepare a concave structure surface with viscoelastic substrate, which could be used to prepare convex structure flexible electrode for fabricating highly sensitive flexible pressure sensors. Interaction between ink droplet and substrate was explored to generate a concave template, which could be controlled in spacing and diameter with printing spacing and nozzle diameter. Convex structure flexible surface could be prepared with the concave template, and then the convex structure flexible electrode could be realized with the evaporation of metallic silver on the surface. Furthermore, flexible pressure sensor was assembled with an interlocking structure by stacking two convex structure flexible electrodes in a face-to-face way, which could efficiently enhance flexibility and electrical property. The flexible pressure sensor presents a high sensitivity, a fast response/recovery time (<100 ms) and excellent flexibility (more than 10,000 cycles of bending), which could be applied in monitor physiological signals such as pulse detection, sound vibration, finger bending and so on. Therefore, this work provides an efficient method for preparing controllable structured surface, which has a great potential in the fabrication of flexible sensors, wearable electronics and energy devices.

Continuous fabrication of flexible, high-performance PEDOT: PSS thermoelectric fiber without post-processing

Organic thermoelectric fibers (OTEFs) are popular in wearable self-powered technology due to easy weaving and power generation. However, limitations include poor spinning capability, weak mechanical strength, low output power, and dangerous post-treatment. Here, we report the rapid preparation of flexible, high-performance OTEFs without post-treatment through introducing ionic liquid (IL) of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMIM: TFSI) into the Poly (3,4-ethylene dioxythiophene): Poly (styrene sulfonate) (PEDOT: PSS) to enhance thermoelectric properties, and mechanical strength, with just 1 wt% of IL enabling continuous fabrication of the PEDOT: PSS fiber. The resulting fiber exhibits remarkable electrical, and thermoelectric performance of ∼2267.7 S cm−1, and ∼85 μW m−1 K−2, respectively. It also demonstrates excellent strength (∼289.72 MPa), with a resistance change of less than 8 % after 10,000 bending cycles. The fabricated five-legs devices achieve an impressive output power and output power density of ∼7.84 nW and ∼4.32 μW cm−2 at 49 K, and the fabric textile generates a significant voltage of ∼47.8 mV using human body heat. This work proposes a new design strategy for high-performance organic thermoelectric fibers without additional post-processing, and the ultra-high output power and flexibility exhibit excellent combined application potential in both organic and inorganic TE fields.

Highly Stable Flexible Organic Electrochemical Transistors with Natural Rubber Latex Additives.

Organic electrochemical transistors (OECTs) have attracted considerable interest in the context of wearable and implantable biosensors due to their remarkable signal amplification combined with seamless integration into biological systems. These properties underlie OECTs' potential utility across a range of bioelectronic applications. One of the main challenges to their practical applications is the mechanical limitation of PEDOT:PSS, the most typical conductive polymer used as a channel layer, when the OECTs are applied to implantable and stretchable bioelectronics. In this work, we address this critical issue by employing natural rubber latex (NRL) as an additive in PEDOT:PSS to improve flexibility and stretchability of the OECT channels. Although the inclusion of NRL leads to a decrease in transconductance, mainly due to a reduced carrier mobility from 0.3 to 0.1 cm2/V·s, the OECTs maintain satisfactory transconductance, exceeding 5 mS. Furthermore, it is demonstrated that the OECTs exhibit excellent mechanical stability while maintaining their performance even after 100 repetitive bending cycles. This work, therefore, suggests that the NRL/PEDOT:PSS composite film can be deployed for wearable/implantable applications, where high mechanical stability is needed. This finding opens up new avenues for practical use of OECTs in more robust and versatile wearable and implantable biosensors.

Planar Micro-Supercapacitors with High Power Density Screen-Printed by Aqueous Graphene Conductive Ink.

Simple and scalable production of micro-supercapacitors (MSCs) is crucial to address the energy requirements of miniature electronics. Although significant advancements have been achieved in fabricating MSCs through solution-based printing techniques, the realization of high-performance MSCs remains a challenge. In this paper, graphene-based MSCs with a high power density were prepared through screen printing of aqueous conductive inks with appropriate rheological properties. High electrical conductivity (2.04 × 104 S∙m-1) and low equivalent series resistance (46.7 Ω) benefiting from the dense conductive network consisting of the mesoporous structure formed by graphene with carbon black dispersed as linkers, as well as the narrow finger width and interspace (200 µm) originating from the excellent printability, prompted the fully printed MSCs to deliver high capacitance (9.15 mF∙cm-2), energy density (1.30 µWh∙cm-2) and ultrahigh power density (89.9 mW∙cm-2). Notably, the resulting MSCs can effectively operate at scan rates up to 200 V∙s-1, which surpasses conventional supercapacitors by two orders of magnitude. In addition, the MSCs demonstrate excellent cycling stability (91.6% capacity retention and ~100% Coulombic efficiency after 10,000 cycles) and extraordinary mechanical properties (92.2% capacity retention after 5000 bending cycles), indicating their broad application prospects in flexible wearable/portable electronic systems.

An ultrathin, rapidly fabricated, flexible giant magnetoresistive electronic skin

In recent years, there has been a significant increase in the prevalence of electronic wearables, among which flexible magnetoelectronic skin has emerged as a key component. This technology is part of the rapidly progressing field of flexible wearable electronics, which has facilitated a new human perceptual development known as the magnetic sense. However, the magnetoelectronic skin is limited due to its low sensitivity and substantial field limitations as a wearable electronic device for sensing minor magnetic fields. Additionally, achieving efficient and non-destructive delamination in flexible magnetic sensors remains a significant challenge, hindering their development. In this study, we demonstrate a novel magnetoelectronic touchless interactive device that utilizes a flexible giant magnetoresistive sensor array. The flexible magnetic sensor array was developed through an electrochemical delamination process, and the resultant ultra-thin flexible electronic system possessed both ultra-thin and non-destructive characteristics. The flexible magnetic sensor is capable of achieving a bending angle of up to 90 degrees, maintaining its performance integrity even after multiple repetitive bending cycles. Our study also provides demonstrations of non-contact interaction and pressure sensing. This research is anticipated to significantly contribute to the advancement of high-performance flexible magnetic sensors and catalyze the development of more sophisticated magnetic electronic skins.

A Flexible and High-Efficient Anti-Icing/Deicing Coating Based on Carbon Nanomaterials.

Anti-icing/deicing coatings with low energy consumption and superior flexibility could better fit application requirements in practical engineering. In this paper, an active-passive-integrated anti-icing/deicing coating based on carbon nanomaterials is prepared, which not only possesses various functions of electrothermal conversion, photothermal conversion, and superhydrophobicity but also shows a large deformability to accommodate curved surfaces. The coating consists of a sandwich-structured bottom part and top layer, the former of which includes a core conductive layer made of densely mixed carbon nanotubes (CNTs) and graphene and two polydimethylsiloxane (PDMS) wrapping layers, while the latter is a polymeric composite filled with TiN and SiO2 nanoparticles. Experimental studies show that, when the present coating works under an electric field alone, a 90% conversion of electric energy to thermal energy can be realized, only a 2 V voltage is enough to unfreeze the surface at minus 20 degrees within 400 s, and a slightly larger voltage of 2.5 V leads to a significant temperature increase of more than 100 °C within 200 s. Such required voltages are significantly smaller than their counterparts in existing electrothermal-based methods to achieve the same heating effects, which could be further diminished with the auxiliary action of sunlight illumination. A fast and complete deicing/defrosting can be consequently achieved with a small energy input. Furthermore, the water repellency function, electric property, and electrothermal conversion performance of the coating remain almost unchanged after either a large bending deformation or many bending cycles, thus ensuring an outstanding anti-icing/deicing effect on both flat and curved surfaces. All of the results demonstrate apparent advantages of the present coating including high efficiency, low energy consumption, all-weather adaptability, and excellent flexibility, which should be of great practical value for the freeze protection of differently shaped industrial equipment.

Enhanced Synaptic Characteristics Under Applied Magnetic Field in V2O5/NiMnIn Based Switching Device for Neuromorphic Computing

The present study reports a memory structure Al/V2O5/NiMnIn on a flexible stainless-steel (SS) substrate for neuromorphic applications. The fabricated device exhibits gradual SET and RESET switching characteristics with an OFF/ON resistance ratio of ~100, good consistency of 4500, and excellent data retention capability up to 3000 s. The current-voltage (I-V) study supports an Ohmic conduction mechanism in the low resistance state (LRS). In contrast, the trap-controlled modified space charge conduction mechanism demonstrated the high resistance state (HRS). The resistance versus temperature measurement (R-T) in the LRS and HRS of the device signifies that oxygen vacancies form the conduction filament. We further analyze the synaptic functioning by applying identical consecutive voltage pulses, and the device's conductance change has been observed. These characteristics show a good representation of the biological memory synapse in terms of the artificial memory device. Long-term potentiation (LTP) and long-term depression (LTD) show nonlinear and asymmetery behavior, which is substantial for neuromorphic applications. A considerable shift in LTP and LTD was detected by applying external temperature and magnetic field. This is explained via temperature and magnetic field strain in the functional NiMnIn bottom electrode of the fabricated device. The mechanical flexibility of the memory structure was tested by exploring the switching characteristics with various bending angles and bending cycles. Therefore, the present study offers new avenues for flexible devices with high data storage capability for futuristic neuromorphic applications.

3D-Printed Hydrogel-Based Flexible Electrochromic Device for Wearable Displays.

Flexible electrochromic devices (FECDs) are widely explored for diverse applications including wearable electronics, camouflage, and smart windows. However, the manufacturing process of patterned FECDs remains complex, costly, and non-customizable. To address this challenge, a strategy is proposed to prepare integrated FECDs via multi-material direct writing 3D printing. By designing novel viologen/polyvinyl alcohol (PVA) hydrogel inks and systematically evaluating the printability of various inks, seamless interface integration can be achieved, enabling streamlined manufacturing of patterned FECDs with continuous production capabilities. The resultant 3D-printed FECDs exhibit excellent electrochromic and mechanical properties, including high optical contrast (up to 54% at 360nm), nice cycling stability (less than 5% electroactivity reduction after 10000 s), and mechanical stability (less than 19% optimal contrast decrease after 5000 cycles of bending). The potential applications of these 3D-printed hydrogel-based FECDs are further demonstrated in wearable electronics, camouflage, and smart windows.

Camphor-Based CVD Graphene Integrating CsPbBr3 Quantum Dots for High-Temperature Endurance, High Flexibility, and Fast Optical Switch Photodetection

Photodetectors (PDs) based on camphor-based CVD graphene integrating CsPbBr3 quantum dots (QDs) have been fabricated on mica substrates successfully, showing temperature resistant, foldable, and fast response properties. The graphene synthesized from eco-friendly camphor was transferred onto mica substrates, and then the CsPbBr3 QDs were coated onto the graphene surface to form CsPbBr3 QDs/graphene composition on a flexible mica substrate. According to the Raman spectrum, the structure of camphor-based CVD graphene is multilayer. The photoresponse of CsPbBr3 QDs/graphene composition was revealed by temperature-dependent (ranging from 300 K to 523 K) I-V measurements with/without white light illumination (light intensity: 112 mW/cm2). To highlight the temperature resistance of PDs based on CsPbBr3 QDs/graphene composition, a photo-to-dark current ratio (PDCR) of at 5 V is estimated at different temperatures. The PDCR of the CsPbBr3 QDs/graphene composition-based PD decreased from 3.2 to 0.74 with increasing temperature from 300 K to 523 K. Moreover, after 0 to 300 bending cycles, the vibration of PDCR value at 5 V is small (from 4.3 to 3.7), showing the high flexibility of the CsPbBr3 QDs/graphene composition-based PD. Furthermore, we found that the rise and fall times of the CsPbBr3 QDs/graphene composition-based PDs when we switched the illumination source ON and OFF are ~ 2 and ~1 ms, respectively, indicating fast optical switch behavior. In this study, camphor-based CVD graphene incorporating CsPbBr3 QDs composition-based PD is demonstrated to exhibit high-temperature resistance, high flexibility, and fast response photodetection.Keywords: Camphor, graphene, CsPbBr3 quantum dots, flexible photodetectors

Flexo-Phototronic Boosted Self-Powered Ultraviolet Detection in ZnAl:Layered Double Hydroxide Nanosheets/NiO Heterostructure.

Developing self-powered and flexible optoelectronic sensors with high responsivity and speed is crucial for modern applications, motivating continuous efforts to enhance their performance. Flexo-phototronics is a less-explored but promising technique to elevate the performance of optoelectronics. Therefore, this work addresses the potential of utilizing the flexo-phototronic effect to enhance the performance of a flexible and self-powered ultraviolet photodetector (UV PD) based on ZnAl:LDH (layered double hydroxides) nanosheets (Ns)/NiO heterostructure. The vertically oriented ZnAl:LDH Ns are synthesized via a simple method involving the immersion of a sputtered 10% Al-doped ZnO thin film in deionized water at room ambient conditions. The fabricated PD exhibits an impressive response to 365 nm UV light, with high sensitivity in the order of 103. The device's photocurrent and responsivity are significantly enhanced by the flexo-phototronic effect, attributed to the flexoelectric properties of ZnAl:LDH Ns. Specifically, applying an inhomogeneous tensile strain of 2% boosted the device responsivity by 57.1% and improved its operational speed. Furthermore, a working model revealing the altered energy-band structure is demonstrated to elucidate the flexo-phototronic-induced boost in the photoresponse. The PD also demonstrated a sustainable performance under severe bending cycles, underlining the good flexibility of the device. The results presented in this study demonstrate a self-powered and flexible UV PD and provide a viable approach to augment the performance of optoelectronics through the flexo-phototronic effect.