AgNW Networks Research Articles

A wearable cotton fiber-based supercapacitor electrode material with outstanding stability and photothermal performance utilizing AgNWs, NiCoAl-LDH, and PPy-NWs

Designing cotton fiber (CF) based flexible electrode materials with both electrochemical energy storage and structural stability is crucial for the utilization of flexible supercapacitors in wearable devices. Nevertheless, the electrochemical properties of such materials are often constrained by suboptimal ion diffusion, a limited electroactive surface area, and inadequate structural integrity. Herein, Silver nanowires (AgNWs), NiCoAl hydrotalcite (NCA-LDH), and polypyrrole nanowires (PPy-NWs) are employed to construct a CF-based electrode material (PNHAS/CF) with high stability through a layer-by-layer self-assembly method. The PNHAS/CF with a high capacitance of 1207.58 mF cm−2 at 5 mA cm−2 due to the faster electronic transmission paths of AgNWs and PPy-NWs, and the high specific capacitance of NCA-LDHs. The NCA-LDH stabilizes the PPy-NWs molecular chain, and the PPy-NWs winding structure can further enhance the PNHAS/CF's structural stability and prevent the AgNWs network from being destroyed, which guarantees the exceptional 87.5 % capacitance retention after 2000 cycles. The constructed symmetrical supercapacitor shows an energy density of 36.28 μWh cm−2 at 0.31 mW cm−2 power density. The PNHAS/CF exhibits superb solar spectral absorptivity (~94.8 %) and outstanding solar heating performance. Surprisingly, the fiber-based flexible electrode material and the assembled supercapacitor are expected to find applications in wearable intelligent electronics.

Flexible AgNW/PDMS nanocomposite for strain and pressure sensing

This study presents the fabrication and characterization of an ultra-thin (<1 mm) piezoresistive sensor based on a silver nanowire (AgNW) and polydimethylsiloxane (PDMS) nanocomposite, capable of simultaneous strain and pressure sensing. The sensor exhibits high sensitivity, detecting strains as low as 0.5 % with a range of up to 40 %, demonstrates frequency responsiveness from 0.5 to 3 Hz, and maintains functionality over 1000 cycles. The sensor’s performance was evaluated through cyclic tensile and compressive tests. We hypothesize that the compression sensing mechanism is a consequence of the Poisson effect in the PDMS substrate, where transverse compression induces axial strains parallel to the AgNW network, causing disconnections within the nanowire matrix. The sensor’s versatility was demonstrated through various biofeedback applications, including finger bending, applied pressure, calf raises, and elbow flexion. With its thin profile and dual-mode sensing capability, this AgNW/PDMS nanocomposite sensor shows promise for biomechanics, sports science, and healthcare monitoring applications.

Hydrogen Evolution Activity of Platinum Nanoparticles Decorated on Silver Nanowire Networks and Graphite Electrodes

The catalytic activity of graphite (C) and conductive silver nanowire (AgNW) networks coated on glass and graphite substrates with low platinum content towards hydrogen evolution reaction (HER) is reported. The results exhibit that the chronoamperometric electrodeposition of platinum on AgNW substrates results in the formation of spherically shaped nanoparticle agglomerates aligned on the nanowires. Also, platinum doped graphite electrodes with a rough surface showed an efficient distribution of platinum nanoparticles (PtNPs). Studies of the electrocatalytic HER activity as a function of platinum loading indicate that the optimum loading is in the range of 60 µg/cm2 and further loading results only in a minor reduction of the overpotential. At low Pt content, a synergistic effect of the AgNW network in terms of enhancement of the HER performance was observed. Tafel analysis showed that in the low overpotential region, the Volmer reaction was the rate determining step for the graphite based electrodes. The graphite substrate in conductive connection with the nanowires was shown to significantly boost the hydrogen formation rate.

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.

Improved preparation of AgNW film and its application in flexible counter electrodes of dye-sensitized and perovskite solar cells

Silver nanowire (AgNW) has been wildly used to prepare flexible conducting substrate of electronic and optoelectronic devices. By coating a layer of carbon onto a polymer/AgNW substrate, a counter electrode (CE) was obtained and it offers the advantages of high flexibility, light weight, low cost, simple fabrication, and operating efficiently in dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). By modifying the traditional unidirectional roll-coating process of AgNW to cross-directional coating, the morphology and distribution of the AgNW network was improved, which led to increased transmittance and electroconductivity, and subsequently improved cell efficiency of DSSCs and PSCs. The performance of the CEs and solar cells was further promoted by optimized fabrication process of the carbon layer. The as-prepared flexible CEs achieved great enhancement of cell efficiencies, and maximum power conversion efficiencies of 5.17% and 14.32% were obtained by DSSCs and PSCs, respectively.

Capillary Force-Induced Graphene Spontaneous Transfer and Encapsulation of Silver Nanowires for Highly-Stable Transparent Electrodes.

Silver nanowires (NWs) (AgNWs) have emerged as the most promising conductive materials in flexible optoelectronic devices owing to their excellent photoelectric properties and mechanical flexibility. It is widely acknowledged that the practical application of AgNW networks faces challenges, such as high surface roughness, poor substrate adhesion, and limited stability. Encapsulating AgNW networks with graphene has been recognized as a viable strategy to tackle these issues. However, conventional methods like self-assembly reduction-oxidation or chemical vapor deposition often yield graphene protective layers with inherent defects. Here, we propose a novel one-step hot-pressing method containing ethanol solution that combines the spontaneous transfer and encapsulation process of rGO films onto the surface of the AgNWs network, enabling the preparation of flexible rGO/AgNWs/PET (reduced graphene oxide/silver NWs/polyethylene terephthalate) electrodes. The composite electrode exhibits outstanding photoelectric properties (T ≈ 88%, R ≈ 6 Ω sq-1) and possesses a smooth surface, primarily attributed to the capillary force generated by ethanol evaporation, ensuring the integrity of the rGO delamination process on the original substrate. The capillary force simultaneously promotes the tight encapsulation of rGO and AgNWs, as well as the welding of the AgNWs junction, thereby enhancing the mechanical stability (20,000 bending cycles and 100 cycles of taping tests), thermal stability (∼30 °C and ∼25% humidity for 150 days), and environmental adaptability (100 days of chemical attack) of the electrode. The electrode's practical feasibility has been validated by its exceptional flexibility and cycle stability (95 and 98% retention after 5000 bending cycles and 12,000 s long-term cycles) in flexible electrochromic devices.

Solvent Vapor Annealing and Plasma Treatment Stabilize Silver Nanowire Layers

AbstractSilver nanowires (AgNW) find use in transparent conductive electrodes with applications in solar cells, touch screens, and wearables. Unprotected AgNW are prone to atmospheric corrosion and lose conductivity over time. Known passivation techniques either require submersion of pre‐deposited AgNW in liquid compounds or the modification of AgNW inks prior to deposition, which alters viscosity and complicates deposition. Here, new possibilities for stabilization of pre‐deposited AgNW networks without need for submersion are explored. It is demonstrated that AgNW networks can be stabilized either by argon or hydrogen plasma treatment or by solvent vapor annealing with ethanol, methanol, or ethyl acetate. These treatments yielded stable electrical resistance over at least nine weeks, whereas untreated or thermally annealed AgNW layers quickly lost conductivity. The potential of solvent vapor annealing is further explored by demonstrating a new processing technique for stable polymer matrix composites containing AgNW. Co‐deposited layers of AgNW with polystyrene microbeads are annealed in ethyl acetate vapor to stabilize the AgNW while at the same time merging polymer beads into a closed film around the AgNW. The resulting composites maintained stable resistance and transmittance for at least seven weeks.

Wrinkled TiNAgNW Nanocomposites for High-Performance Flexible Electrodes on TEMPO-Oxidized Nanocellulose.

In this study, we present a novel method for fabricating semi-transparent electrodes by combining silver nanowires (AgNW) with titanium nitride (TiN) layers, resulting in conductive nanocomposite coatings with exceptional electromechanical properties. These nanocomposites were deposited on cellulose nanopaper (CNP) using a plasma-enhanced pulsed laser deposition (PE-PLD) technique at low temperatures (below 200 °C). Repetitive bending tests demonstrate that incorporating AgNW into TiN coatings significantly enhances the microstructure, increasing the electrode's electromechanical robustness by up to four orders of magnitude compared to commercial PET/ITO substrates. Furthermore, the optical and electrical conductivities can be optimized by adjusting the AgNW network density and TiN synthesis temperature. Our results also indicate that the nanocomposite electrodes exhibit improved stability in air and superior adhesion compared to bare AgNW coatings.

Post-treatment optimization for silver nanowire networks in transparent droplet-based TENG sensors

Transparent conducting electrodes (TCEs) serve as essential components in various devices, including smart windows, thin film heaters, and sensors. Historically, indium tin oxide (ITO) thin films have served as the primary TCE material. However, the scarcity of indium in the Earth’s crust and costly vacuum-based deposition processes have prompted researchers to seek alternatives. While silver nanowire (Ag NW) networks have emerged as the leading candidate for TCEs among various alternatives, the presence of polyvinyl pyrrolidone (PVP) layer surrounding Ag NWs often leads to substantial contact resistances at the junction areas. Given the diverse characteristics of Ag NWs, including length, diameter, PVP thickness, and deposition methods, the efficacy of a specific post-treatment method on the same Ag NW batch remained unknown. This work collected effective post-treatment methods from existing literature and innovatively developed in-house approaches to optimize the treatment of Ag NW networks. Following post-treatment, the resulting electrodes exhibited a 70 % reduction in sheet resistance, with only a marginal 1 % decrease in optical transmittance. The optical figure of merit (FoM) for the optimized networks showed a remarkable five-fold improvement, rising from 66 to 305. The optimized Ag NW networks were then utilized as current collectors in water droplet-based TENG sensors, showcasing the device's effectiveness in pH and chemical concentration sensing. The fabricated TENG recorded peak Voc and Isc values of 22 V and 370 nA, respectively. Furthermore, we developed a sensor-integrated device capable of gauging the incident droplets’ pH level, signaling acid rain safety. In addition, the droplets activate a large-area Ag NW-based transparent thin film heater. Rapid defogging and defrosting capabilities of the heater was also demonstrated. The device holds the potential to be applied to the side-view mirrors of cars, providing an anti-fogging display for a significantly safer journey.

Silver Nanowire Reinforced Conductive and Injectable Colloidal Gel for Effective Wound Healing Via Electrical Stimulation.

The remarkable biocapacity, injectability, and adaptability of colloidal gels lead to their widespread use in tissue engineering as irregular defect implants. However, multifunctionalities including electroconductivity and antibacterial property are highly required for colloidal gels. In addition, the inherently weak mechanical property of physically crosslinked colloidal gels limits their application. Herein, Ag nanowires (Ag NWs)-reinforced colloidal gels composed of biocompatible gelatin nanoparticles and polydopamine-modified Ag NWs through the controlled electrostatic assembly, which are injectable and conductive, are presented. 1D Ag NWs can significantly improve the mechanical and electrical properties of the colloidal gel while maintaining its inherent excellent injectability. Owing to the network of Ag NWs, the storage modulus and conductivity of the optimized Ag NW colloidal gel are 7.5 and 13 times higher, respectively, than those of the colloidal gel made up of polydopamine-modified Ag nanoparticles with equivalent Ag concentration. Further, this Ag NW colloidal gel can adapt to sharp wounds on skin, which accelerates the healing of an MRSA-infected wound via electrical stimulation.

Evaporation-induced self-assembled ultrathin AgNW networks for highly conformable wearable electronics

The flexibility and stability of transparent electrodes play a crucial role in the growing popularity of flexible devices, especially in potential wearable electronics. To date, various solution-coating techniques have been developed for fabricating silver nanowire (AgNW) flexible bioelectronics. However, achieving the orderly distributed patterns of AgNW without undesirable aggregations still poses a grand challenge. Here, an approach to realize regular patterned ultrathin AgNW networks on a freestanding electrospun PVDF-TrFE frame by evaporation-induced self-assembly is proposed. The patterning mechanism of evaporating AgNW colloidal suspension is investigated from experimental and theoretical analysis. The influence of evaporation-induced flow inside colloidal freestanding membranes on forming regular square hole-shaped arrays, selective deposition of AgNW, and aligning them along the artificial pinning array are addressed. Owing to the orderly arrangement of AgNW networks, the resultant flexible electrode achieves ultrathin thickness (about 5 μm), high optical transmittance (87.8%), and low sheet resistance (8.4 Ω·sq−1) with a relatively low dosage of AgNW (9 μg·cm−2). The electrode exhibits excellent durability during cyclic bending (50,000 times) and stretching (50% strain). The resistance remains virtually unchanged during 200 days in everyday environments. Furthermore, the excellent conformability and breathability of the flexible transparent electrode attached to the human skin demonstrates its potential application as an e-skin sensor. Our findings reliably urge a simple approach to underscore better outcomes with effective patterns by self-assembly of AgNW for highly conformal wearable electronics.

Ultrathin alternating multilayered silver nanowire-coated electrospinning films for excellent electromagnetic interference shielding and robust mechanical properties

Developing an ultra-thin flexible polymer film with simultaneously excellent electromagnetic interference (EMI) shielding performance and satisfactory mechanical property is still urgently demanded but challenging for integrated and miniaturized electronics. Herein, alternating multilayered silver nanowire-coating polyvinyl alcohol/ferroferric oxide@silver nanowires (PVA/Fe3O4@AgNW) composite films were successfully fabricated through spraying AgNWs on electrospinning PVA/Fe3O4 films, followed by hot pressing the alternately stacked monolayer PVA/Fe3O4 and PVA/Fe3O4@AgNW films in total of 6 layers. Stemming from superior conductive AgNW networks, alternating multilayered PVA/10-Fe3O4@10-AgNW composite film exhibits the prominent electrical conductivity of 1.5 × 105 S/m. Noteworthily, 6-layered PVA/10-Fe3O4@10-AgNW composite film with a thickness of 30 μm displays excellent EMI shielding effectiveness (SE) of 80.8 dB, on account of the unique alternating multilayered architectures and synergistic effect of conductive AgNWs and magnetic Fe3O4. Furthermore, 6-layered PVA/10-Fe3O4@10-AgNW film possesses satisfactory tensile strength (16.7 MPa) as well as superb flexibility (The fracture strain is 200.6 %). This effort sheds a new avenue for ultrathin flexible electrospinning films with both high EMI SE and remarkable flexibility, which has potential application in intelligent, wearable, and portable electronics.

Contact resistance effects on current path and thermal characteristics of Ag-nanowire network

In this study, we measured the temperature distribution of Joule-heated Ag-NW network using thermoreflectance imaging (TRI). Numerical computation was conducted for the electric current flow and heat transfer of the Ag-NW network. The contact electric resistance was obtained by solving the optimization problem to minimize the difference between the temperature distributions of the measurement and computation. The results showed that the contact electric resistance varies over the Ag-NW network at certain magnitude. This variation significantly affected the temperature distribution by defining the current path and producing a non-uniform current distribution.

High-performance composite transparent electrode composed of ultra-long silver nanowires and antimony-doped tin oxide nanoparticles

Composite transparent conductive electrodes (TCEs) consisting of silver nanowires (AgNWs) and conductive metal oxides are very promising for flexible optoelectronic devices due to their smooth surface morphology and high chemical stability. However, it is still challenging to ensure high optoelectronic performance and long-term stability in practical applications. Here, we solved these problems by coating antimony-doped tin oxide (ATO) nanoparticles dispersion on ultra-long AgNWs network using waterborne polyurethane (WPU) binder. Ultra-long nanowires occupy less wire-wire junctions and space than short nanowires, thus increasing the optoelectronic performance and flexibility of the composite TCE. WPU improves the adhesion and stability of ATO nanoparticles to the substrate and AgNWs network. The fabricated composite TCE showed a low sheet resistance of 11.9 Ω sq−1, good optical transmittance of 83% at 550 nm and a figure of merit (FOM) of 162 compared to PET/ITO electrode. It also showed excellent mechanical flexibility, adhesion to the substrate and solvent stability. Furthermore, the long-term conductivity was maintained under ambient conditions for 60 days.

Analysis of the characteristics of silver nanowires (AgNW) random network for transparent heater applications

Transparent heaters (THs) find widespread application in various indoor and outdoor settings, such as LCD panels and motorcycle helmet visors. Among the materials used for efficient TH performance, the AgNW network stands out due to its high conductivity, substantial transmittance, and minimal solution requirement. Extensive research has been directed towards enhancing AgNW characteristics, focusing on smaller diameters and longer wires. In TH applications, the primary considerations include a rapid response and elevated temperature. Consequently, this research delves into investigating the impact of parameters like diameter, length, and density on random AgNW networks under varying applied voltages. The finite element method is employed for analyzing temperature changes in response to voltage application, particularly in scenarios involving small-scale setups with high-density and high-percolation AgNW networks. The results reveal a significant increase in the thermal transition rate, ranging from 28% to 36%, with varying densities in the random network. Within the same density, the AgNW network with larger diameters and lengths demonstrates the highest temperatures, aligning with previous calculations. Furthermore, a trade-off exists between optical properties in smaller diameters and electrical properties in larger diameters within a relatively narrow temperature range.

Uniform and welded networks of silver nanowires surface-embedded on cellulose yarns with PEDOT:PSS passivation for sustainable E-textiles

Electronic textiles are critical for wearable electronics and real-time health care monitoring. The use of cellulose fibers with conductive components to construct optimized materials for enhanced performance remains an ongoing mission. We report the use of continuous dip-coating of hydrogel fibers to fabricate conductive cellulose yarns (CCYs). Uniform, interwelded and compact silver nanowire (AgNW) networks are embedded on the surfaces of the cellulose yarns, after which a PEDOT:PSS passivation layer is applied to ensure the reliability and practicality of the CCYs. This unique AgNW network provids high electrical conductivity of the CCYs, high strain sensitivities and good Joule heating. Wearable fabric devices embroidered with CCYs exhibit superior performance in strain sensing and electrothermal insulation. This CCY realizes the organic combination of manufacturing, practicability and functionality in sustainable E-textiles. The CCY has the potential to enable scalable manufacturing of low-cost wearable sensors integrated into everyday clothes.

Multilayer ordered silver nanowire network films by self‐driven climbing for large‐area flexible optoelectronic devices

AbstractSilver nanowire (AgNW) networks hold great promises as next‐generation flexible transparent electrodes (FTEs) for high‐performance flexible optoelectronic devices. However, achieving large‐area flexible AgNW network electrodes with low sheet resistance, high optical transmittance, and a smooth surface remains a grand challenge. Here, we report a straightforward and cost‐effective roll‐to‐roll method that includes interface assembly/wetting‐induced climbing transfer, nanowelding, and washing processess to fabricate flexible ordered layered AgNW electrodes with high network uniformity. By manipulating the stacking number of the interfacially assembled AgNW monolayer, we can precisely tailor and balance the transparency and the conductivity of the electrodes, achieving an exceptional Figure of Merit (FoM) value of 862. Moreover, the ordered layered structure enhances surface smoothness, compared with randomly arranged structures. To highlight the potential of these ordered layered AgNW network electrodes in flexible optoelectronic devices, we successfully employ them as highly sensitive strain sensors, large‐area flexible touch screens, and flexible smart windows. Overall, this work represents a substantial advance toward high‐performance FTEs over large areas, opening up exciting opportunities for the development of advanced optoelectronic devices.image

Multilayered silver nanowires and graphene fluoride-based aramid nanofibers for excellent thermoconductive electromagnetic interference shielding materials with low-reflection

Multilayered films composed of alternating layers of graphene fluoride (GF) and silver nanowires (AgNWs) in an aramid nanofiber (ANF) matrix were fabricated. The films were prepared by sequential vacuum filtration of GF@ANF and AgNWs@ANF suspensions to obtain multilayered composite architectures. The multilayered GF@ANF/AgNWs@ANF films exhibited exceptional mechanical flexibility and strength, with tensile strength up to 130 MPa and 5000 bending cycles with negligible performance deterioration. The films displayed remarkably high electromagnetic interference (EMI) shielding effectiveness up to 54 dB in X-band frequencies, attributed to the multiple internal reflections in the multilayered structure. EMI shielding was dominated by absorption rather than reflection, enabling attenuation of incident microwaves without secondary pollution. The multilayered films also exhibited ultrahigh in-plane thermal conductivity of up to 45 W/mK, owing to the thermally conductive GF and AgNWs networks. The EMI shielding effectiveness and thermal conductivity were retained after temperature and bending cycling. The composite films also demonstrated excellent flame retardancy. This study provides an effective route toward concurrent enhancement of multi-functional properties through architectural engineering at the nanoscale. The combination of robust EMI shielding, mechanical flexibility, thermal management, and fire safety highlights the potential of rationally designed multilayered composites for practical applications in 5 G wearable electronics devices, communications systems, and radar technologies.

Conductivity enhancement of Ag nanowire ink by decorating in situ formed Ag particles under low-temperature sintering

Silver nanowires (AgNWs) have attractive applications in the fabrication of flexible electronics because of their adequate electrical conductivity, mechanical properties, and oxidation resistance. However, the film produced by AgNW ink needs to be sintered at temperatures above 200 °C to obtain high electrical conductivity, which is incompatible with commonly used flexible substrates such as paper or polymer materials. In this study, the AgNW network was decorated by in situ reduced Ag particles (AgPs) to improve the structural integrity and conductivity of the film. After sintering at 80 °C, the pores and voids within the AgNW network were filled with Ag particles smaller than 200 nm, and the porosity of the film was markedly reduced. The lowest resistivity value was 3.9 × 10–5 Ω cm after sintering at 100 °C, only 10.8% and 8.5% of the resistivity values of the films produced from AgNW and ion inks, respectively. During sintering, Ag nucleated on the surface of AgNWs, and its growth and agglomeration resulted in interconnections between the AgNWs and Ag particles. Thereafter, the bridging and filling effect of the Ag particles facilitated the formation of a compact and firm network, improving the film conductivity. The line film printed from the composite ink with 10 layers exhibited a low resistivity of 7.3 × 10–7 Ω·m. Even after 5000 bending cycles, the resistivity of the line only increased by 4.47 × 10–6 Ω·cm from the initial value. The composite ink reported in this study is a promising candidate for the low-cost printing of ultralow-power-consumption wearable electronic devices.

Self-Assembled Monolayer and Nanoparticles Coenhanced Fragmented Silver Nanowire Network Memristor.

Silver nanowire (AgNW) networks with self-assembled structures and synaptic connectivity have been recently reported for constructing neuromorphic memristors. However, resistive switching at the cross-point junctions of the network is unstable due to locally enhanced Joule heating and the Gibbs-Thomson effect, which poses an obstacle to the integration of threshold switching and memory function in the same AgNW memristor. Here, fragmented AgNW networks combined with Ag nanoparticles (AgNPs) and mercapto self-assembled monolayers (SAMs) are devised to construct memristors with stable threshold switching and memory behavior. In the above design, the planar gaps between NW segments are for resistive switching, the AgNPs act as metal islands in the gaps to reduce threshold voltage (Vth) and holding voltage (Vhold), and the SAMs suppress surface atom diffusion to avoid Oswald ripening of the AgNPs, which improves switching stability. The fragmented NW-NP/SAM memristors not only circumvent the side effects of conventional NW-stacked junctions to provide durable threshold switching at >Vth but also exhibit synaptic characteristics such as long-term potentiation at ultralow voltage (≪Vth). The combination of NW segments, nanoparticles, and SAMs blazes a new trail for integrating artificial neurons and synapses in AgNW network memristors.