Ag Patterns Research Articles

Fast In Situ Metal Deposition and Removal Under UV and Visible Light Using Polydopamine/TiO2 Composite Surface

AbstractMetal nanoparticles (MNPs) stand out owing to conspicuous catalytic activity, optical and electromagnetic properties, with applications ranging from photocatalysis to biosensor and photoelectric devices. Although photocatalysis with TiO2 has emerged as a promising technique for preparing MNPs, the low photocatalytic efficiency of TiO2 limits its practical utilization. Herein, a rapid photoreduction approach is presented to prepare MNPs under UV and visible light based on polydopamine (PDA)/TiO2 composite surface. It found that the PDA‐modified TiO2 substrate can greatly enhance the photocatalytic efficiency and stability of MNPs, leading to rapid and highly‐controllable preparation of MNPs. By this method, various Ag, Au, and Pd patterns with controllable metallization degree can be easily fabricated. In addition, the substrate can be effectively recycled through rapid photobleaching. This method will have a promising future in the preparation of MNPs for various applications.

A Comparative Study of Single and Dual Sintering Processes of Metal Nanoparticles for Flexible Electronics Application

The introduction of metallic nanoparticles (NPs) has revolutionized the fabrication of flexible electronic devices. Metallic NPs have numerous applications in the electronics industry due to their unique shape and size‐dependent properties compared to their bulk counterparts. However, the application of metallic NPs requires additional post‐processing procedures to remove stabilizing agents and additives, to achieve superior electrical conductivity. Herein, the sintering of printed metal NP patterns, including silver (Ag) and copper (Cu) NPs, fabricated on flexible polyimide substrates is explored using single and dual sintering methods. The single sintering methods involve exposing the printed metal NPs to either laser irradiation or thermal treatment. In the case of the dual sintering methods, one approach is to subject the printed metal patterns to thermal treatment followed by laser irradiation, while the other approach involves exposing the printed metal patterns to laser irradiation followed by thermal treatment. Moreover, this study identifies and compares the effects of these various sintering methods on the physical, electrical, chemical, and mechanical properties of the Ag and Cu NP patterns. Finally, the study suggests that dual sintering methods are more effective in improving the electrical conductivity and mechanical properties of the NP patterns under optimized sintering conditions.

Simple Isopropanol-Assisted Direct Soft Imprint Lithography for Residue-Free Microstructure Patterning.

A direct soft imprint lithography was proposed to realize the direct fabrication of residue-free, well-shaped functional patterns through a single step. This imprint method requires only a simply prepared isopropanol-treated polydimethylsiloxane (PDMS) stamp without any additional resists. Residue-free Ag patterns were successfully fabricated on different substrates by directly imprinting the Ag ink with the isopropanol-treated PDMS stamp. Furthermore, the coffee-ring effect of the imprinting Ag patterns can be eliminated by optimizing the imprinting time, isopropanol-treating time, and imprinting temperatures. Studies show that the residual Ag ink in the contact region can be absorbed by the isopropanol-treated PDMS stamp due to the "like dissolves like" principle. Finally, this method was employed to fabricate the Ag electrodes for the thin-film transistors, attaining a mobility of ∼8 cm2 V-1 s-1, which is comparable to those with vacuum-processed electrodes. This process provides a simple, low-cost, residue-free, coffee-ring-free, and fast patterning method in the field of microelectronics.

Ultralight Ag-grid current collector enabled by screen printing Ag ink on Cu foil as efficient deposition-inducing layer for dendrite-free lithium metal batteries

An ultralight deposition-inducing layer consisting of a grid-like Ag pattern on Cu foil was designed and fabricated by using a scalable screen-printing technique to guide a uniform lithium-plating behavior.

Reactive Aerosol Jet Printing of 2D and 3D Ag Patterns

Printed electronics is a rapidly growing field that involves the use of printing technologies to create electronic devices such as sensors, displays, and solar cells 1. Unlike traditional electronics, which rely on rigid and bulky components, printed electronics can be obtained on flexible and lightweight substrates such as plastic and paper, allowing the development of novel applications such as wearable electronics, smart packaging, and medical sensors. Printing technologies uniquely feature miniaturization and patterning capability at low-cost and high-throughput production. Among them, screen-printing, inkjet printing (IJP) and aerosol jet printing (AJP) are the most employed to fabricate conductive metallic patterns of Ag, Au, Cu and other metal nanoparticles (NPs). These printing techniques typically requires concentrated ink of metal NPs. However, specially in the case of IJP and AJP the synthesis of very small NPs (d < 100 nm) as well as proper ink formulation and long-time stability are major limitations to printing conductive metallic patterns 2.In this work, we propose an innovative method to produce 2D and 3D patterns and structures of Ag NPs by reactive Aerosol Jet Printing (r-AJP) on different substrates, using a custom-built aerosol jet printer. Ag NPs were in-situ reduced coupling two aerosol streams carrying the Ag precursor and a reducing agent, respectively. The process is fast, scalable and cheap. The electrical properties, in terms of both linear and areal electrical conductivity, of the r-AJP silver structures metallization patterns were investigated. Furthermore, the effect of both process parameters and precursor solution physical properties on printed Ag structure and morphology was assessed by x-ray diffraction (XRD) and scanning electron microscopy (SEM) in order to define the optimized condition for high definition 2d and 3D patterns by r-AJP. Bibliography P. Martins et al., Advanced Functional Materials, 33, 2213744 (2023).Y. Sui and C. A. Zorman, J. Electrochem. Soc., 167, 037571 (2020).

Pressureless sinter-joining of micron-Ag flake pastes at 160 °C enabled by solvent and interface engineering

Pressureless sinter-joining of cost-effective micron-Ag flake pastes at temperatures below 200 °C poses significant challenges due to their poor surface activity and low tapped density. Herein, we propose a novel solvent and interface engineering approach to enhance the contact among adjacent micron-Ag flakes and between the flakes and substrates. The solvent-enhanced sintering process is proposed, and its effect on the resistivity and shear strength of sintered Ag patterns and joints is studied in detail. Results show that the solvents with high wetting abilities on the Ag flakes and substrates are instrumental in achieving low resistivity and high shear strength in the sintered Ag patterns and joints. In particular, when the solvents possess high surface tension, they generate strong capillary adhesion among Ag flakes and substrates. This reduces the gap between Ag flakes and substrates, thereby promoting bonding among the Ag flakes by minimizing the distance of atom diffusion. Finally, mixed solvents of 50 % α-Terpineol and 50 % dipropyleneglycol methyl ether acetate show a synergistic effect due to the balance between wettability and surface tension, which enables the sintered joints to achieve an exceptional shear strength of 27 MPa even at an ultralow temperature of 160 °C. This achievement represents the state-of-the-art pressureless sinter-joining of Ag pastes and holds promising potential for practical use in power electronic packaging applications.

Fabrication and Electrochemical Testing of Silver Pattern Cathodes for Proton Conducting It-SOFC

Dense silver (Ag) cathodes with different triple phase boundary (TPB; the interface of gas, electrolyte and electrode) length (LTPB) and electrode area (AELT) were fabricated by photolithography and E-beam evaporation over different proton-conducting electrolytes such as BaZr0.4Ce0.4Y0.1Yb0.1O3– δ (BZCYYb4411). A bi-layer lift-off resist method appears more versatile than single layer for successful pattern cathode fabrication. The electrochemical behaviors of Ag pattern cathodes over the BZCYYb4411 electrolyte were tested with counter electrode such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ and correlated against geometric features such as LTPB and AELT to understand the oxygen reduction kinetics and mechanism for proton conducting solid oxide fuel cells. Figure 1

Evaluation of IL-17F A7488G polymorphism in Helicobacter pylori-infected patients: a case-control study.

A total of 86 adults (in two H. pylori-positive and H. pylori-negative groups) were included in the study. To identify the infection, rapid urease test and polymerase chain reaction (PCR) were performed. The cagA gene was also evaluated as a bacterial virulence factor. PCR-restriction fragment length polymorphism was used to investigate the IL-17F A7488G polymorphism in gastric biopsies using the NlaIII enzyme. 96.5% of patients in both groups did not show any mutation and had AA genotype, and only three patients infected with cagA-carrying H. pylori strains had polymorphism in the IL-17F A7488G gene, which included AG (one case) and GG (two cases) patterns. No significant relationship was found between these polymorphisms in the two groups of H. pylori-positive and H. pylori-negative patients, while, interestingly, a significant difference was observed between the polymorphisms and the presence of the cagA gene. This report is one of the first to demonstrate the association of IL-17F A7488G polymorphism with H. pylori infection and the presence of the cagA gene. Although no significant association between IL-17F polymorphism and H. pylori infection was found in the population of this study, the patients with mutated genotypes were positive for the cagA gene, which was statistically significant. Therefore, the possibility of the role of pathogenic strains in causing mutations in cytokine genes is more conceivable.

Electrohydrodynamic Printing of Ultrafine and Highly Conductive Ag Electrodes for Various Flexible Electronics

AbstractSilver nanoparticle (AgNP) based inks are widely used in printed electronics to form conductive patterns. However, high resolution and high electrical conductivity are still hard to achieve at the same time for the patterning of AgNP‐based electrodes. Herein, Ag patterns with a high resolution of sub‐10 µm and a high conductivity are realized by the electrohydrodynamic (EHD) printing. The parameters including the composition of Ag ink, printing speed, voltage, and working height are carefully controlled to increase the resolution, and the process window of the cone jet mode is established. With the help of the finite element simulation, the generation mechanism of the Taylor cone is clarified. Ag electrodes with various patterns and shapes are easily produced, which exhibited excellent patterning qualities, such as superior uniformity and flatness, narrow spacing, and clear edge definition. Finally, flexible light‐emitting diode (LED) circuits, transparent heaters, and supercapacitors are fabricated by EHD printed Ag grid electrodes. These results indicate that this work provides a simple and scalable strategy for fabricating ordered metal conductive patterns in the emerging printed electronics.

TOP ELECTRODE INVESTIGATION OF OPV MODULES BASED ON P3HT:PC[60]BM FABRICATED VIA ROLL-TO-ROLL PROCESS

Solar photovoltaic (PV) cells allow the direct conversion of sunlight into electricity without CO2 emission. Finding a way to cheaply utilize the vast amount of solar energy is one of the biggest challenges for this technology. The organic photovoltaic cells (OPV) are based on solution-processed photoactive polymers and can be fabricated via roll-to-roll (R2R) processes, which allow high production throughput with low costs. CSEM Brasil is building the foundations of future high-tech industries in Brazil and one of our key technology development areas is OPV modules production using R2R coating. In this work, polymer solar cells based on P3HT: PC[60]BM were prepared by R2R coating (electron transport, active and hole transport layers – ETL, AL and HTL) and by screen printing (top silver electrode). In order to save material and give more transparency of the OPV module were compared and evaluated the performance of two different suppliers of Ag paste (A and B) in three different top contact configurations, solid, grid and honeycomb. Additionally, were compared two different screen suppliers (I and II) for screen printing process and the Ag paste drying time studied. The comparisons were made with modules with an active area of 21.6 cm2 (6 stripes serially connected). Photovoltaic performance was evaluated in terms of Ag paste and screens suppliers, Ag pattern and drying time. Finally, modules were encapsulated in a R2R laminator using a flexible barrier film and evaluated in terms of lifetime.

Molecular Dynamics Investigation of Hetero Coalescence between Two Ih Ag55 and Cu55 Clusters at Atomic Scale

AbstractMolecular dynamics simulations are performed to explore the coalescence of the two hetero magic Ag55 and Cu55 clusters having icosahedral packing at room temperature, and the structural changes of the alloying Ag–Cu clusters at elevated temperatures. The simulation results reveal the influence of the contacting distances and relative orientations between the two clusters on the coalescing processes as well as the packing patterns of the coalesced binary clusters on heating. The activation energy is used to describe the energy required to initiate the coalescence. The Lode–Nadai parameter's distributions of the coalesced clusters provide more insight into the loading states on the atoms during different stages. The results show that the two clusters appear to form the neck involving twist and “slip” in the initial stage of the coalescence, and the Ag atoms present significant diffusion along the facets of the Cu cluster. As the temperature increases, different packing structures including Icosahedron, core/shell metastable, core@partial‐shell, and half Cu‐half Ag patterns occur.

Ultrashort laser sintering of printed silver nanoparticles on thin, flexible, and porous substrates

The fabrication of low-cost and mechanically robust flexible electronic patterns has increasingly gained attention due to their growing applications in flexible displays, touch screen panels, medical devices, and solar cells. Such applications require cost-effective deposition of metals in a well-controlled manner potentially using nanoparticles (NPs). The presence of solvent and precursors in NP based inks impacts the electrical conductivity of the printed pattern and a post-processing heating step is typically performed to restore the electrical properties and structure of the material. We report printing with picolitre droplet volumes of silver (Ag) NPs on flexible substrates using an acoustic microdroplet dispenser. The low-cost, controlled deposition of Ag ink is performed at room temperature on photopaper, polyimide and clear polyimide substrates. A localized, ultrashort pulsed laser with minimal heat affected zone is employed to sinter printed Ag patterns. For comparison, oven sintering is performed, and the results are analysed with scanning electron microscopy, four-point probe and Hall measurements. The femtosecond laser sintering revealed highly organized, connected nanostructure that is not achievable with oven heating. A significant decrease in sheet resistance, up to 93% in Ag NPs on clear polyimide confirms the laser sintering improves the connectivity of the printed film and as a result, the electrical properties are enhanced. The surface morphology attained by the laser sintering process is interpreted to be due to a joining of NPs as a result of a solid-state diffusion process in the near surface region of NPs.

The effect of PVAc in silver ink for adhesion and conductivity of conductive pattern

The adhesion with substrate and conductivity of silver (Ag) conductive pattern are critical for practical applications of flexible electronic devices. Polymer vinyl acetate (PVAc) as an important solvent in Ag ink might largely improve the conductive pattern's adhesion property. However, the addition of PVAc in Ag ink also result in decreasing the patterns conductivity to about 210 ± 2 μΩ cm after infrared sintering at air atmosphere. Here, we found a facial method to eliminate the effect of the addition of PVAc for Ag conductive pattern. In this method, the thickness of PVAc layer coated on Ag particles surface was decreased via a washing treatment by ethanol mixed with acetone. After post-sintering treatment of ethanol brushing, a stable and conductive pattern was achieved. Owing to these treatments, compared with the blank sample, the adhesion of patterns was improved by the scratch test with higher damage force from 1 to 3.8 N. Meanwhile, the resistivity of the formed Ag pattern gradually decreased to 22 ± 0.5 μΩ cm after post-sintering treatment for 50 times, and this value did not change after bending 6000 times. The mechanism was given and confirmed by energy dispersive spectroscopy (EDS) analysis, indicating that the residual organic coatings on patterns had been taken away by the evaporation of alcohol molecular. LEDs pasted in the electronic circuit of our university badge were illuminated, indicating their wide application in the field of flexible electronic devices.

Optical Printing of Conductive Silver on Ultrasmooth Nanocellulose Paper for Flexible Electronics

The nanofibrillated cellulose paper (nanocellulose paper or nanopaper), which is flexible, transparent, ultrasmooth, and biodegradable, has emerged as a new substrate material for the next generation of paper‐based flexible electronics. Herein a visible light‐induced printing technique for depositing highly conductive silver (Ag) patterns on nanopaper is reported. The optical Ag printing process is simple to implement at room temperature and only requires nontoxic, low‐cost aqueous chemical solutions and an inexpensive light projection setup. The abundant carboxyl groups on the nanopaper enable efficient absorption of Ag+ions on the nanopaper surface for light‐induced reduction of Ag+into a thin film of densely packed silver nanoparticles (AgNPs). Chemical annealing of the deposited AgNPs further enhances the conductivity of the printed Ag patterns. The mechanical and electrical properties of the printed Ag patterns on nanopaper are characterized, and the application of the optical Ag printing technique fabricating the nanopaper‐based flexible circuits and electrochemical biosensors is also demonstrated. The optical printing technique will enable new designs and applications of nanopaper‐based flexible electronics.

Selective noble-metal deposition modulation on photocurable polydimethylsiloxane films for electronics device applications

Selective metal-vapor deposition on organic surfaces is an interesting phenomenon and is applicable to prepare fine metal patterns for various electronic and photonic devices based on vacuum evaporation without a shadow mask. However, selective metal-vapor deposition with photochromic diarylethenes has not been successful for noble metals such as Au, Ag and Cu, which are generally used in the electronics field. In this paper, we report deposition modulation of noble-metal vapor on a photocurable polydimethylsiloxane (PDMS) film. When Au, Ag or Cu was vacuum-deposited on the UV-curable PDMS, Au and Cu formed a film on the surface even on the uncured film. Ag, however, was desorbed from the uncured film, and a small amount of evaporated Ag atoms was absorbed into the film. This metal species dependence on metal-deposition/desorption tendency was correlated with the intrinsic vapor pressure of metal species; metals with a high vapor pressure tend to desorb. The uncured film with a small amount of Ag deposition was easily removed with a hexane rinse, leaving only Ag on the cured film. Using this principle, various Ag-film patterns were prepared by irradiating upon UV light with a photomask to form a cured pattern and using maskless Ag deposition. Furthermore, we succeeded in fabrication of fine Ag patterns with a width of several micron by UV-laser scanning and maskless Ag-vapor deposition. This method would be applied to the electrode/wiring for various electronic devices.

Synergistic and Diminutive Effects between Regium and Aerogen Bonds.

The aerogen bond is formed in complexes of HCN-XeF2 O and C2 H4 -XeF2 O. The lone pair on the N atom of HCN is a better electron donor in the aerogen bond than the π electron on the C=C bond of C2 H4 . The coinage substitution strengthens the aerogen bond in MCN-XeF2 O (M=Cu, Ag, and Au) and its enhancing effect becomes larger in the Au<Cu<Ag pattern. The aerogen bond is further enhanced by the regium bond in C2 H2 -MCN-XeF2 O and C2 H4 -MCN-XeF2 O, but is weakened by the regium bond in MCN-C2 H4 -XeF2 O and C2 (CN)4 -MCN-XeF2 O. Simultaneously, the regium bond is also strengthened or weakened in these triads. The synergistic and diminutive effects between regium and aerogen bonds have been explained by means of charge transfer and electrostatic potentials.

Chemical Patterning of Graphene via Metal-Assisted Highly Energetic Electron Irradiation for Graphene Homojunction-Based Gas Sensors.

To gain the target functionality of graphene for gas detection, nonfocused and large-scale compatible MeV electron beam irradiation on graphene with Ag patterns is innovatively adopted in air for chemical patterning of graphene. This strategy allows the metal-assisted site-specific oxidation of graphene to realize monolithically integrated graphene-chemically patterned graphene (CPG)-graphene homojunction-based gas sensors. The size-tunable CPG patterns can be mediated by regulating the size of Ag prepatterns. The impacts of highly energetic electron irradiation (HEEI) on graphene are summarized as follows: (i) the selective p-type doping and the defect generation of graphene by the HEEI-induced oxidation, (ii) the resistance of the homojunction devices manipulated by the HEEI dose, (iii) the band gap opening of graphene as well as the lowering of the Fermi level, (iv) the work function values for pristine graphene and CPG corresponding to 4.14 and 4.88 eV, respectively, and (v) graphene-CPG-graphene homojunction for NO2 gas, revealing an 839% enhanced gas response compared with that of the pristine graphene-based gas sensor.

Low-temperature large-area fabrication of ZnO nanowires on flexible plastic substrates by solution-processible metal-seeded hydrothermal growth

We have developed the low-temperature conformal ZnO nanowire fabrication on flexible plastic substrates by utilizing the solution-processible metal seed-assisted hydrothermal ZnO crystallization. Structural evolution of ZnO nanowires controlled by major parameters involving growth temperature, growth time, and seed coating condition, has been systematically investigated towards uniform and large-area growth of conformal ZnO nanowires. Direct ZnO nanowire growth on flexible plastics without undergoing the high-temperature seed sintering has been realized by developing the low-temperature Ag-seeded hydrothermal ZnO nanowire growth. The nanoporous Ag layer favorable for ZnO crystal nucleation and continued nanowire growth can be reduced from the Ag ion solution coating at the temperature as low as 130 °C. This tactfully enables the selective hydrothermal growth of ZnO nanowires on the Ag patterns on flexible plastics. Such an all-solution-processible low-temperature fabrication protocol may provide an essential and practical solution to develop many diverse applications including wearable and transparent electronics, sensors, and photocatalytic devices. As one example, we demonstrate that a transparent UV sensor can be devised based on the ZNW growth on the Ag micromesh electrode.

Thermal and Thermomechanical Behaviors of the Fan-Out Package With Embedded Ag Patterns

Fan-out wafer/panel level package (PLP) is an advanced package. Compared to the conventional package, its thickness is reduced, and electrical and thermal characteristics are improved, through the substitution of a substrate/interposer with a redistribution layer (RDL). However, its thermal and thermomechanical characteristics need to be improved and controlled more elaborately. In this article, six types of Ag patterns were embedded in the upper side of the fan-out package. Thermal emission was improved by building an efficient thermal conductive path, while warpage was improved by vertical symmetry and strain distribution. Overall, the large pattern in both fan-out and fan-in zones reduced the warpage and the pattern embedded in the fan-in zone efficiently improved the thermal emission. However, the pattern area should be designed by considering the overlapped areas with the through via interconnection or the embedded component in the fan-out zone. Because the embedded pattern with a large area is not necessarily a proper approach, an optimum pattern was studied with the simulation and measurement of the thermogram and warpage. The approach of the embedding pattern in the fan-out package is expected to improve its thermal and thermomechanical behaviors.

Selective laser ablation and patterning on Ag thin films with width and depth control

Silver (Ag) films were deposited on glass substrates by radio frequency (RF) magnetron sputtering and then ablated by a 532 nm nanosecond pulsed laser. The effects of laser fluence and defocusing amount on the width and depth of laser-ablated grooves on 100- and 600-nm-thick Ag films were systematically investigated under single- and multi-scan ablation. The results suggested that the Ag films could be successfully removed from the substrate owing to laser-induced thermoelastic force or vaporization. It was confirmed that laser fluence and defocusing amount played very important roles in controlling the width and depth of the laser-ablated grooves. In the present work, grooves with widths ranging from 53 to 196 μm and depths ranging from 56 to 196 nm were obtained on 100-nm-thick Ag films by single-scan laser ablation, and laser ablation or removal with controllable depths was realized on 600-nm-thick Ag films by adopting single- or multi-scan (i.e., scanning numbers of 1–6). Furthermore, square spiral Ag patterns were successfully obtained by single- and multi-scan laser ablation and showed good electrical conductivity in a simple circuit. This work may have great potential applications in various fields that demand width and depth control of laser ablation/removal.