Inkjet-printed Silver Nanoparticle Research Articles

Low-temperature characterization of inkjet printed silver nanoparticles on polyimide substrate for the temperature range of −5°C to −75°C

Drop-on-demand inkjet printing is an additive manufacturing method capable of fabricating electronic devices using custom geometries at a relatively low cost. Drop-on-demand using silver nanoparticles has been extensively studied to produce devices and sensors that operate at room conditions. This work investigates the survivability and performance of inkjet-fabricated silver traces tested in an electric circuit at a subzero temperature environment from −5℃ to −75℃. Results show that printed Ag nanoparticles exhibit a similar thermal resistance coefficient compared to literature values of bulk nanostructured Silver at subzero temperatures, rendering this additive manufacturing technology a strong candidate for creating microelectronic devices for low-temperature aerospace applications.

Systematic Investigation of Novel, Controlled Low-Temperature Sintering Processes for Inkjet Printed Silver Nanoparticle Ink.

Functional inks enable manufacturing of flexible electronic devices by means of printing technology. Silver nanoparticle (Ag NP) ink is widely used for printing conductive components. A sintering process is required to obtain sufficient conductivity. Thermal sintering is the most commonly used method, but the heat must be carefully applied to avoid damaging low-temperature substrates such as polymer films. In this work, two alternative sintering methods, damp heat sintering and water sintering are systematically investigated for inkjet-printed Ag tracks on polymer substrates. Both methods allow sintering polyvinyl pyrrolidone (PVP) capped Ag NPs at 85°C. In this way, the resistance is significantly reduced to only 1.7 times that of the samples on polyimide sintered in an oven at 250°C. The microstructure of sintered Ag NPs is analyzed. Taking the states of the capping layer under different conditions into account, the explanation of the sintering mechanism of Ag NPs at low temperatures is presented. Overall, both damp heat sintering and water sintering are viable options for achieving high conductivity of printed Ag tracks. They can broaden the range of substrates available for flexible electronic device fabrication while mitigating substrate damage risks. The choice between them depends on the specific application and the substrateused.

Effect of pulse overlapping on temperature field and physical characteristics in pulsed laser sintering of inkjet-printed silver nanoparticles

Pulsed laser sintering of metal nanoparticles (NPs) has been studied owing to its minimal impact on heat-sensitive zones. The characteristic effects of pulse overlapping during pulsed laser sintering of metal NPs on metal NP surface morphology and electrical properties have not been reported to date. We therefore investigated millisecond pulsed laser sintering of inkjet-printed silver (Ag) NP lines at 30, 50, 70, 80, and 90% pulse overlaps (POs). We then assessed the thermal, electrical, and surface-morphological characteristics for each PO case. The temperature history was investigated via numerical analysis using a designed algorithm for treating thermal conductivity. The 70% PO produced the lowest Ag NP line resistivity with the highest degree of consistency as a result of the uniform temperature distribution and relatively continuous surface morphology with minimal porosity. The results of this study can guide the understanding of the thermal response, electrical performance, and surface morphology of Ag NPs corresponding to pulse overlapping during a pulsed laser sintering operation.

Optical transparent metasurface for dual-band Wi-Fi shielding.

An optical transparent metasurface for dual-band Wi-Fi shielding is presented in this paper. The unit cell of the proposed metasurface is composed of a hexagonal ring and a three-petal oval flower which resonate at 2.4 and 5.5 GHz, respectively. The corresponding equivalent circuit is modelled to better understand the physical phenomena of electromagnetic shielding. Based on transmission line theory and curve fitting technique, a convenient and efficient method for extracting permittivity of substrate is presented. Simulation results show that the proposed metasurface is insensitive to the polarization of incoming wave under normal incidence and offers excellent angular stability. For verifying the design, two prototypes are fabricated using different manufacturing technologies, flexible printed circuit and ink-jet printing of silver nano-particles. The measured results are in good agreement with the simulated ones. The proposed metasurface has potential applications of electromagnetic wave suppression and information security in indoor environments.

Hybrid additive manufacture: Surface finishing methods for improving conductivity of inkjet printed tracks on non-planar substrates fabricated using fused deposition modeling

This study investigates the impact of the surface quality of 3D printed non-planar surfaces on the conductivity of an inkjet-printed silver nano-particle ink, in the context of fused deposition modeling; a type of additive manufacture (3D pritnting). It was observed that the as-printed surface finish resulted in continuity breaks together with reduced and overall poor batch consistency of conductivity (SDbatch = 16.51 mS/mm). Therefore, to pave the way for high density, consistent and repeatable electronic tracks, the surface finish of as-printed 3D printed parts must be improved. To mitigate this, several finishing methods were investigated, CNC machining, non-planar nozzle ironing and the technique of burnishing with a custom-made heated tool. Of all the investigated finishing techniques, burnishing was identified as the most effective solution that ensured a high and consistent conductivity across the surface for subsequently printed nanoparticle tracks (SDbatch = 2.88 mS/mm). The combination of non-planar burnishing and non-planar printed electronics is key to unlocking the possibility of completely embedded 3D electronics and sensors in 3D printed objects and components.

Enhancing the electrical properties of inkjet-printed silver ink by electrolyte sintering, photonic sintering, and electroless plating

Conductive inkjet printing is an emerging rapid manufacturing technology in the field of smart clothing and wearable electronics. The current challenge in conductive inkjet printing includes upgrading of electrical performance of printed inks to the equivalent level to traditional conductors such as bulk silver and copper, especially for high-performance electronic applications such as flexible antennas and circuits. Post-treatments are commonly employed to enhance the electrical conduction of inkjet-printed tracks. This research discusses the effects of electrolyte sintering, photonic sintering and electroless copper plating on the DC electrical resistance and resistivity of inkjet-printed silver nanoparticles. From experimental results and measurements, it was found that all the post-treatment methods effectively improved the electrical properties of printed silver ink, but in different ways. The lowest resistance of 4.5 ? (in 0.1 mm ? 10 mm) and thickest (4.5 ?m) conductor were achieved by electroless copper plating, whereas the lowest resistivity (7.5?10-8 ??m) and thinnest (1.0 ?m) conductor were obtained by photonic sintering.

Inkjet printed silver nanoparticles on hydrophobic papers for efficient detection of thiram.

Silver nanoparticles coated paper (AgNPs-paper) substrates were prepared by inkjet printing Ag ink on four different wettability papers. Scanning electron microscope and contact angle analyzer were used to characterize their surface morphology and wettability. AgNPs-paper substrates were used to detect the surface-enhanced Raman scattering (SERS) spectra of thiram aqueous solution. Relationships between the surface wettability, surface morphology and SERS activities of the substrates were systematically studied. The silver nanoparticles deposited on the hydrophobic papers (photographic paper, graph paper, and weighing paper) were evenly and densely arranged. While in-homogeneous distribution was observed on the hydrophilic printing paper. It can be found that the AgNPs-photographic paper with the maximum contact angle exhibited the highest SERS enhancement. The detection limit for thiram adsorbed on the AgNPs-photographic paper was 10-10mol/L, which was lower than the others. Good linear responses (R2=0.9918, 0.9897) between the SERS intensities and logarithmic concentrations were obtained from 104 to 10-10mol/L. Moreover, the substrate had good uniformity and reproducibility with relative standard deviation values of 4.20% and 4.90% measured by eight points and ten substrates, respectively. The AgNPs-photographic paper exhibited high stability within eight months.

Evaluation of the Sheet Resistance of Inkjet-Printed Ag-Layers on Flexible, Uncoated Paper Substrates Using Van-der-Pauw's Method.

With the growing significance of printed sensors on the electronics market, new demands on quality and reproducibility have arisen. While most printing processes on standard substrates (e.g., Polyethylene terephthalate (PET)) are well-defined, the printing on substrates with rather porous, fibrous and rough surfaces (e.g., uncoated paper) contains new challenges. Especially in the case of inkjet-printing and other deposition techniques that require low-viscous nanoparticle inks the solvents and deposition materials might be absorbed, inhibiting the formation of homogeneous conductive layers. As part of this work, the sheet resistance of sintered inkjet-printed conductive silver (Ag-) nanoparticle cross structures on two different, commercially available, uncoated paper substrates using Van-der-Pauw’s method is evaluated. The results are compared to the conductivity of well-studied, white heat stabilised and treated PET foil. While the sheet resistance on PET substrate is highly reproducible and the variations are solely process-dependent, the sheet resistance on uncoated paper depends more on the substrate properties themselves. The results indicate that the achievable conductivity as well as the reproducibility decrease with increasing substrate porosity and fibrousness.

Multi-parameter paper sensor fabricated by inkjet-printed silver nanoparticle ink and PEDOT:PSS

This work presents the evaluation of a multiparametric sensing device on paper fabricated by inkjet printing, for applications such as smart packaging-labeling and disposable biosensors where biocompatibility and low cost are key factors. The device is able to measure simultaneously relative humidity, temperature and compressive and tensile bending. Commercial silver nanoparticle ink and PEDOT:PSS were printed onto inkjet photo glossy paper using a drop-on-demand inkjet printer forming an interdigitated electrode array and a meander shaped micro-ribbon. Humidity measurements revealed that sensor response, which is effectively expressed by the relationship between paper substrate resistance and relative humidity was similar for both materials utilized as electrodes. Temperature coefficients of resistance (TCR) were extracted for Ag-nanoparticle and PEDOT:PSS - based temperature sensors respectively in the range of 25–45 °C. The bending tests indicated that both materials exhibited similar trend in tensile bending, with resistance increasing in a linear manner up to a maximum tensile length of 900 μm. Ag-nanoparticle ink outperformed PEDOT:PSS ink in terms of repeatability, sensitivity and hysteresis. In compressive bending measurements Ag-nanoparticle and PEDOT:PSS gauge factors exhibited similar gauge factor of opposite sign.

Conductivity and Stretchability of Inkjet-Printed Silver Nanoparticle Patterns: Effect of the Number of Printed Layers

Conductivity and Stretchability of Inkjet-Printed Silver Nanoparticle Patterns: Effect of the Number of Printed Layers

Optimization of Geometry Parameters of Inkjet-Printed Silver Nanoparticle Traces on PDMS Substrates Using Response Surface Methodology.

Inkjet printing is an emerging technology with key advantages that make it suitable for the fabrication of stretchable circuits. Specifically, this process is cost-effective and less complex compared to conventional fabrication technologies. Inkjet printing has several process and geometry parameters that significantly affect the electromechanical properties of the printed circuits. This study aims to optimize the geometry parameters of inkjet-printed silver nanoparticle traces on plasma-treated polydimethylsiloxane (PDMS) substrates. The optimization process was conducted for two printed shapes, namely straight line and horseshoe patterns. The examined input factors for the straight line traces were: the number of inkjet-printed layers and line width. On the other hand, the number of cycles and amplitude were the examined input parameters for the horseshoe shape. First, the optimal number of layers and line width were found from the straight line analysis and subsequently were used in the optimization of the horseshoe pattern parameters. The optimization of the input parameters was carried out using the response surface methodology (RSM), where the objective of the optimization was to maximize the breakdown strain of the traces while maximizing the gauge factor and minimizing the ink cost. The results indicate that a 1.78 mm line width and one layer are the optimal geometry parameters for the straight line traces, while for the horseshoe pattern, the optimal parameters are one layer, a line width of 1.78 mm, amplitude of 4 mm and one cycle. The optimal straight line was designed to sustain up to 10% strain while the horseshoe pattern was designed to sustain up to 15% strain.

Inkjet printing and characterisation of a resistive temperature sensor on paper substrate

Resistive temperature sensors on two different commercially available uncoated paper substrates have been manufactured using inkjet printing of silver nanoparticles. Their dedication is to be integrated in lightweight materials made from natural fibre-reinforced biopolymers for condition monitoring during the manufacturing process and beyond. The printed sensors have nominal resistances of a few hundred Ohms and kOhms, depending on the roughness and porosity of the respective paper substrate. Compared to previous research in this field, the manufactured sensors were fully characterised and extensively tested as part of this work. Furthermore, the influence of the individual paper characteristics on the electrical properties was studied using white-light interferometry and SEM imaging. All sensors show a good linear temperature dependence, minimal hysteresis and low baseline drift in the temperature range of interest (20 °C–80 °C). In an extended temperature range (−25 °C to 150 °C) and exposed to humidity (0%rH–80%rH) the accuracy and overall quality of the sensors decrease expectedly, still the temperature sensing principle can be exploited depending on the individual application and precision requirements.

Reliability of inkjet printed silver nanoparticle interconnects on deformable substrates tested through an electromechanical in-situ technique

Abstract

Electrically-generated memristor based on inkjet printed silver nanoparticles.

A method to electrically induce memristor performance from inkjet-printed silver (Ag) nanoparticles is presented, which is effective on a specifically designed hourglass-shaped Ag metal device. Joule heating-induced oxidation in the bottleneck region, when applying a high current to the device, results in a metal-electrolyte-metal structure produced from just a single metal ink for the memristor operation. This electrically induced memristor shows a nonuniform dispersion of the Ag nanoparticles within the oxide electrolyte layer, depending on the bias polarity adopted during the initial metal rupture process. A versatile and useful range of controllable memristor behaviors, from volatile threshold switching to nonvolatile unipolar as well as bipolar resistive switching, are observed based on the reversible rejuvenation and rupture of the Ag nanofilaments according to the Ag cation migration within the oxide electrolyte. The interplay between the electric field induced redox reaction and thermal diffusion of the Ag nanoparticles constitutes the primary reason for the different switching behaviors, further supported by thermo-field simulation results. The bipolar switching memristor demonstrates reliable endurance even under harsh DC switching conditions with low power consumption compared with its unipolar switching operation. The observed range of controllable switching behavior can be exploited for future low power flexible memory, as a selector in crossbar memory architecture, synaptic learning, and others.

Selective laser sintering of inkjet-printed silver nanoparticle inks on paper substrates to achieve highly conductive patterns

Development of cost-effective and environmentally friendly manufacturing methods will enable important advances for the production of large-scale flexible electronics. Laser processing has shown to be a promising candidate that offers a fast and non-destructive way to produce highly conductive patterns on flexible substrates such as plastics. However, an emerging option with a lower environmental impact is instead the use of cellulose-based flexible substrates, such as paper. In this work we investigate the use of laser sintering of silver nanoparticle inks, which were inkjet-printed on three different types of paper. Patterns with a high conductivity could be manufactured where a special care was taken to prevent the substrates from damage by the intense laser light. We found that the best results was obtained for a photopaper, with a conductivity of 1.63 ∗ 107 S/m corresponding to nearly 26% of the bulk silver conductivity. In addition, we demonstrate laser sintering to fabricate a fully functional near field communication tag printed on a photopaper. Our results can have an important bearing for the development of cost-effective and environmentally friendly production methods for flexible electronics on a large scale.

Stretchable Electronics: EGaIn‐Assisted Room‐Temperature Sintering of Silver Nanoparticles for Stretchable, Inkjet‐Printed, Thin‐Film Electronics (Adv. Mater. 29/2018)

In article number 1801852, Mahmoud Tavakoli, Carmel Majidi, and co-workers introduce a materials architecture and method for rapid fabrication of electronic tattoos that are highly flexible and stretchable. The tattoos are produced rapidly by combining ink-jetprinted silver nanoparticles with gallium–indium liquid-metal alloy. These ultrathin electronics can be populated with microelectronic components and be mounted on the skin or hydrographically transferred to a wide variety of 3D surfaces.

Optimized inkjet-printed silver nanoparticle films: theoretical and experimental investigations.

We study the influence of inkjet printing scheme and sintering parameter on the electrical resistivity of multi-layer silver nanoparticle films. A central composite Design Of Experiments (DOE) is employed to maximize experimental efficiency and improve the statistical significance of parameter estimates. The resulting mathematical correlations allow to interpret the influence of the print and sintering parameters. Detailed inspection of the correlations reveals the existence of local extrema and indicates that a structured approach such as the DOE would be significantly more effective for fabricating films with a minimum of resistivity. Furthermore, we modify the well-known Fuchs–Sondheimer Mayadas–Shatzkes model to correlate the resistivity of a multi-layer nanoparticle film with the sintering temperature and time. The modified model uses literature data but one constant inferred from two experiments. After model adjustment, the resistivities of films fabricated with different parameters can be predicted with good accuracy. This validation tremendously increases applicability and relevance of the model.

Controlling the crack formation in inkjet-printed silver nanoparticle thin-films for high resolution patterning using intense pulsed light treatment

During the last years, intense pulsed light (IPL) processing has been employed and studied intensively for the drying and sintering of metal nanoparticle layers deposited by means of printing methods on flexible polymer substrates. IPL was found to be a very fast and substrate-gentle approach qualified for the field of flexible and large-area printed electronics, i.e. manufactured via roll-to-roll processing. In this contribution, IPL is used for the fine-patterning of printed silver nanoparticle layers. The patterning is obtained by induced and controlled crack formation in the thin silver layer due to the intense exposure of IPL. The crack formation is controlled by selection of the substrate material, the fine-tuning of the morphology of the silver layer and an application of a dielectric layer on top of the silver layer that acts as a stress concentrator. Careful optimization of the IPL parameters allowed to adjust the lateral width of the crack. This novel approach turned out to be a fast and reproducible high-resolution patterning process for multiple applications, e.g. to pattern the source-drain electrodes for all-inkjet-printed thin-film transistors.

Sintering strategies for inkjet printed metallic traces in 3D printed electronics

Emerging from 2D printed electronics, 3D printed electronics promise a break-through in additive manufacturing and prototyping of electronics. However, transferring the know-how from 2D flexible electronics to 3D parts with complex structures (e.g. internal vias and external interconnects) might not be a straightforward approach. As an example, the variation of light intensity with respect to the distance and angle of incidence casts doubt on the efficiency of the intense pulsed laser (IPL) as a robust sintering method for metallic traces in 3D printed bulk structures, whereas IPL is currently by far the most prevailing sintering technique for 2D printed flexible electronics. Sintering of metallic traces in 3D printed parts can be executed either as a sequential layer-by-layer printing and processing step (LP) or as a bulk post-processing step (BP). In the current study, a survey on the most common sintering strategies for inkjet printed silver nanoparticles was conducted, while the compatibility to 3D printed structures was brought into the focal point. To discover the capabilities and limitations of six sintering methods (i. e. IPL, ohmic curing, thermal heating, laser, atmospheric plasma and microwave sintering) for 3D printed electronics, a comparative study utilizing the same materials and diagnostic methods was pursued. The results revealed that for 3D functional parts, some of the sintering techniques can be considered as complementary methods for each other, whereas a few showed readily the potential to be adapted in 3D printed electronics production.

Homogeneous Surface Profiles of Inkjet-Printed Silver Nanoparticle Films by Regulating Their Drying Microenvironment

Obtaining homogeneous surface profiles of inkjet-printed silver nanoparticle films (SNFs) is severely hampered by the classical coffee-ring phenomenon. Traditional approaches to suppress the coffee-ring effect are achieved by improving the uniformity of liquid evaporation rate or introducing inward Marangoni force during ink drying. However, these existing methods involve extra chemicals, treatments, or equipment that will definitely increase the production cost or reduce conductivity. In this study, we demonstrate an inexpensive and efficient method to obtain uniform surface profiles of inkjet-printed SNFs by rationally regulating the drying microenvironment. To this end, a number of surface profiles of printed dots and lines, such as concave, convex, and flat, were first obtained via this method. The underlying principle of this method was then investigated by analytical calculations based on the simplified vapor diffusion model. Consequently, homogeneous surface profiles of inkjet-printed SNFs were ach...