Printed Silver Electrodes Research Articles

Direct inkjet printing of micro-scale silver electrodes on polydimethylsiloxane (PDMS) microchip

Recently, direct inkjet printing of conductive solutions has received much attention in the microfluidics and lab-on-a-chip community because of its low-cost and mask-free deposition of electrodes on various substrates. However, the investigation of micro-scale direct inkjet printing on the polydimethylsiloxane (PDMS) substrate has not been completed. Here we present a direct inkjet printing technique to produce narrow (40–90 µm) silver microelectrodes on PDMS. Extensive experimental characterization studies on the pattern uniformity and electrical properties of the printed silver lines are presented. The effect of major printing parameters such as drop spacing, sintering temperature and duration, platen temperature, and nozzle temperature have been thoroughly investigated. We also investigated multiple layer printing as well as the effects of thermal expansion and mechanical bending. In order to demonstrate the utility of the inkjet-printed silver microelectrode, we fabricated both quadruple and castellated electrodes, and conducted dielectrophoretic manipulation of microbeads. The results clearly show that the printed silver electrodes can be used for electrokinetic applications in PDMS microchip devices. We believe that the direct inkjet printing of silver ink on PDMS presented here can provide a very convenient way of creating microelectrodes on PDMS devices for a variety of applications in the MEMS, microfluidics, and lab-on-a-chip communities.

An investigation of contact resistance between carbon fiber/epoxy composite laminate and printed silver electrode for damage monitoring

An addressable conducting network (ACN) enables the structural condition to be monitored by the electrical resistance between electrodes on surface of CFRP (carbon fiber reinforced polymer) structure. To improve the reliability of ACN for damage detection, the contact resistance between the electrodes and CFRP laminates needs to be minimized. In this paper, the silver nanoparticles electrodes were fabricated via printed electronics techniques on CFRP composite. The contact resistance between the silver electrodes and CFRP was measured with respect to various fabrication conditions such as the sintering temperature of silver nanoink and the surface roughness of CFRP laminates. The interfaces between silver electrode and carbon fibers were observed using scanning electron microscope (SEM). From the study, it was found that the lowest contact resistance of 0.3664Ω could be achieved when the sintering temperature of the silver nanoink and surface roughness were 120°C and 230nm, respectively.

Flexible Fibrous Piezoelectric Sensors on Printed Silver Electrodes

Here, we report a facile fabrication of flexible piezoelectric sensors based on highly aligned poly(vinylidene fluoride) (PVDF) nanofibers and printed silver electrodes without any additional poling processes. One-dimensional (1-D) piezoelectric PVDF nanofibers are directly produced onto stamped and sprayed interdigitated electrodes by electrospinning. We studied here the effect of contact area between nanofibers and electrodes by controlling the surface roughness of electrode. PVDF sensors show increased piezoelectric responses with larger actual contact area of the interdigitated electrodes. The measured output voltage under periodic bending stress is up to about 1 V. It is expected that this facile method to fabricate the PVDF sensors can be used to integrate the energy harvesters into flexible and stretchable functional electronic devices.

Analysis of printed silver electrode on amorphous indium gallium zinc oxide

Silver (Ag) electrodes printed on amorphous indium gallium zinc oxide (a-InGaZnO) were investigated to analyze their effect on thin-film transistor (TFT) characteristics. The TFT characteristics of samples annealed at 250 °C deteriorated seriously owing to an aggregation of Ag. In addition, the TFT characteristics deteriorated even for 200 °C annealing with oxygen and nitrogen atmospheres. From measurements of secondary ion mass spectrometry and Fourier transform infrared spectroscopy, we found that carbon and hydrogen contained in printed Ag electrodes seriously affect the TFT characteristics. The reduction and protection against these impurities in Ag ink is the key point in the application of printed Ag electrodes to a-InGaZnO TFTs.

A study of the effects of drying and sintering on the performance of organic photovoltaic devices

The effects of different processing methods on the performance of organic photovoltaics (OPVs) for the hole extraction layer and printed metal layers were studied. Four different methods (hot plate, air oven, vacuum oven and far-infrared oven) were utilized to dry hole extraction layers formed from aqueous nano-particle dispersions. The far-infrared oven showed the best drying characteristics and the sheet resistance was 69Ω/□ in 240s. To sinter a screen printed silver electrode, six different methods (hot plate, air oven, vacuum oven, far-infrared oven, UV lamp and microwave oven) were employed. The microwave oven yielded the most effective sheet resistance drop, as low as 0.06Ω/□ in 20s when the power of the microwave oven was 400W. Using the fast processing methods developed in this study, the processing time can be reduced by about 40% without a loss in the performance of prepared devices.

Chip-on-foil devices for DNA analysis based on inkjet-printed silver electrodes

For a rapid on-site diagnosis of pathogens, low-cost chip-based devices are of great interest. Here, we report the successful fabrication of inkjet printed silver electrodes on polymer foils as disposable chips for molecular DNA analytics. In order to manufacture these electrode structures, silver nanoparticle inks were inkjet printed onto planar polypropylene substrates. Due to the low thermal stability of the foils, substrate preserving sintering techniques, including low temperature thermal sintering and low pressure argon plasma sintering, were implemented. Thus, sufficient electrical conductance of the printed structures at processing temperatures ≤100 °C was achieved. To test the applicability of the manufactured chips, specific capture DNA was immobilized within the gaps of the conductive electrode paths and hybridized in the next step with biotin-labeled target DNA. Subsequently, an enzymatically generated silver nanoparticle deposition was induced that bridges the electrode gap. This enabled both conductance measurement and gray value analysis as a fast, simple and robust electrical and optical read-out system. The proof-of-principle experiments successfully demonstrated the applicability of these convenient chip-on-foil devices for nucleic acid based pathogen detection.

Screen Printed Potentiometric Chloride Sensors

Potentiometric chloride sensors were fabricated by electrochemically chloridizing the surface of screen printed silver electrodes using amperostatic coulometry or asymmetric square wave voltammetry. In the case of coulometric chloridization, the effect of different chloride ion sources was also investigated. The response to chloride ions by each type of sensor was determined by measuring their potentials with respect to a commercial Ag/AgCl reference electrode over the chloride concentration range 1.8 to 3,545mg/L (approximately 50μM to 100mM). Results reveal that irrespective of fabrication method, all sensors exhibit near Nernstian responses with no significant relationships between fabrication and response parameters.

Integrated circuits using fully solution-processed organic TFT devices with printed silver electrodes

We have demonstrated fully solution-processed inverter, NAND and NOR circuits using pseudo-CMOS logic and p-type organic TFT devices with printed electrodes that were fabricated using ink-jet printed silver nanoparticle inks at low temperatures. In order to optimize the gate electrode profiles, we thoroughly assessed the surface wettability of the silver nanoparticle inks. The pseudo-CMOS inverter circuit exhibited exceptional switching characteristics with a high signal gain of 34 at a supply voltage of 20V. The NAND and NOR circuits also exhibited excellent logic characteristics, whereby the switching voltage was approximately VDD/2 with a high noise margin and short delay time of 12.5ms.

Graphene-based Flexible Field Effect Transistor with Inkjet Printed Silver Electrodes

Graphene-based Flexible Field Effect Transistor with Inkjet Printed Silver Electrodes

Roll to Plate Printed Stretchable Silver Electrode Using Single Walled Carbon Nanotube on Elastomeric Substrate

Stretchable electronics may open new applications in display, sensors and actuators. To attain the stretchable electronics, the ink formulation should be compatible with elastomeric substrates. Here, we present the formulation of silver nanoparticles and single walled carbon nanotubes (SWNTs) for printing stretchable silver electrodes on the elastomeric substrates. Highly conductive stretchable electrodes can be printed directly on the poly(styrene-b-butadiene-b-styrene) (PSBS) substrates by roll to plate (R2P) gravure printer. During the stretching test, R2P printed silver based stretchable electrodes show the high conductivity of 1000 S cm(-1) at 0.27 wt% of SWNT loading. Furthermore, the resistance of the printed silver electrode was not changed up to 15% of tensile strain.

Strain sensitivity and durability in p-type and n-type organic thin-film transistors with printed silver electrodes

Mechanical flexibility and compatibility of printing processes are key advantage that organic electronic devices have over conventional inorganic devices. However, one of the major remaining issues for organic devices is insufficient mechanical durability of printed electrodes. Here we have investigated the mechanical durability of both p-type and n-type organic thin-film transistors (TFTs) with ink-jet printed silver electrodes from silver nanoparticle inks. The modified silver nanoparticle inks enabled the strong adhesion to the underlying polymer layer, and the fabricated organic TFTs exhibited excellent reproducibility in the bending cycle tests. The strong channel length dependence on the strain sensitivity was observed in both p-type and n-type organic TFTs. The organic TFTs with a short-channel exhibited higher sensitivity to the bending strain. These results suggest that the flexible organic TFTs with printed silver electrodes have excellent mechanical durability and are useful for bending and strain sensors.

Profile Control of Inkjet Printed Silver Electrodes and Their Application to Organic Transistors

We report on the cross-sectional profile control of printed electrodes fabricated from silver nanoparticle inks with water-based solvents by inkjet printing. Systematically varying the ambient conditions and time for the drying process corresponded to changes in electrode shape. In general, lower humidity levels resulted in concave electrode profiles due to the coffee-ring effect, while higher humidity levels resulted in convex profiles. Printed capacitors with trapezoidal-shaped lower electrodes showed much better electrical breakdown strength than those with concave-shaped lower electrodes. Solution-processed organic thin-film transistors with trapezoidal gate electrodes operated reproducibly and exhibited good electrical characteristics with very low gate-leakage currents. The methods can be utilized in the fabrication of printed electronic devices with stacked layers, such as thin-film capacitors and transistors.

Porous silicon micro- and nanoparticles for printed humidity sensors

In this work, the feasibility of porous silicon particles for producing printed humidity sensors is examined. A proof of concept is provided by producing fully functional humidity sensors on a glass substrate by drop casting a particle solution on top of inkjet printed silver electrodes. Sensor sensitivity towards changes in relative humidity is examined. The results show that the sensors provide good sensitivity and reproducible results throughout the entire relative humidity range. In addition, negligibly small hysteresis accompanied by relatively fast response and recovery times is also demonstrated.

Low-Cost Hydrogen Sulfide Gas Sensor on Paper Substrates: Fabrication and Demonstration

Drop-cast deprotonated emeraldine base (poly)aniline (PANI)-copper chloride films on paper substrates containing ink-jet printed silver electrodes have been prepared and are shown to be promising low-cost gas-sensors for H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S at room temperature. These films showed large changes in the conductivity (three to four orders of magnitude) upon exposure to low concentrations of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S (10 ppm) due to the formation of CuS and concurrent protonation of PANI. This large response of the sensor can be explained by the relatively large roughness and porosity of this paper substrate. Furthermore, the minimum resistances are low enough to allow light emitting diode lamps to be switched on using a low-voltage battery, thus serving as a proof-of-concept for mass-produced H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S-sensors for, for example, the food packaging industry.

Fabrication Research on the Double Cathode-Conducting-Layer for Diode Field Emission Display with CNT Emitters

With printed silver electrode and etched indium tin oxide (ITO) stripe, the double cathode-conducting-layer was developed on the cathode back plane. The lower ITO electrodes were composed of divided ITO film covered on the cathode back plane and the upper silver electrode was formed by the sintered silver slurry. And the cathode insulation layer was used to separate the lower ITO electrodes and the upper silver electrodes. Carbon nanotube used as field emitters, the fabrication research on the field emission display panel was performed. The main function for the double cathode-conducting-layer was to decrease the cathode voltage drop on the upper silver electrodes on the cathode back plane. The sealed small size field emission display panel possessed better image display performance.

Inkjet-printed stretchable silver electrode on wave structured elastomeric substrate

We report high performance and stable inkjet-printed stretchable silver electrodes on wave structured elastomeric substrates. Highly conductive silver electrodes were deposited directly on a ultraviolet ozone treated polydimethylsiloxane (PDMS) substrates having vertical wavy structures. Adhesion between printed silver lines and PDMS surface has been enhanced by intentionally roughened PDMS surface with wire-electro discharge machined aluminum mold. During slow (16.7 μm/s) stretching test, resistance of the printed silver electrode was increased only by three times at 30% tensile strain. Inkjet-printed silver electrodes also showed good mechanical stability during 1000-time fast (1 mm/s) cycling test with 10% tensile strain, showing maximum resistance change of less than three times.

Inkjet Printed Silver Electrodes for Organic Thin-Film Transistors

Inkjet printing high resolution electrodes is crucial for printing low-cost and high performance organic thin film transistors (OTFTs). This paper reviews our recent studies on inkjet printing high resolution silver electrodes (both narrow electrodes and small gaps between the electrodes as OTFT channel length) from either a silver complex composition or a silver nanoparticles ink for OTFTs. High performance devices with a narrow electrode (&lt; 50 um) and a small channel length (&#x223C; 10 um) were demonstrated. OTFTs with these printed silver electrodes exhibited high performance.

Measurement of Mechanical Strength of Printed Silver Electrode Using A Microfluidic Device

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Dielectric Properties of a Printed Sol-Gel Matrix Composite

Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol–gel derived network. The exemplary optimization of the properties by varying the sol–gel precursor illustrates the potential of sol–gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response.

Chemically modified ink-jet printed silver electrodes for organic field-effect transistors

Modification of ink-jet printed silver source and drain electrodes for organic field-effect transistors (FETs) with the electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) was investigated. Solution-based deposition of F4TCNQ onto ink-jet printed silver electrodes formed using either a nanoparticle-based or a metal organic decomposition ink, lead to a greater than tenfold improvement in FET mobility. Using these modified electrodes with the organic semiconductor 6,13-bis(triisopropylsilylethynyl) pentacene yields devices with a charge carrier mobility up to 0.9 cm2 V−1 s−1 and a current on/off ratio of 106.