Thick-film Printing Technique Research Articles

A microfabricated nickel–hydrogen battery using thick film printing techniques

Abstract To utilize the distinctive cycle life and safety characteristics of the nickel–hydrogen chemistry while eliminating the high pressure limitations of conventional nickel–hydrogen cells, a microfabricated nickel–hydrogen battery using a low-pressure metal hydride for hydrogen storage is being developed for powering micro-electromechanical systems (MEMS) devices and for biomedical applications where the battery would be implanted within the body. Thick film printing techniques which are simple and low cost were used to fabricate this battery. Inks were developed for each of the different battery components, including the electrodes, current collectors and separator. SEM images on these printed components showed the desired characteristics for each. Positive electrode cycling tests were performed on the printed positive electrodes while cyclic voltammetry was used to characterize the printed negative electrodes. Consistent charge and discharge performance was observed during positive electrode cycling. Full cells with printed positive and negative assemblies were assembled and tested.

The effect of annealing on the sensing properties of porous silicon gas sensor: Use of screen-printed contacts

A gas sensor utilizing a porous silicon layer and a thick film printing technique, instead of thin film deposition and photolithographic methods for fabricating such a device, is presented. The contact structure consists of a printed silver metal grid on the top of the porous silicon surface and an aluminium ohmic contact at the bottom, which were formed by a screen-printed metallization process. Freshly prepared porous silicon (PS) surfaces have been modified with organic molecules (CH x groups) in a thermal process in order to replace the hydrogen termination by monolayers attached to the surface through Si–C bonds. In this work, we report the experimental results of a porous silicon based sensor whose contacts were treated at different temperatures, ranging from 200 to 750 °C, and the effect of this thermal process on the reorganization of the PS bond configuration.

Development of a dimethyl ether (DME) sensor using platinum nanoparticles and thick-film printing

A portable and cost-effective technique to measure the dimethyl ether (DME) concentrations has been developed. It is based on an electrochemical principle measuring the oxidation current of DME at an applied potential of +0.2V versus a Ag/AgCl reference electrode. Thick-film printing technique is used for the fabrication of this DME sensor, and platinum nanoparticles in the crystallite size of 5.5 nm are used for the modification of the working electrode surface. This modification enhances the sensor performance significantly leading to a higher sensitivity of the sensor comparing to bare platinum electrode. Evaluation and characterization of this sensor are carried out over the DME concentration range of 0-7% (v/v), and a linear relationship between sensor outputs and the DME concentrations with an average R(2) of 0.996 exists. The reproducibility of the sensor is also very good. This electrochemically based DME sensor fabricated by thick-film screen printing technique and using the platinum nanoparticles to enhance its performance will be valuable and practical for the estimation of the airway mucosal blood flow.

A Microfabricated Nickel-Hydrogen Battery Using Thick Film Printing Techniques

To utilize the distinctive cycle life and safety characteristics of the nickel-hydrogen chemistry while eliminating conventional high pressure limitations, a microfabricated nickel-hydrogen battery using low-pressure metal hydride for hydrogen storage was proposed. Thick film printing techniques which are simple and low cost were used to fabricate this proposed battery. Inks were developed for the different battery components, including electrodes, current collectors and separator, and SEM images on these printed components showed the desired characteristics for each. Positive electrode cycling tests were performed on the printed positive electrodes while cyclic voltammetry was used to characterize the printed negative electrodes. Consistent charge and discharge performance was observed during positive electrode cycling. Full cells with printed positive and negative assemblies were assembled and tested for cycling.

Different thick-film methods in printing of one-electrode semiconductor gas sensors

Different thick-film printing techniques have been used for the fabrication of one-electrode semiconductor gas sensors in the form of thick films on insulating alumina substrate. In a typical one-electrode sensor construction, a thin platinum wire (diameter 20 μm) spiral is embedded inside a sintered oxide semiconductor button. The platinum wire spiral is replaced by a platinum thick-film resistor in our prototype sensor, and the oxide semiconductor is screen printed over the platinum resistor. Both screen printing and gravure off-set printing (pad printing) were used for the printing of platinum thick-film resistors. Tin dioxide, an n-type semiconductor, was used as the sensing (shunting)_thick-film layer over the platinum resistor, and diferent amounts of either silver or antimony were used as additives in SnO 2. H 2S and CO at different concentrations in synthetic air were used to test the response properties of two different sensor types with, respectively, screen-printed and pad-printed platinum thick-film resistors.

Printed microelectrode array and amperometric sensor for environmental monitoring

A disposable electrochemical sensor for the determination of heavy metal traces has been designed for environmental field analysis. The sensor is supported on a polycarbonate film and consist of an amperometric transducer in combination with an adjacent silver-ink reference electrode. The transducer itself is composed of a network of carbon disc microelectrodes. This array of microelectrodes covers a sensing area of 5 × 5 mm and is made up of some 1000–3000 electrodes. Individual disc microelectrodes measuring 15 μm diameter, have a recessed geometry with hole depth of less than 10 μm and centre-to-centre separation between 100 and 300 μm. A novel three-stage fabrication process based on conventional thick-film printing techniques, vacuum polymerisation of a dielectric and a uv excimer laser photoablation process was used to pattern the disc array structure. This microfabrication method has been evaluated on a laboratory scale and batch production. Amperometric performance and structural characteristics of the electrochemical sensor have been examined by chronoamperometry and electron microscopy. Variations in the sensor current response were studied in order to reduce the diffusion shielding characteristics of individual discs. An optimal microelectrode spacing was assigned to the sensor of 160 μm giving more than one thousand discs per device. The printed sensor is currently under development for single-use field measurements of heavy metals using potentiometric stripping analysis.

A novel thick-film technique, gravure offset printing, for the realization of fine-line sensor structures

Gravure offset printing is a novel thick-film printing technique which offers the possibility of printing conductor lines that are narrow compared with those obtained by screen-printing technology. Therefore by using gravure offset printing, denser electronic packaging and sensor structures are feasible. This paper reports the line width and thickness of conductors on alumina substrates produced by the gravure offset technique. As an application example, a multilayer pressure sensor structure consisting of 64 sensors, each 2×2 mm 2 in size, in a matrix is described. This structure is composed of two electrode layers with a piezoceramic layer between them. The narrowest line width of the electrodes is 50 μm. One of the most important benefits of this technique is that it offers the possibility of three-dimensional printing.

The application of excimer laser micromachining for the fabrication of disc microelectrodes

A method is presented for the fabrication of carbon ink microelectrodes in a composite membrane or thin laminate arrangement. The scheme utilises uv excimer laser photoablation of nanosecond pulse duration at wavelength 248nm to generate the required micro-hole stucture in 12 μm PET film. At laser fluences of the order of 1.0 mJ cm −2, film ablation rates were controlled to 0.4 μm per pulse without thermal deformation of the micro-hole. From a micro-hole template a thick film printing technique is used to produce carbon ink microelectrodes with an inlaid disc geometry. A series of microelectrode devices were constructed by this process with disc diameters ranging from 38 μm down to 7 μm with fabrication precision to 1 μm. The amperometric response of the film based microelectrodes were characterized using standard electrochemical measurements and examined by SEM and optical microscopy. Applications are proposed for the new device in the assembly of electrochemical transducers for environmental or clinical sensors.

High-performance plasma display panel with cathodes in the cell walls

An improved color DC plasma display structure was developed and its characteristics were investigated. The configuration of the device is formed using a multiple thick-film printing technique which allows the realization of a large-scale panel. Discharge occurs from thick cathodes formed on three of the cell sidewalls. The panel developed exhibits the following improvements when compared to a conventional panel with straight row-and-column electrodes: it generates a high luminous efficiency of 0.16 lm/W (a 1.3-fold improvement with a 200- mu A/cell), produces high uniformity in light output (a 1.4-fold improvement), and has an increased lifetime under accelerated conditions of 240 h at 400 mu A/cell (corresponding to a 4-fold improvement at 70% of initial brightness). The mechanisms of the improvements used in the new cathode structure are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Planar pulse discharge panel for a TV display

To realize a flat display panel for a high-definition TV (HDTV) receiver, the feasibility of a planar gas-discharge panel simply arranged with both the display and auxiliary cells on the same plane in the panel structure was studied. This would allow for a thick-film printing technique to be used for all fabrication processes. Using a pulse discharge driving scheme to provide internal memory, a monochrome current TV picture with 256 gray levels was reproduced on a small panel with 72 × 100 cells (horizontal cell pitch: 0.7 mm, vertical cell pitch: 0.5 mm).

A Piezoelectric Fan Using PZT Ceramics

A fan consisting of a piezoelectric bimorph tipped with an additional flexible blade is introduced. Since the flexible blade resonates in a large amplitude but the bimorph vibrates in a very small amplitude, the fan can supply sufficient and constant air flow without any structural destruction for a long time. The fan case has two air outlets which are directed oppositely each other. The fan with such outlets can supply an air flow of 4 m3/hr at an applied voltage of 140 Vp–p. Another type of a piezoelectric fan using multi-layered PZT ceramic elements produced by a thick film printing technique is introduced. This fan is suitable for low voltage operation and it can supply an air flow of 1 m3/hr at an applied voltage of 17Vp–p.

Thick-film fabrication techniques for millimetre-wave dielectric waveguide integrated circuits

The letter presents the results of an initial study performed in the development of millimetre-wave dielectric waveguide integrated circuits using novel thick-film printing techniques. The measurements of the propagation characteristics of sample lines at 60 GHz demonstrate the feasibility of such an approach and examples of printed components indicate its potential in low-cost high-volume applications.