Papers by Keyword: Inkjet Printing

Abstract: Due to the challenging dispersion of graphene in aqueous media, organic solvents are commonly used in conductive graphene inks. This will result in safety issues and environmental pollution. In this study, we demonstrated a green approach of graphene ink preparation through one-pot synthesis reaction that produce a hybrid reduced graphene oxide (rGO)-silver nanoparticles (AgNPs), with deionized water as solvent. The synthesized rGO-AgNPs was monitored using ultraviolet–visible (UV-Vis) spectroscopy and fourier transform infrared (FTIR). A stable dispersion of rGO-AgNPs ink was confirmed through UV-Vis analysis. FTIR result showed the removal and the reduction in the intensities of absorption bands of oxygen-containing functional groups, which indicated that graphene oxide (GO) has been successfully reduced to rGO in the hybrid ink. The printed film of rGO-AgNPs exhibited a high conductivity of 1.50 × 10⁴ S/cm, proven that the electrical performance of the hybrid ink has been improved as compared to previously reported GO-based ink. Printed into interdigitated electrode (IDE), the impressive characteristic of our hybrid ink performed well as a high-sensitivity flexible humidity sensor.

Abstract: Compared with current methods, additive manufacturing processes could offer a more environment-friendly and cost-effective solution in producing long lasting RFID tags for identification and sensing applications. In this work we report the fabrication of UHF RFID antennas by inkjet printing on a flexible substrate. Silver and gold were chosen as ink materials since they are more resistant to weathering than other metals, particularly for applications that require long-term reusability. We compared the print performance of a commercial silver ink and our lab-developed gold nanoparticle (AuNP) ink on polyethylene naphthalate. The printing process for each ink is described using an adopted loop antenna design optimized for 866-868 MHz frequency range. Assembled passive and battery-assisted RFID tags using single-and double-layer sintered, printed antennas coupled with a readable UHF RFID chip showed tolerable detection distances using a commercial compact reader (with short read range specifications). Additionally, we observed a more consistent print behavior and quality, and consequently longer read ranges for the gold antennas (up to 40 cm with battery). Furthermore, the silver antennas oxidized over time resulting in decreased read ranges. Overall, our results show the viability of a printable gold RFID antenna with a tag working range that may be fit for close range non-contact reading.

Abstract: Inkjet printing (IJP) has emerged as a promising additive manufacturing technique for fabrication of electrodes and sensors due to its cost-effectiveness compared to the traditional techniques, such as screen-printing. In this work, we present a planar, three-electrode system fabricated by inkjet printing on a polyethylene naphthalate (PEN) flexible substrate for rapid voltametric electrochemical analysis. An in-house formulation of aqueous-based gold ink with low temperature-sintering was used in printing the working and counter electrodes. The reference electrode was also inkjet-printed using a commercial silver ink and chlorinated to form an AgCl layer. Cyclic voltammetry studies using the ferri/ferrocyanide redox couple showed that the inkjet-printed electrode system has a comparable electrochemical performance to a commercial screen-printed electrode. Fabrication of a single inkjet-printed electrochemical 3-electrode platform consumes only about 0.5 mg Au and 0.2 mg Ag loading of ink with minimal waste during fabrication because of the additive nature of the printing technique. The 3-electrode platform operates with a microliter sample volume for analysis and can be used in aqueous media without delamination.

Abstract: Although there are currently different applications for gallium in microelectronics, literature is sparse about its applications in the area of conductive inks. The important characteristics to consider from the ink are viscosity, corrosion and surface tension. The importance of viscosity is a critical parameter in the printing ink mixture, which requires a metal to fulfill the function of conductor, such as gold, copper, and silver. Gallium as a conductor replacement is proposed due to the high cost of such metals currently used. The valence electrons are discussed in this paper due to the direct relation that has with metal conductivity, to provide a justified analysis about gallium application in conductive ink. The application of gallium could mean a significant change in conductive ink elaboration process. Thus, the aim of this research is to analyze the application of gallium as conductive ink, which is done by a literature review on gallium as a semi-conductor because of his valence electrons. Results about gallium as a potential conductive ink show that there is evidence that gallium shares similar properties as the current of materials conductive inks being adopted. This first literature review has some implications on the potential use of gallium as a conductive ink, requiring further experimental research to better test for conducting efficiency.

Abstract: The crafts such as lacquerware have made unique strides through decorating techniques using gold such as “Makie”, the technique to draw picture by scattering powdered gold, and “Chinkin”, the technique to rub gold into the design engraved by carving knives. In conventional techniques, practical knowledge and ability are essential to produce craft products. Therefore, screen printing which consists of simple processes has been developed. However, screen printing requires a masking plate made of silk or nylon to create patterns for transcribing ink into objects. This paper presents the formation of a decorative film by inkjet printing with gold nanoparticles for crafts such as lacquerware. The proposed method consists of on-demand process, which makes design changeable without masking. The aims are threefold: 1) to establish a sintering process of gold nanoparticles for acrylonitrile butadiene styrene (ABS) and phenol resin substrates used for synthetic resin products; 2) to characterize the sintered gold film; 3) to examine applicability to industry. The major results obtained are as follows: the appearance and the reflectance spectra of the gold nanoparticle film vary with heat conditions; the proper heat conditions which prevent thermal damage to substrates are the temperature of 373 K or below for the ABS resin substrate, and 423 K or below for the phenol resin substrate, respectively; the gold nanoparticle film possessed a good surface integrity without any voids when the sintering temperature is higher than 323 K for 1 h. Moreover, the film had such a high adhesion to substrates that no separation occurred after cross-cut test; the proposed method applied a lacquerware product made of ABS resin, yielding the decorative film

Abstract: Three-dimensional (3D) printing has been playing an important role in diverse areas in medicine. In order to promote the development of tissue engineering, this study attempts to fabricate tissue engineering scaffolds using the inkjet printing technology. Sodium alginate, exhibiting similar properties to the native human extracellular matrix (ECM), was used as bioink. The jetted fluid of sodium alginate would be gelatinized when printed into the calcium chloride solution. The characteristics of the 3D-printed sodium alginate scaffold were systematically measured and analyzed. The results show that, the pore size, porosity and degradation property of these scaffolds could be well controlled. This study indicates the capability of 3D bioprinting technology for preparing tissue engineering scaffolds.

Abstract: Nowadays, flexible electronic is an important technology to produce flexible electronic devices due to it offers the attractive features such as possibility of product types and designs, with reducing size and weight, and low cost. Poly (3,4-ethelenedioxythiophene):poly (stylenesulfonate) (PEDOT:PSS) is a conductive polymer which possess high conductivity, high electrochemical, and low redox potential. PEDOT:PSS and PEDOT:PSS/Graphene (GP)/Dimethyl sulfoxide (DMSO) conductive ink ware deposited on Polyethylene terephthalate (PET) flexible substrate using desktop inkjet printer. Conductivity and thickness of conductive pattern at 1, 3, 5, 10, 20 layers were investigated in this study. It is observed that sheet resistivity of the conductive pattern is influenced by number of printed layers. Addition of GP at 20 layers of PEDOT:PSS/GP/DMSO conductive pattern exhibits the lowest sheet resistivity at 44 ohm/󠇯󠇯sq compared to PEDOT:PSS conductive pattern of 1.81×10⁴ ohm/󠇯󠇯sq.

Abstract: The paper deals with the study of optical and electrical properties of inkjet-printed graphene oxide (GO) layers, which can be used e.g. for the preparation of various types of electronic devices. To ensure stable inkjet printing conditions of GO solution, mixture was thoroughly stirred for 1 h at room temperature or sonicated in the bath for 30 min. The thicknesses of prepared layers were determined by spectroscopic ellipsometry and profilometry. An electrical conductivity of GO was increased by the multistep reduction (due to annealing) – the conductivity was changed by these processes about seven orders of magnitude (GO is an isolator and reduced GO is a conductor). For electrical and dielectric measurements, samples with GO and mixture of GO with PEDOT were prepared. All current-voltage characteristics have a diode character. From AC measurements the bulk electrical conductivity and geometric capacity of prepared layers were determined.

Abstract: Conductive ink for inkjet printing has attracted considerable interest for the preparation of advanced electronic circuits. However, high silver content and multiple printing are necessary in order to acquire better conductivity when using spherical silver nanoparticles. In order to reduce manufacturing cost, triangular silver nanoplates were prepared by modified solvothermal method and used for conductive ink. During sintering process of prtinted patterns, the tips of triangular nanoplates were first melted and turned round for high energy of tips. The resistivity of inkjet printed line is 7.6×10^-6 Ω·cm when using triangular nanoplates ink with 10 percent content, while it is necessary to use more than 15 percent content for spherical nanoparticles. This is because surface contact between nanoplates can provide more paths for electron transmission relative to spherical nanoparticles.

Abstract: Electrohydrodynamic Direct-Writing (EDW) provides a simple and rapid way to print micro/nanostructures from viscoelastic solution, which meets the demand in the development of all-printed organic electronics. Overlapped printing of different functional materials to build up multi-layer devices displays excellent advantages in the flexible electron. The 3D multi-layer devices as well as flat interconnection can be fabricated on the flexible substrate directly via EDW technology. The technology of EDW utilized stable charged jet to print orderly conductive and insulator micro/nanostructure. Silver ink is used to print conductor connection, and polyvinylpyrrolidone (PVP) solution is used to fabricate insulator layer. Multi-layer interconnection can be printed layer by layer on the polyimide (PI) flexible insulator substrate. The resistance of top and bottom conductor connection was 6.1Ω and 5.9Ω, respectively. The insulator layer demonstrated excellent insulation characteristics between the bottom and top silver interconnection.