Inkjet System Research Articles

Long-Reach Flying Functional Inkjet System By Employing Electrostatic Acceleration

Abstract In this paper, the authors proposed a novel idea of a long-reach flying inkjet system employing electrostatically-accelerated ink drop for the purpose of functional ink micro pattern plotting by contact-free and environment friendly. Proposed working principle was demonstrated through experiment and analysis. At the 5-mm of electrode gap and φ 120 μm of nozzle, the applicable maximum voltage was 3.5kV realizing 67% up (1.67 times) of droplet flying velocity by one-step of accelerating. By φ 10 μm of droplet, over 35m/s of flying velocity was promising and by 2~3 steps of acceleratingfurther of speed increment could be expected.

Simulation of droplet generation through electrostatic forces

This paper represents the multiphysics simulation of droplet generation of ink containing conductive nano-particles through electrostatic forces on substrate. The main focus is to investigate the phenomena by generating the drops through a nozzle with the help of electrostatic forces. The electrostatic based deposition system has vast application in printed electronics and biotechnology. In electrostatic deposition mechanism for droplet generation, a strong electric potential is applied at the tip of the nozzle; due this electric potential, the liquid containing the nano-particles experience strong electrostatic static forces at the interface with the air (at the tip of the nozzle). When these electrostatic forces exceed the internal (viscous forces) and external forces (surface tension), a deformation takes place which results in the flow of the liquid in the form of droplets. The size of the droplet is dependent on different parameters like applied voltage, properties of the ink, dimension of the nozzle. To have better understanding of this, a numerical simulation was performed based on multi-physics approach. Multiple simulations were performed by changing the position of electrode in nozzle and varying the applied voltage. Droplet size with respect to applied voltage was evaluated; electric field with respect to applied voltage and time for the droplet generation was also evaluated through these simulations. This study will help in better understanding the parameters of droplet generation phenomena and optimal design of the nozzle for the electrostatic inkjet system.

Print the Printed Circuit Board – Inkjet Printing of Electronic Devices

Inkjet printing of nano particles is a new technology for the manufacturing of Printed Circuit Boards. Inks containing silver, copper or Carbon Nano Tube particles were deposited on various substrates like polyimide, Fr 4, paper or even wood with a special inkjet system as well as with standard office printers. Depending on the ink composition, at temperatures from 150-250 °C sufficient electrical conductivity was achieved. The capability of functional inkjet printing is demonstrated with a FM radio which was printed with silver ink, the components being attached by isotropic conductive glue.

Fabrication of BaTiO3Thin Films and Microdot Patterns by Halide-Free Nonaqueous Solution Route

This paper reports on the fabrication of barium titanate (BaTiO3) thin films using a precursor solution containing Ba and Ti alkoxides. l-proline was used to prevent the precipitation of Ba and Ti alkoxides in a mixed solvent of ethanol and butylcarbitol under ambient conditions. Analysis of X-ray diffraction and Raman spectra revealed that the as-deposited amorphous film crystallized into a tetragonal BaTiO3 phase after annealing at 650°C in air. Scanning electron microscopic observations showed that the BaTiO3 film was free from cracks even after annealing and exhibited good adhesion to the substrate. Because the precursor solution developed was sufficiently stable in air, dot patterning of BaTiO3 was also performed using an inkjet system.

Dielectrophoretic deflection of ink jets

In continuous ink jet systems, streams of ∼10 pL liquid droplets (diameter ∼30 µm) are ejected from an orifice at rates of up to 350 000 per second with velocities in excess of 20 m s−1. Applications as diverse as printing, MEMS fabrication and microarraying benefit from this technology; however, reliable manipulation of the jet, including basic on/off control and steering of the liquid droplets, remains difficult to achieve. We report a novel scheme to manipulate the trajectories of droplets that rebound at shallow angles from a solid substrate using the dielectrophoretic force exerted by patterned electrodes. Varying the voltage applied to the electrodes provides precise control of the rebounding trajectories, mainly by shifting the location of the droplet impact. This technique can also be used to implement on/off control of the droplet stream. A simple dynamic model successfully predicts the modified trajectories of the droplets.

A Modified Consumer Inkjet for Spatiotemporal Control of Gene Expression

This paper presents a low-cost inkjet dosing system capable of continuous, two-dimensional spatiotemporal regulation of gene expression via delivery of diffusible regulators to a custom-mounted gel culture of E. coli. A consumer-grade, inkjet printer was adapted for chemical printing; E. coli cultures were grown on 750 µm thick agar embedded in micro-wells machined into commercial compact discs. Spatio-temporal regulation of the lac operon was demonstrated via the printing of patterns of lactose and glucose directly into the cultures; X-Gal blue patterns were used for visual feedback. We demonstrate how the bistable nature of the lac operon's feedback, when perturbed by patterning lactose (inducer) and glucose (inhibitor), can lead to coordination of cell expression patterns across a field in ways that mimic motifs seen in developmental biology. Examples of this include sharp boundaries and the generation of traveling waves of mRNA expression. To our knowledge, this is the first demonstration of reaction-diffusion effects in the well-studied lac operon. A finite element reaction-diffusion model of the lac operon is also presented which predicts pattern formation with good fidelity.

Reduction of droplet volume by controlling actuating waveforms in inkjet printing for micro-pattern formation

Inkjet printing has proven to be a promising and flexible process methodology for low cost and drop-on-demand pattern formation in small-scale production of micro-electro-mechanical systems. To optimize the micro-patterns formed by inkjet printing, an accurate control of droplet volume is essential and critical. In this study, an inkjet system with a nozzle driven by a circular piezoelectric element was used to explore the impact of different waveforms on droplet volume. The investigation into this study included the impact of unipolar, bipolar, M-shaped and W-shaped waveforms as well as the effects of their amplitudes and pulse durations. The inkjetting behavior of Newtonian and non-Newtonian fluids under different actuating waveforms was studied in order to obtain a maximum reduction in ejected droplet sizes. An effective reduction of droplet volume in the range of 50–80% was demonstrated. The results of inkjetting PEDOT ink on a polished silicon surface showed that a 50% reduction in line width was achieved.

Synthesis of submicron sized silver powder for metal deposition via laser sintered inkjet printing

Submicron sized silver powder was prepared from AgNO3 using a chemical-reduction method. A spherical silver power exhibiting an average particle size distribution of 0.2–0.4 μm and an excellent dispersibility was achieved and applied to the inkjet printing process. A drop-on-demand (DOD) inkjetting system was used to print the silver particles suspended in a terpineol solvent. Through sintering at 300 °C, the size of the particles adjacent to the borderline of droplets were gradually increased and necking was observed between the droplets. Alternatively, the substrate for the particles could be heated to a lower temperature, and the sintering process of the conducting line was completed by the application of a laser beam. Increase in the laser power reduces the resistivity of the line. Through microstructure analysis, the necks between droplets were sintered at a specific energy density (ψ = 0.0398 J mm−3). The conducting lines were soldered and of a larger aggregation, between which a discontinuous micro-crack was observed. This was attributed to the surface tension effect and shrinkage during solidification. Influence of the densification parameters on resistivity was significant.

Optimized in situ DNA synthesis on patterned glass

AbstractThis paper describes studies of patterned arrays on glass surfaces and their use as spatially separated reactors for in situ synthesis of DNA using an inkjet synthesizer. Photolithographic methods were employed to fabricate arrays composed of homogenous circular features containing a hydroxyl-terminated silane coupled to the surface of the glass via a siloxane bond. Features are embedded within a background matrix composed of a fluorosilane attached to the glass. Due to the differential wettability of the two silanes, whereby the hydroxyl-terminated silane and fluorosilane are hydrophilic and hydrophobic respectively because of their head groups, the patterned circular features are able to constrain liquid within a defined site. The silanization result was analyzed using X-ray photoelectron spectroscopy (XPS) to optimize silanization time and solvent. Synthesis was then performed using a custom-built inkjet system using phosphoramidite chemistry. Base-by-base analysis using fluorescent labeling showed consistent coupling efficiency on synthesis of a 50-mer homopolymer.

A New Trial of Resist Coating by Applying Electro-Statically Extracted Ink-Jet

In this study, an application of electro-statically extracted ink-jet system has been tried on to the new resist coating method. This new method is based on the corpuscles state of flying resist by electro-statically extracted ink-jet. We have learned that the effectiveness of the resist coating by using electro-statically extracted ink-jet was rather reasonable of its specific application.

Quality control of inkjet technology for DNA microarray fabrication

A robust manufacturing process is essential to make high-quality DNA microarrays, especially for use in diagnostic tests. We investigated different failure modes of the inkjet printing process used to manufacture low-density microarrays. A single nozzle inkjet spotter was provided with two optical imaging systems, monitoring in real time the flight path of every droplet. If a droplet emission failure is detected, the printing process is automatically stopped. We analyzed over 1.3 million droplets. This information was used to investigate the performance of the inkjet system and to obtain detailed insight into the frequency and causes of jetting failures. Of all the substrates investigated, 96.2% were produced without any system or jetting failures. In 1.6% of the substrates, droplet emission failed and was correctly identified. Appropriate measures could then be taken to get the process back on track. In 2.2%, the imaging systems failed while droplet emission occurred correctly. In 0.1% of the substrates, droplet emission failure that was not timely detected occurred. Thus, the overall yield of the microarray manufacturing process was 99.9%, which is highly acceptable for prototyping.

UV nanoimprint lithography process optimization for electron device manufacturing on nanosized scale

Imprint specific process parameters like the residual layer thickness and the etch resistance of the UV polymers for the substrate etch process have to be optimized to introduce UV nanoimprint lithography (UV NIL) as a high-resolution, low-cost patterning technique for research and industry into electron device manufacturing. Additionally, UV NIL processes have to be compatible with conventional silicon (Si) semiconductor processing. Within this work, the minimization of the residual layer thickness by using a multi-drop ink-jet system, which was integrated into the imprint stepper NPS300 from S-E-T-(formerly SUSS MicroTec), in combination with a low viscous UV polymer from Asahi Glass Company is shown. The etch resistance of different UV polymers against the poly-Si etch process was increased by 50% with an appropriate post-exposure bake. A poly-Si dry etch process was used to pattern the gates of short channel MOSFETs. After optimizing the poly-Si etch, properly working short channel MOSFETs with a minimum gate length of about 90 nm were fabricated demonstrating successfully the compatibility of UV NIL with conventional Si semiconductor processing on nanosized scale.

Fast patterning microstructures using inkjet printing conformal masks

The presented paper describes a novel process using inkjet printing to pattern a conformal (built-on) mask onto photoresist for further microstructure formation. The advantages of using the inkjet printing conformal mask include no Cr photomask required, suitable for non-planar substrate, scalable for large area, and extreme low cost. The ink is ejected from the inkjet print-head controlled by the inkjet system. A CAD pattern from the designer can use this process to place the pattern ink onto the photoresist substrate. A conformal mask (made of ink) was directly built-on the photoresist substrate. The dried ink thickness has to be more than 1.8 μm thick as UV absorber. Following UV exposure, development, and ink removal, the designed microstructure patterns can be realized in photoresist such as microchannels and micro-columns.

Top-Contact Organic Thin-Film Transistors Fabricated by Picoliter and Sub-Femtoliter Inkjets

Employing inkjet technologies with picoliter and sub-femtoliter droplet volumes, we have successfully manufactured high-quality top-contact organic thin-film transistors. Silver fine lines were directly patterned by two inkjet systems on the pentacene channel layer without the need for any photolithographic pre patterning or any surface pretreatment. The lines were calcinated at 130 {degree sign}C to form source and drain electrodes. The minimum width of silver lines was 25 µm with the picoliter inkjet system, while that was 2µm with the sub-femtoliter inkjet system. We have manufactured p-type channel and n-type channel organic transistors with source/drain contacts prepared by the sub-femtoliter inkjet to fabricate complimentary inverter circuits.

Synchrotron radiation microdiffraction of ballistic molten wax microdrops

Using stroboscopic techniques, diffraction patterns of ballistic paraffin wax microdrops have been observed. The microdrops, generated by a high-temperature ink-jet system, travel through the 1 mum synchrotron radiation beam with a speed of about 1.4 m/s. Diffraction patterns were recorded in flight by a charge couple device with a microchannel plate image intensifier stage, which was activated with the microdrop generation frequency of 1000 Hz during 2 mus. The data show liquid microdrops with a constant temperature up to 8 mm from the ink-jet system capillary exit. The general technique could be adapted for studying fast structural processes, such as protein conformational changes in aqueous microdrops.

Modeling and characterization of an industrial inkjet head for micro-patterning on printed circuit boards

A conceptual design using computational fluid dynamics (CFD) and micro-electro-mechanical systems (MEMS) fabrication has been performed to develop an industrial inkjet head for micro-patterning on printed circuit boards. The printhead has been fabricated with silicon and silicon on insulator (SOI) wafers by MEMS process and silicon to silicon bonding method. The measured displacement waveform from a piezoelectric actuator by laser doppler vibrometer (LDV) was used as input data for the three-dimensional flow solver to simulate the droplet formation. The mechanism of droplet ejection from piezoelectric-type inkjet heads was investigated by simulating two-phase flows of the air and metal inks. As a preliminary approach, liquid metal jetting phenomena are identified by simulating droplet ejection and droplet formation in a consequent manner. Parametric studies are followed by the design optimization process to deduce key factors to inkjet head performance: nozzle geometry, droplet size, ejecting speed, pulse amplitude, and ink viscosity. The present design tool, based on a two-phase flow solver and experimental measurements, has shown its promising applicability to various concept designs of industrial inkjet system for micro-patterning on electronic chips and boards.

Gap Adjustable Molten Metal DoD Inkjet System With Cone-Shaped Piston Head

In this paper, we present the design, fabrication, and performance test of a gap adjustable molten metal drop-on-demand (DoD) inkjet system with a cone-shaped piston head, which can eject a droplet of lead-free molten solder at high temperature. The gap adjustable mechanism with the cone-shaped piston head is proposed for optimizing the gap distance between the chamber wall and piston head. The droplet diameter and velocity can be controlled in a wide range by moving the initial gap distance and minutely by controlling the chamber pressure. Stability and satellite can be partly adjusted by controlling the initial gap distance and the chamber pressure, respectively. The working temperature is improved by locating the piezoelectric actuator at the outside of the furnace and by inserting the insulation block between the print head and the actuator. From a practical point of view, the molten metal DoD inkjet system presents a simple structure for easily interchangeable nozzle parts, even though the nozzle is choked. The gap adjustable molten metal DoD inkjet system with cone-shaped piston head has great potential as a manufacturing tool for direct printing a viscous material at various temperatures. It is expected to be applicable in many industrial fields including semiconductor packaging, electrode bonding, printed electronics, information, and display industry.

Effect of an entrained air bubble on the acoustics of an ink channel

Piezo-driven inkjet systems are very sensitive to air entrapment. The entrapped air bubbles grow by rectified diffusion in the ink channel and finally result in nozzle failure. Experimental results on the dynamics of fully grown air bubbles are presented. It is found that the bubble counteracts the pressure buildup necessary for the droplet formation. The channel acoustics and the air bubble dynamics are modeled. For good agreement with the experimental data it is crucial to include the confined geometry into the model: The air bubble acts back on the acoustic field in the channel and thus on its own dynamics. This two-way coupling limits further bubble growth and thus determines the saturation size of the bubble.

Stain Resistance Method Development for Consumer Digital Ink Jet and Thermal Imaging Systems. Part I

Methods for determining overall print permanence or image stability for digital ink jet and thermal photographic prints have been well defined and are used to represent typical long-term, home storage conditions for consumer prints. What these methods do not take into consideration are instances where a consumer might accidentally spill substances onto unprotected prints, resulting in unwanted staining. Typical substances can range from high staining materials such as coffee to lower staining materials such as milk. In these instances, damage caused by unwanted staining could certainly impact the long-term preservation of consumer prints. To date, the only existing international standards for this type of image degradation include an ASTM procedure for stain resistance and an ISO procedure for water resistance. This article will discuss the importance of considering stain resistance as part of long-term image permanence criteria for digital consumer color prints and shortcomings associated with the current international standards. Emphasis will be placed on the rationale and development of a more robust procedure for stain resistance and a final method proposal will be made. In addition, application of the proposed method will be discussed and the results from this for several digital ink jet and thermal imaging systems will be summarized.

Stain Resistance as Part of Image Permanence for Consumer Digital Inkjet and Thermal Imaging Systems - Part 2

Development of a more robust procedure for quantifying unwanted staining of prints caused by accidental spills of common household beverages were presented at the 2007 IS&T Non-Impact Printing Conference. This included a review of methodologies that were currently in the literature plus the pros and cons associated with each. Results from a marketing study that identified categories of top beverages consumed worldwide were described and preliminary results assessing stain severity as a function of beverage were reviewed. Generally speaking, highly colored beverages such as coffee and red fruit punch showed higher levels of staining, and less-colored beverages such as fruit-flavored water or beer exhibited very little staining. What was not expected was the amount of staining observed with a light blue-colored sports energy drink. Although this beverage was not highly colored, the level of staining based on a visual assessment for most media ranged between 0.5 and 2 (where 0 equaled no stain and 5 equaled severe stain). This suggests that stain severity may not be solely related to highly colored beverages. Because of this finding, coupled with the stipulation that beverage brands cannot be cited within an international standard, more work was needed to understand root causes of unwanted staining. This paper will discuss studies implemented to determine whether stain severity can be correlated with factors such as what colorants are present in beverages, and/or the physical and chemical properties such as pH, viscosity, surface tension, and/or conductivity. In addition, preliminary results from a voice-of-the-customer (VOC) study will also be presented to outline what levels of staining would be considered acceptable versus unacceptable.