Drop Placement Research Articles

Criteria and methodology for evaluating aerial wildfire suppression

Aircraft are often used to drop suppressants and retardants to assist wildfire containment. Drop effectiveness has rarely been measured due to the difficulties in collecting data from wildfires and running field experiments and the absence of definitions and measures. This paper presents a set of criteria and methodologies for evaluating the effectiveness of aerial suppression drops. These consider drop placement, coverage and effect on fire behaviour. This paper also details drop site and delivery conditions that are required for determining causal factors that influence drop effectiveness and allow drops to be compared. Examples of drop impact evaluations made during experimental fires are used to demonstrate these methodologies. The main methods proposed are based on the analysis of orthorectified airborne infrared imagery of drops, which can be used to measure drop dimensions, proximity to fire perimeter and their effect on fire spread. These evaluations can be used to compare tactics, suppressants and delivery systems and to inform cost–benefit analyses of aerial suppression.

A Quantitative Metric for Pattern Fidelity of Bioprinted Cocultures

This article describes a quantitative metric for coculture pattern fidelity and its use in the assessment of bioprinting systems. Increasingly, bioprinting is used to create in vitro cell and tissue models for the purpose of studying cell behavior and cell-cell interaction. To create meaningful models, a bioprinting system must be able to place cells in biologically relevant patterns with sufficient fidelity. A metric for assessing fidelity would be valuable for tuning experimental processes and parameters within a bioprinting system and for comparing performance between different systems. Toward this end, the "bioprinting fidelity index" (BFI), a metric which rates a bioprinted patterned coculture with a single number based on the proportions of correctly placed cells, is proposed. Additionally, a mathematical model of drop-on-demand printing is introduced, which predicts an upper bound on the BFI based on drop placement statistics. A proof-of-concept study was conducted in which patterned cocultures of D1 and 4T07 cells were produced in two different demonstration patterns. The BFI for the patterned cocultures was calculated and compared to the printing model fidelity prediction. The printing model successfully predicted the best BFI observed in the samples, and the BFI showed quantitatively that post-processing techniques negatively impacted the final fidelity of the samples. The BFI provides a principled method for comparing printing and post-processing methods.

Abstract 3883: Miniaturizing the GloSensor™ cAMP assay for MC4R screening using the Echo® acoustic liquid handler

Abstract As biological assays used for HTS and uHTS are miniaturized, it is critical to maintain assay sensitivity while minimizing reagent volumes and maximizing throughput. The GloSensor™ cAMP Assay provides an extremely sensitive and easy to use, real-time luminescent assay format for the interrogation of over expressed or endogenous GPCRs that signal via changes in the intracellular concentration of cAMP. Tipless, touchless transfers with the Echo® liquid handler eliminate the need for costly disposable tips and greatly simplify assay development efforts. Precise and accurate drop placement eliminates cross-contamination. In this work, we demonstrate optimization of the GloSensor cAMP Assay in low-volume format using a stably transfected HEK293 cell line model expressing the melanocortin 4 receptor (MC4R) and a cAMP-sensing variant of firefly luciferase. We show that the Echo liquid handler is able to titrate small molecule and peptide agonists and antagonists, as well as transfer the GloSensor cAMP Reagent, providing robust assay results that are achieved with significantly reduced volumes of cells and compound. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3883. doi:1538-7445.AM2012-3883

Inkjet Masking for Industrial Solar Cell Processes

Masking by inkjet printing has potential benefits for solar cell manufacturing by improving the conversion efficiency and production yield. In industry and on lab scale it has been shown that there are many applications for inkjet masking to improve the solar cell efficiency. These applications include honeycomb texturisation, selective emitter, plating of front side electrodes and using inkjet masking for low-cost rear-side patterning for backcontact cells. Key success factors for inkjet masking are its small feature size and high flexibility. Furthermore the contact-less print method is in line with the general trend towards thinner wafers to reduce the material costs.However, inkjet technology is initially developed for graphical printing, which has less demanding print reliability criteria. In the photovoltaic (PV) industry one malfunctioning nozzle in the inkjet printing system can result in significant decreased device performance or clear visual defects. Therefore the transition from graphical printing to solar cell production cannot be made without a significant improvement in reliability.In 2011 OTB Solar B.V. started the development of the PiXDRO JETx, a high volume industrial inkjet printing system (up to 2400 wafers/hour) which addresses inkjet masking as a first application. For this application a joint development with Océ Technologies targets to demonstrate an inkjet print reliability and accuracy which meets the standards for solar cell manufacturing. The use of self-diagnosing print heads of Océ, redundant print strategies and the automation from OTB Solar form the basis to combine high reliability with industrial throughput and the printing of fine structures with a drop placement accuracy of 7.5μm 3sigma.

An Enhanced Flexible Color Filter Via Imprint Lithography and Inkjet Deposition Methods

We identify new methods for the roll-to-roll production of flexible color filter arrays (CFA) for electronic displays. Through the use of imprint lithography to define “color wells” we have enabled inkjet deposition as a means to generate CFAs, despite the modest precision attainable with liquid drop placement. In this paper, we outline the imprint lithography process and color well design for template production. The advantage of printing the filter array within a predetermined template is demonstrated, and analysis of their structure and optical properties is presented. CFAs, produced by this technique, provide one means to realize color reflective displays. Application of filters produced by the new process to a 3.8 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">''</sup> color VGA (120 micron sub pixel pitch) E-ink based display platform is discussed.

Inkjet printing ceramics: From drops to solid

Inkjet printing is a powerful microfabrication tool that has been applied to the manufacture of ceramic components. To successfully fabricate ceramic objects a number of conditions must be satisfied concerning fluid properties and drop placement accuracy. It has been proposed that fluids are printable within the bounds 1 < Z < 10 (where Z is the inverse of the Ohnesorge number) and these limits are shown to be consistent with ceramic suspensions delivered by piezoelectric drop-on-demand inkjet printers. The physical processes that occur during drop impact and spreading are reviewed and these are shown to define the minimum feature size attainable for a given printed drop diameter. Finally the defects that can occur during the drying of printed drops are reviewed (coffee staining) and mechanisms and methodologies to reduce this phenomenon are discussed.

Functional fluid jetting performance optimization

Abstract The manufacturing method utilizing digital printing technology offers alternatives to create electronic structures to be used even in microelectronic applications. Material deposition based on digital inkjet technology offers advantages over both traditional mask-etch technologies and other printing methods. Inkjet technology works in an additive manner, reducing material consumption and the amount of created waste. Additionally, the digital nature of the process allows flexible production, e.g., rapid design changes, quick prototyping, and small, customized series. This research paper introduces ink jetting performance optimization utilized in a concept where discrete components and bare silicon chips were integrated in a single module with ink jetted interconnections. Jetting optimization of fluids enhances the droplet placement and volume accuracy that is a critical issue when forming interconnections for dense IC circuits. The overall drop placement error in jet printing is a combination of several error sources such as mechanical, dynamical and material related issues. However, the largest error portion is induced by a single printhead. The printhead related errors can be detected by observing the flight behavior after firing from the printhead nozzle. This paper focuses on optimizing the performance of ejected droplets during flight, i.e., drop formation sequence and minimum flight time variance. The average drop velocities of drops fired from separate printhead nozzles can be used to evaluate the difference in placement on substrate, which in worse case may lead to electrical wiring failures. The performance optimization was done by analyzing the initial state, modeling the drop velocity during flight, optimizing the process parameters to satisfy the model, and accepting the model after verification. Two inks, conductive and dielectric, were evaluated and improvement in placement accuracy was achieved through enhanced uniformity in drop average velocities, a dimensionless number, coefficient of variation was enhanced from 0.051 to 0.040,with conductive ink and from 0.111 to 0.049 with dielectric ink, thus decreasing the velocity related drop placement error.

Imaging Considerations for Single-Pass Print System Design

The interest in single-pass inkjet printing has accelerated due to a number of key advantages over other architectures and technological approaches. These include significant increase in productivity over scanning based printing architectures, ability to print using a wide variety of ink types onto different media at high speeds, and image quality that meets or surpasses equivalent scanning based applications. However, these benefits come with significant system design considerations and challenges. Unlike a scanning printer where image quality is benefited by built-in redundancy, in single-pass printing, you don't get a second chance to make a good first impression. The design of a single-pass system must consider all possible variables that affect drop volume and drop placement. Drop placement is dependent on printhead characteristics like jet straightness, velocity uniformity, and alignment; combined with the accuracy of the substrate handling capability of the driving platform. There are potential ways to reduce such errors by properly architecting the system as a fully integrated unit. Important design considerations like interleave pattern between printing rows and proper spacing between these rows to reduce the overall footprint of the print zone can dramatically reduce these errors and thereby improve image quality. This paper investigates such errors quantitatively, how they correlate to system design and ways to address them in an integrated design approach. A variety of analytic and simulation tools used to understand effects on the single-pass image quality are described. Techniques to benchmark motion quality of a conventional printing press will also be discussed. By using these tools, a successful single-pass system can be designed that achieves target image quality requirements.

Production Digital Fabrication System using the Dimatix Q-Class Printhead

The Q-Class printheads are the newest printheads from Fujifilm Dimatix. Due to their silicon orifice plate, they provide improved drop placement accuracy per cost over earlier printheads. These printheads are capable of jetting fluids with a wide range of drop volumes. A new system for generating patterns for a high volume production masking application was developed using the Q-Class printheads. The accuracy of drop placement, feature definition and the throughput of this system will be disclosed. The architecture of the deposition system, which uses new drive electronics developed by ImTech, Inc. and mechanism developed by Korvis Automation, Inc. will be described. During development many practical implementation challenges were encountered. The most significant of these will be identified along with their solutions.

Approaches to High Speed Inkjet Printing

Inkjet aspires to be the dominant technology in commercial printing. Current and future uses of inkjet in that printing market demand faster print frequencies and higher print speeds to achieve the desired throughput and productivity. Xaar is developing a range of technologies that enable high speed printing and exploring the limits of their suitability in specific applications.One such technology uses recent advances in the exploitation of shared wall technology to enable the development of single cycle nozzle operation for shared wall devices. The elimination of the 3-cycle firing mechanism facilitates a threefold increase in print speed without a trade off in image quality. This print performance is a result of continued understanding of fundamental mechanisms associated with complete drop ejection. Printhead evaluation has shown thermal management, drop placement and reliability can meet the requirements with the new productivities.An alternative technology uses standard printheads stacked together inline, printing in 3-cycle firing mode. For this configuration the print image is split accordingly between the printheads and thus the print speed can be increased by a factor equal to the number of printheads. Printhead stacking has been explored by increasing the stack up to seven printheads on an offset-press. The effectiveness of this configuration is evaluated as a function of firing frequency and substrate feed rate, offering important information that needs to be considered for high frequency integrated system design.

Improvement of image quality in single pass UV inkjet printing

This report introduces factors to improve image quality obtained by single pass inkjet printing with UV ink. As reported at NIP24, this study is made with 600 dpi single pass inkjet printheads, capable of single pass printing at 847 mm/s in 108 mm print swath. In the former study, authors concluded that image quality could be sharper by higher pass speed in case of single pass inkjet printing, since amount of ink flow on a media surface before curing can be restricted. However, it was revealed that fast printing speed could suffer image quality with unevenness of image surface created with thick ink layer. In order to solve the problem, approaches are made from both ink and printhead properties. Firstly, static surface tension of UV ink is lowered from 30 to 22-25 mN/m. It is expected to maintain enough dot gain with smaller drop volume, which makes ink layer thinner. Also, color density of ink has to be enhanced to keep equivalent color range with thinner layer. Secondly, printhead is modified in terms of optimum drop volume range from 5 &#x2013; 19 to 4 &#x2013; 12 pl for modified ink. Also, drop placement accuracy is improved by increasing drop velocity. As a result, thickness of ink layer is reduced from 12.7 microns to less than 9.6 microns on a gloss coat media. As a result, appearance of color images are much improved. It is achieved UV ink named AGORA G1 developed by Agfa Graphics.

Ink Jet Printing Devices and Circuits

AbstractFor several years there have been many efforts to employ ink jet technologies in the fabrication of consumer electronics. The potential of displacing large and expensive pieces of electronic fabrication equipment and processes with seemingly appropriately scaled inexpensive alternatives is attractive. However, of course, the devil is in the details. Feature size, accuracy, registration and materials all have sever impacts on design rules, processing, performance and the types of devices appropriate to the technology. Here we present a look at some of the materials and deposition challenges along with solutions developed at PARC. The discussion will include the defining of printed features &gt;5μm with ±1.5μm drop placement and layer to layer alignment accuracy, the materials characteristics of the generally complex functional fluids of interest required for reliable jetting and device performance. Examples of ink jet fabricated integrated circuits, working displays, imagers and RGB color filters for LCD displays will be shared.

Piezoelectric and Other Drop Ejection Technologies for Drop-On-Demand Inkjet

Drop-on-demand (DOD), or impulse, inkjet has been in practical use as a printing and deposition technology for over thirty years. The popularity and growth of this technology can be attributed to evolutionary improvements in the physics of operation, materials, and ink or fluid chemistry. In addition to traditional desktop printing, DOD inkjet is finding acceptance in the areas of industrial printing and digital fabrication. In general, most applications of DOD inkjet technology have centered on thermal and piezoelectric technology as actuators for drop ejection. However, other types of actuators such as thermal membrane, electrostatic membrane and electrostatic inkjet may provide advantages in a more specific range of applications. Although this paper will focus on piezoelectric actuators, a review of the history, physical principles, and current state of each type of inkjet actuator is presented. Thermal inkjet made DOD technology and color graphics available to millions of users on the desktop as well as many other printing applications. Low cost piezoelectric technology entered the marketplace just prior to the rising wave of digital fabrication and materials deposition applications. The wider materials compatibility has led to broader use of piezoelectric inkjet in industrial applications. The physics of the piezoelectric inkjet drivers and the efficacy of the technology for printing applications are also reviewed. Links are drawn between the deformation modes and the varieties of actuation chamber design. Simple one dimensional acoustic theory can be used to model the propagation of pressure waves induced by piezoelectric actuation. The use of multi-pulse waveforms for the control of drop formation is discussed. Free boundary fluid models describe the interaction of pressure wave energy and surface tension that leads to an ejection of a small volume of fluid. Two-phase fluid models describe the dynamics of drop flight, including the formation of satellites and the consequences of drop size modulation techniques. A model of drop placement accuracy is presented. The techniques and tools of piezoelectric inkjet characterization are reviewed, including advances in imaging techniques and the emerging use of modeling and simulation as a primary tool in an iterative design-simulate-prototype-test printhead development process. These explicit models have allowed the successful development of miniaturized piezoelectric designs fabricated with MEMS techniques, which represent the state-of-the-art and future of piezoelectric inkjet. Lastly, the paper will view these significant milestones and technological advances in light of how inkjet technology might influence the future.

Establishing Inkjet Printhead Jetting Performance and Tolerances with Overall Printing System Design

Establishing the required specifications for a printhead is a balancing act between jetting performance, physical interfaces of the printhead and application requirements for building a quality printer. Selecting tolerances impacts printhead cost and system cost. This paper will review the tolerance and performance specification and metrics of the Dimatix Sapphire printhead, analyze drop placement errors as a function of these tolerances and examine how tolerances can be balanced to take advantage of the capability of some of the tolerances. Some tolerances can be balanced within the assembly; others can be used to improve overall performance of the printer itself, or to open tolerance requirements on the printer.An example of this is the straightness capability in the cross process direction. The maximum standard deviation of straightness for the Sapphire is 3.5 milliradians. This is the highest value allowed for any given printhead. Overall, however, the distribution of this parameter is very tight for the measured population. Using a Weibull distribution to describe the population, the majority of printheads have a standard deviation better the 2.0. Very good straightness can be balanced with the tolerances on the registration features of the printhead to the frame, which potentially reduces the cost of these features. Other options can be to increase the standoff of the head over the substrate to open up the possibilities for substrates, or to reduce the tolerances for the media handling.

Positional Accuracy for Ink Jet Deposition in Digital Fabrication

Components or systems that rely on ink jet deposition of complex materials for functional reliability may require a very high level of drop placement accuracy. Drop placement accuracy is a function of print head jetting properties and the mechanism controlling the print head position relative to the substrate in both a spatial and temporal sense. This paper will focus on the control and minimization of positional errors to afford the best opportunity for minimal drop placement error from a given print head. Ink jet deposition is a static and dynamic process that depends on mechanical tolerances, changes in position during motion, and predicting position prior to the actual event of drop ejection. Traditional methods for error assessment use positional accuracy and repeatability as the primary measure. The emphasis for this paper will be on the motion control and mechanical error sources that affect these parameters. Methods for measuring and techniques for reducing error along with examples will be presented.

Printing and Patterning of Quantum Dots using Thermal Inkjet Techniques

The merging of traditional non-contact printing methods with recent and rapid advances in the development and synthesis of novel inorganic and organic materials is emerging as an important and versatile research and manufacturing method enabling a wide range of applications. Specifically, the capability to rapidly dispense small, precisely controlled droplets of functional materials with remarkable placement accuracy is accelerating research and discovery in all areas of chemistry, biology, physics and engineering. Furthermore, rapid patterning, accurate drop placement and the sparing usage of costly materials provide an important tool in manufacturing and production. In this paper, we focus on one such application - the use of thermal inkjet printing to deposit and pattern quantum dots. We outline the development and characterization of quantum dot-based inks and discuss the unique challenges that we addressed in fine tuning the ink formulation and chemistry for thermal inkjet deposition. Additionally, we provide an example of how these new quantum dot-based inks and thermal inkjet printing methods can be used to enable new applications.

Understanding of sliding and contact angle results in tilted plate experiments

Tilted plate experimental methodology is studied in order to address misinterpretations and omissions that exist in the literature. The effect of methodology on subsequent sliding angle measurements is quantitatively assessed in two parts. The first part is a comparison of drop placement techniques in the conventional tilted plate method (drops placed on a level surface, then inclined). The second part is a comparison between the conventional tilted plate method and a modified method, in which the drop is placed on a surface that is already inclined. The first part of the study involved water drops placed on alkyl ketene dimmer (AKD) surfaces using a needle from above as well as below the surface (through a hole). For drops placed from below, three different drop locations (with respect to the hole in the surface) are included in the study. It was found that the drop placement technique had a statistically significant impact on sliding angle measurements, and the most consistent and unbiased measurements resulted when the drop was placed from below, with the hole leading (downhill from) the drop. The second part of the study involved water drops on both AKD (high contact angle hysteresis system) and fluorinated silicon (low contact angle hysteresis) surfaces. For either system, it was shown that sliding angles were lower when drops were placed on surfaces that were already inclined. Since the maximum and minimum contact angles were identical between the two experimental methods, the difference in adhesion was due to variation in contact line shape. The results of this study show that errors of 50–60% would result from using conventional tilted plate measurements to predict droplet mobility on fixed, inclined surfaces, such as those found in condensers. The important distinction between repellency (measured by the advancing contact angle) and drop mobility is also discussed. Further, it was observed that the advancing and receding contact angles do not always correspond to the maximum and minimum contact angles observed in a tilted plate experiment.

Robust, Reliable and Repairable Inkjet Print Head with Dynamic Drop Modulation Feedback for Printable Display Applications

With the advent of Liquid Crystal Display (LCD) and Flexible Display (FD) applications, a number of research and development companies have been pursuing mask-free digital inkjet printing processes to keep manufacture simple, low cost and environmentally friendly for instant, color filter pixelization, color filter black matrix application, polyimide coating, ball spacer, liquid crystal dispensing and light guide micro-lens deposition of back light unit and so forth. As a result, the key challenge is to not only control the drop placement accuracy but also provide sufficient drop volume uniformity control and real-time waveform modulation to meet the critical requirements. This paper focuses on the recent developments of a robust, reliable and repairable print head along with Addressable Waveform Trimming Circuit (AWTC) to enable drop placement accuracy and drop volume uniformity over 256 nozzles and 4-inch print width. Also reported is both the print head and the drive feedback system for the case of pixel-by-pixel dispense of red, green and blue Cholesteric Liquid Crystal (ChLC) which has been widely applied to bi-stable reflective display applications.

Drop Placement Error Analysis for Ink Jet Deposition

Most industrial and commercial applications for materials deposition in a digital format call for a high degree of accuracy to satisfy the output requirements. Ink jet deposition has the potential to meet the requirements by delivering a consistent volume at a precise location in time and space. Currently available ink jet print heads employ multiple jets to enhance throughput and either the print head or the substrate is scanned relative to the other to complete the desired coverage. The timing and order of initiating jet channel firing is controlled by electronics and software, however, differences in flight time of the drops from the nozzle exit to the substrate can result in significant drop placement error. The difference in flight time is due to manufacturing tolerances that include channel-to-channel differences in print head geometry, materials, and drive electronics. A set of dimensionless parameters has been developed that describe drop placement error based on theoretical input as well as experimental data. Using a drop ejection visualization system, it is possible to measure drop flight time and other parameters that characterize the jetting behavior under realistic conditions. Theoretical calculations and experimental results for predicting the drop placement error due to the print head will be presented.

Advances in Piezoelectric Ink Jet Micropumps for Precision Deposition Using Silicon Nozzles

Piezoelectric ink jet micropump devices offer the capability to precisely deposit fluids within microscopic structures. Manufacturers of flat panel displays, using light emitting polymers, have employed piezoelectric ink jet micropumps in their fabrication process to accurately and consistently place fluids within the pixel structure of displays. As an integral tool in this manufacturing process, the piezoelectric ink jet micropump must maintain tolerances necessary for adequate fluid placement in the display pixels and provide jetting operability for reliable functioning with a robustness to attain sufficient life. An industry push to increase display pixel resolution, demand for improved jetability of complex fluids, and the requirement for longer ink jet micropump service life has mandated the advancement of new technologies to meet these demands. State-of-the-art MEMS techniques have been developed to fabricate high quality silicon nozzles for these demanding applications. This paper describes how new silicon nozzle technology has been applied to a piezoelectric ink jet micropump to improve drop placement accuracy, jetting operability, and chemical resistance.