Ink Dispersion Research Articles

Robotic Prototyping of Paper-Based Field-Effect Transistors with Rolled-Up Semiconductor Microtubes

In this article, we propose a robotic rapid prototyping technology for fabricating a new type of paper-based field-effect transistors (FETs). Unlike the existing paper-based electronics developed primarily based on the printing of conductive and semiconductive inks on paper substrates, this new prototyping technology integrates single rolled-up semiconductive microtubes into a device with robotically printed electrodes as the semiconductive channel, through robotic micromanipulation techniques. To improve the uniformity of the printed silver (Ag) ink electrodes, we designed a time-shift mechanism to compensate for the nonuniform ink dispersion at the beginning and ending phases of the robotic printing process. In addition, image processing and motion control algorithms were developed to enable automatic transfer of the prefabricated microtube from its hosting silicon wafer to the printed electrodes on a paper substrate. The effectiveness of the proposed technology was verified by fabricating the paper-based FETs with semiconductive zinc oxide (ZnO) microtubes. Preliminary tests on the mobility of the fabricated ZnO FET demonstrated improved performance over the conventional paper-based FETs with printed semiconductive channels.

Aperture Ratio Improvement by Optimizing the Voltage Slope and Reverse Pulse in the Driving Waveform for Electrowetting Displays.

Electrowetting display (EWD) performance is severely affected by ink distribution and charge trapping in pixel cells. Therefore, a multi structural driving waveform is proposed for improving the aperture ratio of EWDs. In this paper, the hysteresis characteristic (capacitance–voltage, C-V) curve of the EWD pixel is tested and analyzed for obtaining the driving voltage value at the inflection point of the driving waveform. In the composition of driving waveform, a voltage slope is designed for preventing ink dispersion and a reverse pulse is designed for releasing the trapped charge which is caused by hysteresis characteristic. Finally, the frequency and the duty cycle of the driving waveform are optimized for the max aperture ratio by a series of testing. The experimental results show that the proposed driving waveform can improve the ink dispersion behavior, and the aperture ratio of the EWD is about 8% higher than the conventional driving waveform. At the same time, the response speed of the driving waveform can satisfy the dynamic display in EWDs, which provides a new idea for the design of the EWD driving scheme.

Inkjet printed graphene as an interconnect for optoelectronic devices

A comparative study of inkjet-printed graphene films (IPGFs) with mechanically exfoliated, highly crystalline graphene platelets have been conducted. Inkjet-printed graphene films were obtained using liquid-phase exfoliation of bulk graphite, while crystalline, residue-free graphene was obtained from highly-oriented-pyrolytic-graphite (HOPG) using mechanical exfoliation through a viscoelastic transfer process. Optical absorption spectroscopy was used to infer the density of platelets in the graphene-based ink dispersion. Temperature-dependent Raman spectroscopy revealed the presence of the defect D-band peak in the IPGFs, which was not observed in the HOPG-based samples at room temperature, confirming the higher crystalline quality of the latter. Full-width-half-maximum (FWHM) of the G-band was measured to be ~ 26.4 cm−1 for IPGFs compared to ~ 18.6 cm−1 for HOPG-based samples. Moreover, the D-band intensity decreased as temperature increased up to 600 °C for IPGFs, suggesting the possibility of annealing effects that may arise at these temperatures to reduce defect densities. In both HOPG-based samples and IPGF patterns, the G-band and G′-band red-shifted with increasing temperature which can be attributed to elongation of the C–C bond due to thermal expansion, resulting in the anharmonic coupling of the phonon modes. Moreover, a power study demonstrated the IPGFs even with printing passes as low as 10 passes, dissipate ~ 1.03 mW of power at 1 V, which was similar to the power dissipated in the HOPG samples (~ 1.05 mW at 1 V) suggesting good adherence of graphene platelets and high conductivity in IPGFs, which suggests that the inks are favorable for use in interconnects for device platforms in printed electronics. A natural follow-on from this work, was the use of the conductive graphene inks as an interconnect in devices, specifically WS2-based photodetectors, where prototype devices were fabricated and characterized that are also discussed here.

Rheological Study of Electrode Ink for a PEMFC: I/C and Solid Content

Facilitating cost reduction and durability improvement of the next-gen PEMFCs requires focused efforts on not only advanced catalyst materials but also optimized electrode design concepts1,2. Currently, the most widely used electrode in a PEMFC is made from ink dispersion consists of catalyst, catalyst support, ionomer, and solvent. Before advancing optimized electrode design, the desired properties of the electrode ink dispersion and its corresponding relationship to catalyst layer need to be studied3. In our previous work, we have used rheological measurements as a tool to study a baseline electrode ink with Pt/C and Nafion ionomer. The strength, tortuosity and structural character of electrode ink were quantitatively and qualitatively characterized by oscillation amplitude sweep and frequency sweep. The flow property of the catalyst inks was measured by viscometry. A coating process was also simulated and its impact on the ink microstructure was investigated as well. With our preliminary results from the oscillatory and viscometry tests, we proposed physical models to describe Pt/C-ionomer agglomerate as the microstructural unit in various water/IPA binary solvents. These collective data also verify a strong correlation between the electrode ink rheology and its resulting microstructure, which allowed us to speculate the Pt/C-ionomer agglomerate structure in the opaque electrode inks. The rheological characterization of electrode ink not only enhances our fundamental understanding of the electrode formation, but also provides valuable information for electrode optimization. Built upon the foundation of our previous work, we employed an improved approach to study ionomer to carbon ratio and solid content in the electrode ink in this work. The main objective is to improve fuel cell performance through optimization of electrode ink. This comprehensive study allows us to understand the adsorption behavior of ionomer onto Pt/C and their impact on the microstructure of Pt/C-ionomer agglomerates. With the assist of rheological data, we were able to identify the optimal ionomer to carbon ratio for this system at different solid content. Our preliminary results showed strong interactive nature between Pt/C, ionomer content, and volume fraction. Key rheological features of the studied inks and their corresponding relationship to the electrode microstructure for performance optimization will be present at the conference. References Kongkanand A and Mathias MF. The priority and chanllenge of high-power performance of low-platinum proton-exchange membrane fuel cells. The journal of physical chemistry letters, 2016, 7, 1127-1137.Banham D and Ye S. Current status and future development of catalsyt materials and catalyst layers for proton exchange membrane fuel cells: an industrial persperctive. 2017, 2, 629-638.Hatzell KB et. al.. Understanding inks for porous-electrode formation. 2017, 5, 20527-20533.

Rheological Study of Micro Porous Layer and Its Effect on Transport Properties in a PEMFC

Technical challenges related to catalyst flooding in a polymer exchange membrane fuel cell (PEMFC) have led to various studies to improve water management through evolutionary gas diffusion layer (GDL) design[1] [2].It has been well established that a GDL consisting of a macro-porous substrate coated with a hydrophobic microporous layer (MPL) has an indispensable role in gas and water transport [3]. However, a fundamental understanding of the MPL role and its optimal composition and structure are still lacking. Currently, the most widely used MPL in a PEMFC is made from ink dispersion that consists of carbon, PTFE, and solvent. Before MPL optimization is possible, the desired properties of the MPL ink dispersion and its interaction with the macro-porous substrate needs to be studied. In this study, we used rheological measurements as an evaluation tool to study a baseline MPL ink with Acetylene Black (AB) and PTFE. Specifically, we performed intensive rheological experiments to study the following three properties of the MPL ink: 1) flow properties, like viscosity, through continuous ramp rate, 2) viscoelastic properties through cyclical sweeping method, and 3) transient properties through recovery and relaxation measurement. Our preliminary results show that the ink stability, size of the primary agglomerate, viscosity, viscoelastic property, and creep recovery are strongly influenced by carbon to PTFE ratio and the weight percentage of the solid content. Built on the foundation of our previous work, we expand our study to include two types of carbon materials, AB and Carbon Nano Tube, three PTFE/Carbon ratios (20%, 30%, and 40%), and two solvent ratios (IPA rich and water rich) in this study. Standard Toray-H-060 substrate with 20% PTFE is used as the baseline macro-porous substrate and the MPL ink is applied directly onto the substrate by rod coating. The GDL is then dried and sintered accordingly. Both ex-situ evaluations, such as surface roughness, hydrophobicity, coating quality, and MPL penetration, and in-situ fuel cell testing are performed to study the effect of MPL on transport and performance under both wet and dry conditions. Our results provide new insights to enhance transport properties in a PEMFC by optimizing the design of MPL ink. Detail experimental results will be presented at the conference.

Comparative Studies on Two-Electrode Symmetric Supercapacitors Based on Polypyrrole:Poly(4-styrenesulfonate) with Different Molecular Weights of Poly(4-styrenesulfonate).

Poly(4-styrenesulfonate)-conducting polymer (PSS-CP) is advantageous for thin-film electrode manufacturing due to its high conductivity, high charge storage, structural stability, and excellent ink dispersion. In this work, comparative studies of two-electrode symmetric supercapacitors using Polypyrrole:Poly(4-styrenesulfonate) (PPy:PSS), with different molecular weights (Mw’s) of Poly(4-styrenesulfonate) (PSS) as the electrodes, were performed. PPy:PSS can be easily prepared using a simple solution process that enables the mass production of thin-film electrodes with improved electrical and electrochemical properties. As-prepared PPy:PSS, with different PSS molecular weights, were assembled into two-electrode supercapacitors based on coin cell structures. It was confirmed that the electrical and electrochemical properties of PPy:PSS were improved with increasing PSS molecular weight. The coin cell, using PPy:PSS with a PSS molecular weight of 1.0 × 106 g/mol, exhibited higher areal capacitance (175.3 mF/cm2), higher volumetric capacitance (584.2 F/cm3), and longer cycling stability (86.3% after 5000 cycles) compared to those of PPy:PSS with PSS molecular weights of 2.0 × 105 and 7.0 × 104 g/mol. This work provides an efficient approach for producing cost-effective and miniaturized supercapacitors with high conductivity and high specific capacitance for practical applications in a variety of electronic devices.

Ink Wash Painting Style Rendering With Physically-based Ink Dispersion Model

This paper presents a real-time rendering method based on the GPU programmable pipeline for rendering the 3D scene in ink wash painting style. The method is divided into main three parts: First, render the ink properties of 3D model by calculating its vertex curvature. Then, cached the ink properties to a paper structure and using an ink dispersion model which is defined by referencing the theory of porous media to simulate the dispersion of ink. Finally, convert the ink properties to the pixel color information and render it to the screen. This method has a better performance than previous methods in visual quality.

New Application of Old Material: Chinese Traditional Ink for Photothermal Therapy of Metastatic Lymph Nodes.

Finding a simple and effective strategy to eliminate tumor metastatic lymph nodes is highly desired in clinical tumor treatment. Herein, we reported a Chinese traditional ink (Hu-ink)-based treatment for photothermal therapy (PTT) of tumor metastatic lymph nodes. By simple dilution, stable Chinese traditional ink dispersion was obtained, which presents excellent photothermal effect because of its high absorption in near-infrared (NIR) region. Meanwhile, as revealed by staining and photoacoustic imaging, Hu-ink could transfer to nearby lymph nodes after directly injected into the primary tumors. Under the guidance of dual-modality mapping, the metastatic sentinel lymph nodes could be subsequently eliminated by NIR irradiation. The good biocompatibility of Hu-ink has also been verified by a series of experiments. Therefore, the Hu-ink-based treatment exhibits great potential for PTT of tumor metastatic lymph nodes in future clinical practice.

PDLA/PLLA ultrafiltration membrane with excellent permeability, rejection and fouling resistance via stereocomplexation

In this work, a feasible and efficient approach was developed to produce Poly(lactic acid (PLA) ultrafiltration membrane with both high permeability and high rejection simultaneously. Poly(L-lactic acid)/Poly(D-lactic acid) (PDLA/PLLA) stereocomplex crystallites were thought to play the critical role different from the traditional pore forming agents or hydrophilic modification. The membrane morphology of the stereocomplex PDLA/PLLA membrane with high porosity and thin skin layer was observed by SEM. The addition of PDLA resulted in the thermodynamic enhancement for phase separation of PLLA casting solution as demonstrated by a rotational rheometer. The PDLA/PLLA stereocomplex crystallization behavior was investigated by DSC and XRD. With increasing the stereocomplex crystallites, the water permeability of PLA membrane significantly increased from ~482L/m2·h to ~3325L/m2h, while with small loss in degree of rejection. Furthermore, the stereocomplex PLA membrane demonstrated the excellent separation efficiency for nano-TiO2 and ink dispersion. Besides, the stereocomplex PLA membrane exhibited outstanding anti-protein fouling properties through the static and dynamic BSA antifouling tests. All results demonstrated that the stereocomplexation can effectively tune the pore size evolution and control the permeability, selectivity and fouling resistance.

Inkjet printing and surface treatment of an optimized polyurethane-based ink formulation as a suitable insulator over silver for contact with aqueous-based fluids in low-voltage applications

An optimized, formulated polyurethane (PU)-based insulating ink, which was inkjet printed and cured as a tri-layer on top of an inkjet-printed and sintered commercial silver ink base metal fused to polyethylene terephthalate substrate, demonstrated a resistivity of >1.2 × 108 Ω cm at a film thickness of 100 μm when exposed to an aqueous saline solution and a voltage differential of <2 V. This insulating property is highly desirable for biofluids-contacting biosensors. Three PU-based insulator ink formulations were made with different levels of ethylene glycol and carboxymethylcellulose additives to improve ink volatility, viscosity, and dispersion properties. Based on the resultant ink properties important to printing, one of these formulations was selected for further evaluation. The effects of the type and extent of surface conditioning involving UV–O3 and/or thermal treatments on print quality and completed insulator functionality are discussed. Print quality is assessed by visual and profilometry measurement.

Experimental and Theoretical Analysis of Ink Dispersion Stability for Polymer Electrolyte Fuel Cell Applications

The aggregate size in fuel cell catalyst inks depends on the type of dispersion medium, particle concentration, and addition of stabilizing agents. In this work, ink stability and particle size of carbon black and carbon black/Nafion dispersions in four non-aqueous media, viz., methanol, ethanol, isopropanol and ethyl acetate are studied. Based on visual inspection, isopropanol is found to be the best medium for dispersion of carbon black inks. To rationalize this observation, a semi-empirical model based on diffusion-limited aggregation was developed to evaluate the rate of particle aggregation and predict the ink stability time for each dispersion medium. The proposed model supports the experimental observation by qualitatively predicting the same relationship between carbon stability and the dispersion media. The model also showed that the dielectric constant of the dispersion medium and the particle zeta potential are primarily responsible for the ink stability. Particle size for the different inks was determined by dynamic light scattering with and without dilution. Experimental results show that Nafion is a strong stabilizing agent, increasing the ink stability and decreasing the particle size of carbon aggregates. The beneficial effects of Nafion are independent of its concentration and are observed even at Nafion volume fractions of 10 wt%. The interaction energy is found to be a strong function of the surface potential for the dispersion medium with a higher dielectric constant.

Data-Driven NPR Illustrations of Natural Flows in Chinese Painting.

Introducing motion into existing static paintings is becoming a field that is gaining momentum. This effort facilitates keeping artworks current and translating them to different forms for diverse audiences. Chinese ink paintings and Japanese Sumies are well recognized in Western cultures, yet not easily practiced due to the years of training required. We are motivated to develop an interactive system for artists, non-artists, Asians, and non-Asians to enjoy the unique style of Chinese paintings. In this paper, our focus is on replacing static water flow scenes with animations. We include flow patterns, surface ripples, and water wakes which are challenging not only artistically but also algorithmically. We develop a data-driven system that procedurally computes a flow field based on stroke properties extracted from the painting, and animate water flows artistically and stylishly. Technically, our system first extracts water-flow-portraying strokes using their locations, oscillation frequencies, brush patterns, and ink densities. We construct an initial flow pattern by analyzing stroke structures, ink dispersion densities, and placement densities. We cluster extracted strokes as stroke pattern groups to further convey the spirit of the original painting. Then, the system automatically computes a flow field according to the initial flow patterns, water boundaries, and flow obstacles. Finally, our system dynamically generates and animates extracted stroke pattern groups with the constructed field for controllable smoothness and temporal coherence. The users can interactively place the extracted stroke patterns through our adapted Poisson-based composition onto other paintings for water flow animation. In conclusion, our system can visually transform a static Chinese painting to an interactive walk-through with seamless and vivid stroke-based flow animations in its original dynamic spirits without flickering artifacts.

Ink Dispersion on Qianlong Xuan Paper with Improved Ink Expression

Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettability, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.

Suppression of Oxygen Reduction Reaction on Pt-Based Electrocatalysts from Ionomer Interaction

Nafion ionomer is incorporated into cathode catalyst layers of PEMFCs to provide protonic pathways for the ORR reaction. Although it possible to probe the effect of I/C ration in cathode catalyst layers of PEMFCs, the ionomer cannot be completely eliminated. In contrast, when catalysts are evaluated as thin films fabricated on RDE tips and studied in a non-adsorbing electrolyte such as perchloric acid, ionomer is not essential for protonic conduction and can be eliminated. Recently, the effect of Nafion on oxygen reduction reaction (ORR) activity of catalysts has been studied using rotating disk electrode (RDE) methods on single crystalline, polycrystalline Pt surfaces and nanostructured thin film (3M NSTF) in 0.1 M HClO4 [1-5]. In these studies, thin films (nm to 10’s of nm) were applied to the electrode surfaces by capping with ionomer. A positive shift on the onset potential for OH and other oxide species formation and a suppression of the ORR activity is typically observed after capping. Subbaraman et al. [1] attributed the features observed on cyclic voltammograms under inert atmosphere to sulfonate anion adsorption on Pt surfaces using a CO displacement method. Moreover, the activity trend: Pt (111) < (100) < (110) is identical for Nafion-free surfaces in sulfuric acid and Nafion-capped surfaces in perchloric acid solution that led them to conclude that sulfonate anion adsorption was the main cause for lowered ORR activity. In contrast to these detailed kinetics studies on well-defined Pt surfaces, little work has been reported on carbon supported nanoparticle platinum (Pt/C) catalysts [6]. The lack of studies is a consequence of following barriers: (i) ionomer inclusion in a catalyst ink often helps to increase ink dispersion (ii) elimination of ionomer can result in poor catalyst film quality (iii) ionomer is often used for adhesion of catalysts films on substrate surfaces [7]. However, we have recently discovered that the use of extremely thin and uniform films is indispensable to the kinetics study of ORR catalysts without hindrance from O2 diffusion limitations within the catalyst layer and ionomer is not essential to obtain well-dispersed stable thin catalyst films [8]. In this work, we present results on the effect of Nafion ionomer on the ORR activity as well as CVs under inert atmosphere for several commercial Pt/C and Pt Alloy/C catalysts by employing thin-uniform catalyst films obtained by advanced film fabrication techniques [8]. Nafion capped catalyst films were obtained by impregnating diluted Nafion solution onto pre-formed Nafion-free ultra-thin films. The sensitivity of the specific activity of various catalysts including Pt/HSC, Pt/Vulcan, PtxCo1-x/C at 0.9 V vs. RHE in 0.1 M HClO4 to the ionomer to carbon (I/C) ratio will be discussed.

Scalable nanomanufacturing of surfactant-free carbon nanotube inks for spray coatings with high conductivity

Spray-coated carbon nanotube films offer a simple and printable solution for fabricating low cost, lightweight, and flexible thin-film electronics. However, current nanotube spray inks require either a disruptive surfactant or destructive surface functionalization to stabilize dispersions at the cost of the electrical properties of the deposited film. We demonstrate that high-purity few-walled carbon nanotubes may be stabilized in isopropanol after surface functionalization and that optimizing the ink stability dramatically enhances the conductivity of subsequent spray-coated thin films. We consequently report a surfactant-free carbon nanotube ink for spray-coated thin films with conductivities reaching 2,100 S/cm. Zeta-potential measurements, used to quantify the nanotube ink dispersion quality, directly demonstrate a positive correlation with the spraycoated film conductivity, which is the key metric for high-performance printed electronics.

Benchmarking ORR Activity of Pt-Alloy/C Electrocatalysts Utilizing Improved TF-Rde Methods

Thin-film rotating disk electrode (TF-RDE) measurements have been performed to screen the Oxygen Reduction Reaction (ORR) activity of electrocatalysts for PEMFC applications. Through progressive refinement of the technique by several researchers, a number of factors that play a critical role -on measured ORR activity -have been recently reported. Some of the factors include catalyst loading (electrode thickness), film uniformity (spin coating), Nafion cap thickness, ink dispersion/formulation, corrections for iR and background currents, etc. However, for most of these studies, Nafion was typically employed either to improve the catalyst ink dispersion or to glue catalysts on a glassy carbon substrate.In our previous study, we verified the effect of Nafion on the ORR activity as a function of I/C ratio. The measured activity enhancement was reported ~1.8 times for a Pt/HSC catalyst when Nafion was completely eliminated. Further studies demonstrated that the activity could be further enhanced (~2.7 times compared to a Nafion-based catalyst layer) for extremely thin, uniform films that were Nafion-free. The thin films of low Pt loading were prepared either by incorporation of a surfactant in the dispersion or by drying of the electrodes under controlled conditions.While relative standard deviation (RSD; based on ~30 samples for each method) for Nafion based catalyst films ranged ~9–15%, RSD for Nafion-free thin, uniform films was ~6%. This clearly demonstrates high reproducibility of measured ORR activity with the Nafion-free thin, uniform films. Although the reason of the increase has not been elucidated yet, O2 transport and proton transport resistances within the catalyst layer are the most probable causes. Comparison of Tafel plots for Nafion-free and Nafion-based films to a polycrystalline Pt electrode provides some insight into the mechanism. Definitive anion adsorption features of Nafion ionomer were not observable for the Pt/C catalysts in our studies. Although further study is necessary to identify the cause of the large increase, the use of thin films without Nafion seems justified to reduce O2 transport and proton transport resistance within the catalyst layer.In this work, we have studied the ORR activity for various commercially available Pt based alloy catalysts to provide improved baselines using our new techniques. Figure 1 is a plot comparing the ORR activity of baseline Pt/C to PtCo/C catalysts films deposited by conventional Nafion incorporation method (thick coffee ring structured film) and the Nafion-free method (thin-uniform film).The measured specific activity (Figure 1) for Nafion-free, thin-uniform Pt/C films compared to that for a similar Nafion-based film increased by a factor of ~2.7 and is very similar to the enhancements observed for PtCo/C films. Additionally, the specific activity enhancements due to alloying with Co are similar for Nafion-based and Nafion-free films.

Mechanical Modeling of Indigo's Printing Machine Parts

We develop methods to predict printing machines components behavior in order to reduce cost, shorten production time, and to improve lifespan and print quality. These methods of optimization are based on finite element calculations using Abaqus program. Specifically, we model HP-Indigo's machine units, such as the printing blanket, an ink dispersion unit seal and a substrate coating unit. For each component we first characterize the materials by off-line measurements and propose appropriate material descriptions. Then the system is analyzed and dependence of its behavior on relevant parameters is found. This allows for optimization and proposing future configurations, where expensive and time consuming prototypes can be built and tested only for most preferable candidates. These methods are very interesting for a wide range of applications.

Aerosol jet printing of two component thick film resistors on LTCC

Aerosol jet printing is a rather new technology for the deposition of thick film structures offering high line and space resolution. This offers a high potential for miniaturization for thick film structures. The advantages of this technology could be shown with inks carrying single solid powder (e.g. silver, platinum, ceramic or glass powder). Challenging is printing of solid powder mixtures due to the differences in the aerodynamic properties of different powders. Those differences result in changes of the mixing ratio within the aerosol jet and therefore poor reproducibility in the final film properties is obtained. In this work, thick film resistors consisting of RuO2 with particle size &amp;lt; 1 μm as the conducting phase and different glass powders with particle size around 1 μm as the isolating phase were investigated. One glass had a density rather close to RuO2, the other glass significantly lower. Inks were made from RuO2/glass powder mixtures, a solvent and organic additives. After manufacturing the inks are printed on LTCC and the microstructures of the dried and the fired films were visualized by FIB preparation and SEM. The resistances as well as the temperature coefficients of the resistors were measured and compared to resistor films with an identical solid composition manufactured by conventional screen printing. The results of the obtained resistors are presented and discussed in terms of powder properties, ink dispersion and printing parameters.

Intravitreal drug dispersion and needle gauge

AbstractPurpose Intravitreal injections (IV) have become the main treatment for many ocular diseases.. At present, IV are supplied with a 27G, 30G needles. Reduced ocular discomfort and scleral penetration forces have been reported after using smaller gauge needles. However, smaller inner diameter implies increased fluid speed and intraocular turbulence that may result in retinal harmMethods IV were injected with 0.05 mL Indian ink using 27, 30 and 32 G needles. After the injection the eyes were divided in groups and the vitreous was photographed. Three masked observers scored Indian ink dispersion within the vitreous gel from 1 (completely localized) to 4 (complete dispersion).Results Intra‐observer and inter‐observer reproducibility was between 0.78 and 0.95 and between 0.93 and 0.95, respectively (intra‐class correlation coefficient). The average Indian ink dispersion scores for 27, 30 and 32 G needles were 3.4, 2.5 and 1.8 respectively (p=0.07 for 27 vs. 32 G; p= 0.71 for 27G vs. 30G; p=0.15 for 30G vs. 32G; Student t test for unpaired data)Conclusion The inner flow is four times faster in thinner needles, considering that the plunger slides with similar speed. We might expect that flow through the thinner needle would induce more turbulence within the vitreous gel; however, the pattern of intravitreal distribution of Indian ink suggests that the injected fluid and the turbulence were confined to a small bag in the area where smaller gauges were used. The results of this work suggest that 32G needles do not increase turbulence of injected fluid. Limited turbulence may be of even greater interest in elderly eyes with liquefied vitreous gel, reducing mechanical retinal damage

Intravitreal drug dispersion and needle gauge

Purpose Intravitreal injections (IV) have become the main treatment for many ocular diseases.. At present, IV are supplied with a 27G, 30G needles. Reduced ocular discomfort and scleral penetration forces have been reported after using smaller gauge needles. However, smaller inner diameter implies increased fluid speed and intraocular turbulence that may result in retinal harm Methods IV were injected with 0.05 mL Indian ink using 27, 30 and 32 G needles. After the injection the eyes were divided in groups and the vitreous was photographed. Three masked observers scored Indian ink dispersion within the vitreous gel from 1 (completely localized) to 4 (complete dispersion). Results Intra-observer and inter-observer reproducibility was between 0.78 and 0.95 and between 0.93 and 0.95, respectively (intra-class correlation coefficient). The average Indian ink dispersion scores for 27, 30 and 32 G needles were 3.4, 2.5 and 1.8 respectively (p=0.07 for 27 vs. 32 G; p= 0.71 for 27G vs. 30G; p=0.15 for 30G vs. 32G; Student t test for unpaired data) Conclusion The inner flow is four times faster in thinner needles, considering that the plunger slides with similar speed. We might expect that flow through the thinner needle would induce more turbulence within the vitreous gel; however, the pattern of intravitreal distribution of Indian ink suggests that the injected fluid and the turbulence were confined to a small bag in the area where smaller gauges were used. The results of this work suggest that 32G needles do not increase turbulence of injected fluid. Limited turbulence may be of even greater interest in elderly eyes with liquefied vitreous gel, reducing mechanical retinal damage