Investigation of Droplet-Ejection Characteristics for a Piezoelectric Inkjet Printhead

2006 ◽  
Vol 220 (4) ◽  
pp. 435-445 ◽  
Author(s):  
A-S Yang ◽  
C-H Cheng ◽  
C-T Lin
Keyword(s):  
Surface Tension ◽  
Piecewise Linear ◽  
Time Interval ◽  
Force Model ◽  
Ejection Time ◽  
Theoretical Formulation ◽  
Construction Technique ◽  
Droplet Ejection ◽  
Ejection Process ◽  
Inkjet Printhead

Numerical simulations are performed to explore the droplet-ejection process for a piezoelectric inkjet printhead. In the analysis, the theoretical model takes account of a set of three-dimensional, time-dependent conservation equations of mass and momentum, with the incorporation of the continuous surface force model for treating the interfacial surface tension effect. The resultant governing equations are solved using an iterative semi-implicit method for pressure-linked equations consistent algorithm for resolving flow properties. The volume-of-fluid method along with the piecewise linear-interface construction technique is implemented to characterize the behaviour of liquid surface movement. With a typical piezodiaphragm printhead as an illustration case, the time evolution of the gas-liquid interface is calculated for an entire ejection cycle of 164 μs. The predicted droplet shapes throughout the ejection process are compared with microphotographed images for the verification of the present theoretical formulation. The flow and transport phenomena in the stages of the ink ejection and the droplet formation are further examined in detail. In response to design needs, the study is extended to determine the variations of ejection characteristics at different settings of nozzle exit diameter, ejection time interval, surface tension, and viscosity of fluid.

Ejection Process Simulation for a Piezoelectric Microdroplet Generator

2006 ◽  
Vol 128 (6) ◽  
pp. 1144-1152 ◽  
Author(s):  
An-Shik Yang ◽  
Wei-Ming Tsai
Keyword(s):  
Surface Tension ◽  
Flow Behavior ◽  
Piecewise Linear ◽  
Feasibility Studies ◽  
Computer Code ◽  
Droplet Breakup ◽  
Test Fluid ◽  
Ejection Time ◽  
Construction Technique ◽  
Ejection Process

The purpose of this work is to investigate the liquid ejection process of a novel microdroplet generator applying a computational approach. In simulations, the theoretical model is based on the unsteady three-dimensional conservation equations of mass and momentum with the treatment of surface tension effect at the gas-liquid boundary by the continuous surface force scheme. The volume-of-fluid method along with the piecewise linear interface construction technique is implemented to describe the interfacial movements. The time evolution of droplet meniscus shape is predicted and compared to Shield’s microphotographed images for the computer code validation. To explore the practicability of the proposed new microdroplet generator, the flow behavior during the stages of liquid ejection and droplet formation are examined with water as the baseline test fluid for a full ejection cycle of 50μs. In addition, 12 numerical experiments were conducted to determine droplet ejection characteristics by systematically varying the ejection time period as well as surface tension and viscosity of liquids. Simulations reveal that a liquid strand with a shorter breakup time and a longer breakup length could be achieved by reducing the ejection time and decreasing the liquid surface tension and viscosity. For the ejection time greater than 4.0μs, the ejection velocity is too low to render a sufficient momentum for droplet breakup. The feasibility studies have demonstrated the potential of this proposed microdroplet generator in dispensing diverse liquids with the surface tension and the viscosity up to 0.08N∕m and 3.0cps.

Numerical Simulation of Droplet Ejection Based on VOF Method

2014 ◽  
Vol 548-549 ◽  
pp. 1257-1264 ◽  
Author(s):  
Xiao Yong Suo
Keyword(s):  
Numerical Simulation ◽  
Surface Tension ◽  
Numerical Model ◽  
Physical Properties ◽  
Vof Method ◽  
Numerical Results ◽  
Droplet Ejection ◽  
Ejection Process ◽  
Ink Jet ◽  
Jet Nozzle

Taking ejection process of the ink droplets from ink-jet nozzle as the prototype, a similar numerical model of droplet ejection was established. The VOF method was applied to track the interface of droplet ejection process and it is shown that the numerical results simulated by the VOF method were accurate and reliable. Six kinds of liquid with different physical properties were chosen as the research object. The numerical results were analyzed and compared. Finally, the effect of the surface tension, viscosity and density on the droplet ejection process was discussed.

Surface Tension Capability Within an Adaptively Refined Compressible Flow Code

2017 ◽  
Author(s):  
Z. Jibben ◽  
J. Velechovsky ◽  
T. Masser ◽  
M. Francois
Keyword(s):  
Surface Tension ◽  
Compressible Flow ◽  
Piecewise Linear ◽  
Surface Force ◽  
Force Model ◽  
Material Interface ◽  
Flow Solver ◽  
Interface Reconstruction ◽  
Volume Method ◽  
Inviscid Compressible Flow

We present a method to simulate surface tension between immiscible materials within an inviscid compressible flow solver. The material interface is represented using the volume of fluid technique with piecewise-linear interface reconstruction. We employ the continuum surface force model for surface tension, implemented in the context of the MUSCL-Hancock finite volume method for the Euler equations on an adaptively refined Eulerian mesh. We show results for droplet verification test cases.

scholarly journals Electrically charged droplet: case study of a simple generator

2014 ◽  
Vol 92 (10) ◽  
pp. 1203-1207 ◽  
Author(s):  
Martin Brandenbourger ◽  
Stéphane Dorbolo
Keyword(s):  
Surface Tension ◽  
Silicone Oil ◽  
Perfect Conductor ◽  
Charged Droplet ◽  
Ejection Time ◽  
Capillary Length ◽  
Droplet Ejection ◽  
Planar Capacitor ◽  
Electrically Charged

We studied the behavior of a simple apparatus that allows charging droplets by induction. We imposed the following constraints: (i) any liquid should be charged (more precisely whatever its surface tension and therefore whatever its wettability, capillary length, etc.); and (ii) the system is to remain as simple as possible. The design of the device results of a compromise regarding both constraints. The device developed is based on a planar capacitor in which the droplets are generated. The influence of the nature of the liquid (i.e., presence of ions in solution, polarity, surface tension, and conductivity) on the charge induced was measured and was found to be independent of the liquid properties (except for the silicone oil). We deduced that, in the considered configuration, fluids behave like a “perfect conductor” as soon as conductive relaxation time is smaller than the droplet ejection time. Under this condition, the charge has the time to move in the droplet to reach the electrostatic regime.

scholarly journals Modelling of Pore Collapse during Polymer Sintering: Viscoelastic Model with Enclosed Gas

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2182
Author(s):  
Florian Wohlgemuth ◽  
Dirk Lellinger ◽  
Ingo Alig
Keyword(s):  
Surface Tension ◽  
Gas Transport ◽  
Selective Laser Sintering ◽  
Viscoelastic Model ◽  
Polymer Melt ◽  
Gas Diffusion ◽  
Gas Pressure ◽  
Parameter Study ◽  
Time Interval ◽  
Pore Collapse

Frenkel’s model for the late stage of coalescence of viscous particles has been extended to describe pore collapse in a viscoelastic melt during polymer sintering. The shrinkage of a pore in a polymer melt driven by surface tension is extended by taking into account the effects of trapped gas and gas transport out of the pore. Viscoelasticity has been shown to have a considerable impact on the time scale of the coalescence process. In addition, gas diffusion modifies the coalescence dynamics. Based on a parameter study, different regimes for the pore collapse have been identified. At the beginning of pore collapse, surface tension is considerably stronger than gas pressure within the pore. In this time interval (surface-tension-driven regime), the pore shrinks even in the absence of gas diffusion through the matrix. In the absence of gas transport, the shrinkage dynamic slows down and stops when the surface tension balances the gas pressure in the pore. If gas transport out of the pore is possible, surface tension and gas pressure are balanced while the gas pressure slowly decreases (diffusion-controlled regime). The final phase of pore collapse, which occurs when the gas pressure within the pore decreases sufficiently, is controlled again by surface tension. The limitations of the model are discussed. To analyze the interplay between different mechanisms and process steps during selective laser sintering, the respective time scales are compared using experimental data.

scholarly journals Systolic Time Interval (STI) in Hypothyroid Patients Receiving High Dose L-Thyroxine

2020 ◽  
Vol 18 (2) ◽  
Author(s):  
Nurul Aulia Zakaria ◽  
Hafizah Pasi ◽  
Mohammad Arif Shahar
Keyword(s):  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Lv Function ◽  
High Dose ◽  
Time Interval ◽  
Ejection Time ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time ◽  
Significant Increment

Introduction: Systolic Time Interval (STI) is a simple,noninvasive and precise technique to assess left ventricular (LV) function. It measures aortic Pre-Ejection Period (PEP) over Left Ventricular Ejection Time (LVET) from echocardiogram. Thyrotoxicosis will enhance LV function and cause reduction of STI.  This study was perform to measure the changes of STI after administration of high dose L-thyroxine and to determine the correlation between high dose L-thyroxine administration and STI. Materials and Method: A Total of 22 patients were screened. Those with cardiac diseases and high Framingham risk score were excluded. Nine patients were started on high dose L-thyroxine (7x their usual dose) once a week during the month of Ramadan.Thyroid hormones ( T3,T4,TSH)  and STI (PEP/LVET) were measured at baseline and within 24 hrs after high dose L-thyroxine ingestion. Results: All patients have normal thyroid hormones level and normal cardiac function at baseline. The median dose (mcg) of L-thyroxine was 600 (437.5,700) while the median level of fT4 (pmol/L) was 17.43(12.38,20.8). Despite the significant increment of fT4 after Lthyroxine ingestion [baseline 13.21(8.19,14.63) vs high dose 17.43(12.38,22.55) p; 0.011] there was no significant change in STI [baseline 0.3(0.2,0.4) vs high dose 0.28(0.26,0.45) p; 0.513]. There was no correlation found between the dose of Lthyroxine and STI (r=0.244 , p;0.526).  Conclusion: Administration of high dose Lthyroxine did not significantly alter STI despite significant increment of fT4 level unlike the naturally occurring thyrotoxicosis.Therefore ‘exogenous’ administration of high dose L-thyroxine is cardiac safe.

Utility of M-Mode Echocardiography for Early Identification of Infants with Persistent Pulmonary Hypertension of the Newborn

PEDIATRICS ◽  
1981 ◽  
Vol 68 (4) ◽  
pp. 515-525 ◽  
Author(s):  
Lilliam M. Valdes-Cruz ◽  
Golde C. Dudell ◽  
Angelo Ferrara ◽  
Barbara J. Nickles
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Disease ◽  
Early Identification ◽  
Clinical Deterioration ◽  
Persistent Pulmonary Hypertension ◽  
Time Interval ◽  
Ejection Time ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time

The clinical syndrome of persistent pulmonary hypertension of the newborn (PPHN) still carries high mortality in spite of improved neonatal care. The purpose of this prospective study was to assess the utility of M-mode echocardiography for the early identification of infants with PPHN prior to clinical deterioration. Echocardiograms of 51 infants who needed fractional inspiratory oxygen (FIO2) ≥0.25 to maintain adequate Pao2 within 36 hours of life were compared to those of 115 healthy full-term and preterm newborns. Of the 51 infants, ten had elevated systolic time interval ratios of both ventricles simultaneously (ventricular pre-ejection period to ventricular ejection time [RPEP/RVET ≤0.50, LPEP/LVET ≤0.38J]). All of these newbrns had PPHN that was manifest clinically by 11 to 30 hours of age. The echocardiographic findings preceded clinical deterioration by at least one to five hours in all cases. The other 41 infants had clinical courses consistent with uncomplicated pulmonary disease. These data indicate that systolic time interval ratios, although not accurate measures of pulmonary arterial pressure and/or pulmonary vascular resistance, permit early identification of infants with PPHN and separation from others with uncomplicated pulmonary disease.

scholarly journals Pressure response and droplet ejection of a piezoelectric inkjet printhead

1999 ◽  
Vol 41 (2) ◽  
pp. 235-248 ◽  
Author(s):  
Ping-Hei Chen ◽  
Hsin-Yah Peng ◽  
Hsin-Yi Liu ◽  
S.-L. Chang ◽  
T.-I. Wu ◽  
...  
Keyword(s):  
Pressure Response ◽  
Droplet Ejection ◽  
Inkjet Printhead

Laser Induced Nano-Droplet Ejection for the Construction of Nano-Inkjets

2012 ◽  
Author(s):  
Yu Yang ◽  
Vijay M. Sundaram ◽  
Alok Soni ◽  
Sy-Bor Wen
Keyword(s):  
Surface Tension ◽  
Pulse Energy ◽  
Nanosecond Laser ◽  
Continuous Laser ◽  
Fluidic Channel ◽  
Robust Approach ◽  
Power Intensity ◽  
On Demand ◽  
Drop On Demand ◽  
Droplet Ejection

To achieve precise nano-droplet ejection, the existing microscale inkjet module could be scaled down to nanoscale, including both the fluidic channel and the pressure driver. While 2D/3D nanoscale fluidic channels are currently available, a nanoscale pressure driver providing high enough power intensity to overcome surface tension for nano-droplet ejection is still lacking. In this study, laser induced nanoscale confined heating with nano-nozzles are constructed and demonstrated as a simple and robust approach to achieve the required pressure driver. For the heating with continuous laser, micro spray composed with nano-droplets can be induced from the nano-nozzles. For the heating with nanosecond laser of adequate pulse energy, drop-on-demand ejection of droplets with similar diameter as the apertures of the nano-nozzle can be achieved.

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