The effect of the echo-time of a bipolar pulse waveform on molten metallic droplet formation by squeeze mode piezoelectric inkjet printing

2015 ◽  
Vol 55 (3-4) ◽  
pp. 630-636 ◽  
Author(s):  
Cheng-Han Wu ◽  
Weng-Sing Hwang
Keyword(s):  
Inkjet Printing ◽  
Droplet Formation ◽  
Pulse Waveform ◽  
Bipolar Pulse ◽  
Metallic Droplet ◽  
Echo Time

Ligament Flows of Exit-Pinching During Drop-on-Demand Inkjetting of Alginate Solution

2016 ◽  
Author(s):  
Mengyun Zhang ◽  
Changxue Xu
Keyword(s):  
Inkjet Printing ◽  
Formation Process ◽  
Droplet Formation ◽  
Artificial Organs ◽  
Excitation Voltage ◽  
Capillary Effects ◽  
Alginate Solution ◽  
Nozzle Orifice ◽  
Organ Printing ◽  
Flow Directions

Organ printing is an emerging technology for fabricating artificial tissues and organs, which are constructed layer by layer by precisely placing tissue spheroids or filaments as building blocks. These fabricated artificial organs offers a great potential as alternatives to replace the damaged human organs, providing a promising solution to solve organ donor shortage problem. Inkjetting, one of the key technologies in organ printing, has been widely developed for organ printing because of its moderate fabrication cost, good process controllability and scale-up potentials. Droplet formation process as the first step towards inkjetting 3D cellular structures needs to be studied and controlled precisely. This paper focuses on the ligament flow of exit-pinching during droplet formation process of inkjet printing. The ligament flow directions during pinch-off process of inkjet printing of a sodium alginate solution with a concentration of 0.5% (w/v) have been studied. It is found that two different types of flow directions inside a single ligament during pinch-off process may occur. At an excitation voltage of 30 V, the ligament flow has two different directions at the locations near the nozzle orifice and the jet front head: the negative z direction at the location near the nozzle orifice due to the dominant capillary effect, and the positive z direction at the location near the jet front head due to both the fluid inertial and capillary effects. On the contrary, at an excitation voltage of 70 V, the ligament flow directions are the same at the locations near the nozzle orifice and the jet front head: the positive z direction at the location near the nozzle orifice due to the sufficiently large fluid inertial effect, and the same positive z direction at the location near the jet front head due to both the fluid inertial and capillary effects. Two flow directions inside a single ligament benefit single droplet formation without satellite droplets, but the droplet trajectory will be easily affected by the airflow in the laboratory due to the small droplet velocity as well as the droplet deposition accuracy. Single flow direction inside a single ligament usually results in a long ligament due to the large fluid inertia which eventually breaks into several undesirable satellite droplets. The resulting knowledge will be beneficial for better understanding of the ligament pinch-off during droplet formation process of inkjet printing biological viscoelastic alginate bioink for 3D cellular structure fabrication as well as precise droplet controllability for good quality of fabricated 3D structures.

Control of droplet formation by operating waveform for inks with various viscosities in piezoelectric inkjet printing

2013 ◽  
Vol 111 (2) ◽  
pp. 509-516 ◽  
Author(s):  
Yu-Feng Liu ◽  
Ming-Hsu Tsai ◽  
Yen-Fang Pai ◽  
Weng-Sing Hwang
Keyword(s):  
Inkjet Printing ◽  
Droplet Formation

The effects of coil–stretch transition behavior of polyfluorene inks on single droplet formation during inkjet printing

2020 ◽  
Vol 31 (12) ◽  
pp. 3216-3220
Author(s):  
Zhonghui Du ◽  
Hang Zhou ◽  
Weiran Cao ◽  
Xinhong Yu ◽  
Yanchun Han
Keyword(s):  
Inkjet Printing ◽  
Droplet Formation ◽  
Single Droplet ◽  
Transition Behavior

scholarly journals Simulation study of droplet formation in inkjet printing using ANSYS FLUENT

2022 ◽  
Vol 2161 (1) ◽  
pp. 012026
Author(s):  
Neha Thakur ◽  
Hari Murthy
Keyword(s):  
Ethylene Glycol ◽  
Simulation Model ◽  
Inkjet Printing ◽  
High Viscosity ◽  
Droplet Formation ◽  
Nozzle Diameter ◽  
Print Quality ◽  
Ansys Fluent ◽  
Low Viscosity ◽  
Inkjet Printer

Abstract Flow simulations of jetting of inkjet drops are presented for water and ethylene glycol. In the inkjet printing process, droplet jetting behaviour is the deciding parameter for print quality. The multiphase volume of fluid (VOF) method is used because the interaction between two phases (air and liquid) is involved in the drop formation process. The commercial inkjet printer has a nozzle diameter of ∼73.2μm. In this work, a simulation model of inkjet printer nozzles with different diameters 40μm, 60μm, and 80μm are developed using ANSYS FLUENT software. It is observed that when water is taken as solvent then the stable droplets are generated at 60μm nozzle diameter till 9μs because of its low viscosity. For higher diameter, the stamen formation is observed. Ethylene glycol stable droplets are achieved at 80μm nozzle diameter till 9μs because of their high viscosity (∼10 times that of water). Along with the droplet formation, the sustainability of the droplet in the air before reaching the substrate is also important. The simulation model is an inexpensive, fast, and flexible alternative to study the ink characteristics of the real-world system without wasting resources.

Simulation of Droplet Formation, Ejection, Spread, and Preliminary Designof Nozzle for Direct Ceramic Inkjet Printing

2007 ◽  
Vol 57 (2) ◽  
pp. 287-297 ◽  
Author(s):  
A. Venumadhav Reddy ◽  
P.K. Rajesh ◽  
P.S.R. Krishna Prasad
Keyword(s):  
Inkjet Printing ◽  
Droplet Formation

scholarly journals The retraction of jetted slender viscoelastic liquid filaments

2021 ◽  
Vol 929 ◽  
Author(s):  
Uddalok Sen ◽  
Charu Datt ◽  
Tim Segers ◽  
Herman Wijshoff ◽  
Jacco H. Snoeijer ◽  
...  
Keyword(s):  
Inkjet Printing ◽  
Polymer Concentration ◽  
Droplet Formation ◽  
Deborah Number ◽  
Upper And Lower Bounds ◽  
Satellite Droplet ◽  
Primary Droplet ◽  
The Stability

Long and slender liquid filaments are produced during inkjet printing, which can subsequently either retract to form a single droplet, or break up to form a primary droplet and one or more satellite droplets. These satellite droplets are undesirable since they degrade the quality and reproducibility of the print, and lead to contamination within the enclosure of the print device. Existing strategies for the suppression of satellite droplet formation include, among others, adding viscoelasticity to the ink. In the present work, we aim to improve the understanding of the role of viscoelasticity in suppressing satellite droplets in inkjet printing. We demonstrate that very dilute viscoelastic aqueous solutions ( $\text {concentrations} \sim 0.003\,\%$  wt. polyethylene oxide, corresponding to nozzle Deborah number $De_{n}\sim 3$ ) can suppress satellite droplet formation. Furthermore, we show that, for a given driving condition, upper and lower bounds of polymer concentration exist, within which satellite droplets are suppressed. Satellite droplets are formed at concentrations below the lower bound, while jetting ceases for concentrations above the upper bound (for fixed driving conditions). Moreover, we observe that, with concentrations in between the two bounds, the filaments retract at velocities larger than the corresponding Taylor–Culick velocity for the Newtonian case. We show that this enhanced retraction velocity can be attributed to the elastic tension due to polymer stretching, which builds up during the initial jetting phase. These results shed some light on the complex interplay between inertia, capillarity and viscoelasticity for retracting liquid filaments, which is important for the stability and quality of inkjet printing of polymer solutions.

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