scholarly journals Controlled droplet discretization and manipulation using membrane displacement traps

Lab on a Chip ◽  
2017 ◽  
Vol 17 (21) ◽  
pp. 3717-3724 ◽  
Author(s):  
S. Padmanabhan ◽  
T. Misteli ◽  
D. L. DeVoe
Keyword(s):  
Droplet Formation ◽  
On Demand ◽  
Membrane Displacement ◽  
Active Trap

Active trap arrays allow on-demand droplet formation, ejection, metering, capture, and merging using a simple membrane-actuated design.

scholarly journals On-demand Ferrofluid Droplet Formation With Non-linear Magnetic Permeability in the Presence of a Non-uniform Magnetic Field

2021 ◽  
Author(s):  
Mohamad Ali Bijarchi ◽  
Mohammad Yaghoobi ◽  
Amirhossein Favakeh ◽  
Mohammad Behshad Shafii
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Uniform Magnetic Field ◽  
Maxwell Equations ◽  
Droplet Diameter ◽  
Droplet Formation ◽  
Bond Number ◽  
On Demand ◽  
Drop On Demand ◽  
The Magnetic Field

Abstract The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field achieved by the larger domain for the boundary condition. The Finite volume method and coupling of level-set and Volume of Fluid methods are used for solving equations. The droplet formation is simulated in a two-dimensional axisymmetric domain. The method of solving fluid and magnetic equations is validated using a benchmark. Then, ferrofluid droplet formation is investigated experimentally and the numerical results are in good agreement with the experimental data. The effect of 12 dimensionless parameters including the ratio of magnetic, gravitational, and surface tension forces, the ratio of the nozzle and magnetic coil dimensions, and ferrofluid to continuous-phase properties ratios are studied. The results showed that by increasing the magnetic Bond number, gravitational Bond number, Ohnesorge number, dimensionless saturation magnetization, initial magnetic susceptibility of ferrofluid, the generated droplet diameter reduces, whereas the formation frequency increases. The same results were observed when decreasing the ferrite core diameter to outer nozzle diameter, density, and viscosity ratios.

Study on Terminal Velocity of Continuously Ejected Micro Inkjet Droplet

2019 ◽  
Author(s):  
Seung-Hwan Kang ◽  
Jong Woo Lim ◽  
San Kim ◽  
Dong Kee Sohn ◽  
Han Seo Ko
Keyword(s):  
Drag Force ◽  
High Speed ◽  
Input Voltage ◽  
Droplet Formation ◽  
Terminal Velocity ◽  
Velocity Curve ◽  
Droplet Velocity ◽  
Velocity Change ◽  
On Demand ◽  
Drop On Demand

Abstract It is important to make the droplet formation in the printable area for a design of an inkjet device. One of the important variables for the inkjet is an ejecting velocity which can be controlled by the inkjet device. When the drop-on-demand inkjet nozzle is used, unless the ejecting velocity exceeds the minimum velocity, the droplet may not be ejected or the nozzle surface can be wet, thus the next droplet formation may fail. On the other hand, if the droplet velocity is too fast, splashing may happen when the drop impacts on a substrate, which makes the undesirable printing error. The falling velocity of the inkjet droplet changes by the drag force of air along the falling distance. Therefore, it is required to estimate the exact ejecting, falling and terminal velocity of the inkjet droplet. We measured the inkjet droplet velocity ejecting from the nozzle of a piezoelectric drop-on-demand inkjet device with a push mode. The nozzle diameter was 70 μm and polyethylene glycol aqueous solution was used as ink. The inkjet droplets were generated within a range of 500 to 10,000 Hz of frequencies at a reference piezoelectric input voltage. The successive inkjet droplets were captured by the high-speed camera with 100,000 fps, then the inkjet droplet velocities were analyzed visually at each falling location. The initial to terminal velocity changes of the droplets were calculated theoretically to be compared with the experimental results according to the diameter of the droplet, the drag coefficient, and the Reynolds number. The general terminal velocity of the droplet is determined by the density and diameter of the droplet. However, this study confirmed that the terminal velocity of the continuously ejected droplets by the drop-on-demand inkjet was determined by the interval of the droplets which depended on the frequency. The inkjet droplet in the low frequency has the long interval that is enough to consider as an independent droplet so that it can follow the terminal velocity curve of the general droplet. However, with increasing the frequency, the inkjet droplets are generated frequently and its interval gets shorter, and then its terminal velocity is relatively high not following the general terminal velocity curve. It is considered that each droplet gets into the wake field of the former droplet so that its drag force can decrease and the velocity can increase. We analyzed the velocity change of the inkjet droplet according to its diameter and frequency based on the experimental and numerical results.

A droplet-based pH regulator in microfluidics

Lab on a Chip ◽  
2014 ◽  
Vol 14 (11) ◽  
pp. 1917-1922 ◽  
Author(s):  
Hongbo Zhou ◽  
Gang Li ◽  
Shuhuai Yao
Keyword(s):  
Droplet Formation ◽  
On Demand ◽  
Demand Control

A stable microenvironment with pH ranging from 3 to 11 is achieved by on-demand control of droplet formation and electrolysis.

Alternating Force Based Drop-on-Demand Microdroplet Formation and Three-Dimensional Deposition

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Long Zhao ◽  
Karen Chang Yan ◽  
Rui Yao ◽  
Feng Lin ◽  
Wei Sun
Keyword(s):  
Process Parameters ◽  
Droplet Diameter ◽  
Three Dimensional ◽  
Inertial Force ◽  
Deposition Process ◽  
Droplet Formation ◽  
Solution Viscosity ◽  
Cell Printing ◽  
On Demand ◽  
Drop On Demand

Drop-on-demand (DOD) microdroplet formation and deposition play an important role in additive manufacturing, particularly in printing of three-dimensional (3D) in vitro biological models for pharmacological and pathological studies, for tissue engineering and regenerative medicine applications, and for building of cell-integrated microfluidic devices. In development of a DOD based microdroplet deposition process for 3D cell printing, the droplet formation, controlled on-demand deposition and at the single-cell level, and most importantly, maintaining the viability and functionality of the cells during and after the printing are all remaining to be challenged. This report presents our recent study on developing a novel DOD based microdroplet deposition process for 3D printing by utilization of an alternating viscous and inertial force jetting (AVIFJ) mechanism. The results include an analysis of droplet formation mechanism, the system configuration, and experimental study of the effects of process parameters on microdroplet formation. Sodium alginate solutions are used for microdroplet formation and deposition. Key process parameters include actuation signal waveforms, nozzle dimensional features, and solution viscosity. Sizes of formed microdroplets are examined by measuring the droplet diameter and velocity. Results show that by utilizing a nozzle at a 45 μm diameter, the size of the formed microdroplets is in the range of 52–72 μm in diameter and 0.4–2.0 m/s in jetting speed, respectively. Reproducibility of the system is also examined and the results show that the deviation of the formed microdroplet diameter and the droplet deposition accuracy is within 6% and 6.2 μm range, respectively. Experimental results demonstrate a high controllability and precision for the developed DOD microdroplet deposition system with a potential for precise cell printing.

Simulation of Droplet Formation and Spread in Direct Ceramic Inkjet Printing

2004 ◽  
Author(s):  
P. Ponnambalam ◽  
P. K. Rajesh ◽  
N. Ramakrishnan ◽  
K. Prakasan
Keyword(s):  
Inkjet Printing ◽  
Volume Fraction ◽  
Droplet Formation ◽  
On Demand ◽  
Self Assembling ◽  
Drop On Demand ◽  
Inkjet Printers ◽  
Ceramic Components ◽  
Wave Forms ◽  
Physical Phenomena

Recently, drop on demand inkjet printers have been used to deposit ceramic containing inks to develop ceramic components for several strategic applications (for sensors, fuel cells and for intelligent inks to be used as self assembling particles to interact with incident wave forms). It seems that the availability of literature with respect to the studies on fluid-structure interaction in a drop on demand inkjet printer is limited, though enough information is available on the preparation of ceramic inks. The design of nozzle for drop on demand inkjet printing involves transient interaction between fluids and structures to eject ink droplets. Study of phenomena that contribute to the droplet formation, ejection and deposition on a substrate for several combination of physical properties of constituents of the ink and the characteristics of actuation mechanism is relevant for understanding and effective utilization of direct ceramic inkjet printing (DCIJP). This paper focuses on the simulation of formation and ejection of a ceramic ink droplet (paraffin wax loaded with different volume fraction of alumina particles) from a reservoir using piezoelectric actuation. The properties of ceramic ink are found in literature and they are used for simulation. Simulations were performed with computational fluid dynamics software (CFD-ACE+) which can solve multi-physiscs problems as encountered in DCIJP. This study gives details of the tight interaction among different physical phenomena that contribute to he droplet formation and ejection process. The results from this study will be useful for the preparation of ceramic inks to achieve desired droplet characteristics.

Study of Droplet Formation Process during Drop-on-Demand Inkjetting of Living Cell-Laden Bioink

Langmuir ◽  
2014 ◽  
Vol 30 (30) ◽  
pp. 9130-9138 ◽  
Author(s):  
Changxue Xu ◽  
Meng Zhang ◽  
Yong Huang ◽  
Amod Ogale ◽  
Jianzhong Fu ◽  
...  
Keyword(s):  
Formation Process ◽  
Living Cell ◽  
Droplet Formation ◽  
On Demand ◽  
Drop On Demand
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