scholarly journals Droplet Transportation through an Orifice on Electrode for Digital Microfluidics Modulations

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1385
Author(s):  
Ting-Chia Chu ◽  
Yen-Wen Lu
Keyword(s):  
Digital Microfluidics ◽  
Electrical Potential ◽  
Core Shell ◽  
Droplet Deformation ◽  
Electrowetting On Dielectric ◽  
The Core ◽  
Paper Based Microfluidics ◽  
Digital Microfluidic ◽  
Interface Chip

A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core–shell droplets is presented. The electrodes were geometrically designed to promote droplet deformation and suspension. The droplets were then applied with an electrical potential for insertion into and passage through the orifice. The concepts were tested with three types of droplets at the volume of 0.75~1.5 μL, which is usually difficult to transfer through an orifice. The integration of electrowetting on dielectric (EWOD) with paper-based microfluidics was demonstrated: the droplet could be transported within 10 s. More importantly, most of the core droplet (~97%) was extracted and passed through with only minimal shell droplets accompanying it.

scholarly journals Phase separation of multiphase droplets in a digital microfluidic device

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Mun Mun Nahar ◽  
Hyejin Moon
Keyword(s):  
Phase Separation ◽  
Capillary Number ◽  
Digital Microfluidics ◽  
Separation Performance ◽  
Comprehensive Investigation ◽  
Electrowetting On Dielectric ◽  
Splitting Technique ◽  
Droplet Splitting ◽  
Two Phases ◽  
Digital Microfluidic

Abstract This study reports the first comprehensive investigation of separation of the immiscible phases of multiphase droplets in digital microfluidics (DMF) platform. Electrowetting-on-dielectric (EWOD) actuation has been used to mechanically separate the phases. Phase separation performance in terms of percentage residue of one phase into another phase has been quantified. It was conceived that the residue formation can be controlled by controlling the deformation of the phases. The larger capillary number of the neck forming phase is associated with the larger amount of deformation as well as more residue. In this study, we propose two different ways to control the deformation of the phases. In the first method, we applied different EWOD operation voltages on two phases to maintain equal capillary numbers during phase separation. In the second method, while keeping the applied voltages same on both sides, we tested the phase separation performance by varying the actuation schemes. Less than 2% of residue was achieved by both methods, which is almost 90% improvement compared to the phase separation by the conventional droplet splitting technique in EWOD DMF platform, where the residue percentage can go up to 20%.

Numerical Simulation of Multi-Physical Fields Coupling and Design of a Digital Microfluidics Chip

2012 ◽  
Vol 503 ◽  
pp. 359-365 ◽  
Author(s):  
Tao Chen ◽  
Li Guo Chen ◽  
Ming Qiang Pan ◽  
Ming Xiang Ling ◽  
Li Ning Sun
Keyword(s):  
Numerical Simulation ◽  
Electric Field ◽  
Microfluidic Chip ◽  
Stokes Equations ◽  
Driving Forces ◽  
Geometric Model ◽  
Digital Microfluidics ◽  
Electrowetting On Dielectric ◽  
Physical Fields ◽  
Digital Microfluidic

Due to its simple structure, low consumption of energy but strong driving forces, Electrowetting on Dielectric (EWOD) is used most frequently in digital microfluidics for manipulation and control of droplets. In this paper, the internal mechanism of EWOD is explained though establishing the geometric model of the unipolar board structure digital microfluidic chip. And the boundary conditions of equations are determined. Three coupling physical fields: electric field, flow field and temperature field in the digital microfluidic chip are simulated and analyzed. With the electric field equation coupled, Navier-Stokes equations and energy equation of the temperature control, the numerical simulation of the chip is conducted. The results show that the internal flow of micro-droplets is counterclockwise and swirling flow. The external flow velocity of micro-droplet is greater than the internal velocity. In addition, micro-droplets near the electrode applied temperature are higher than the internal temperature. Surface micromachining technologies are employed to fabricate the chip. Experimental results show that the droplet can be driven in a velocity of 25cm/s. It will possibly provide an effective solution to the manipulation of droplets.

scholarly journals Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 649 ◽  
Author(s):  
Gowtham Sathyanarayanan ◽  
Markus Haapala ◽  
Tiina Sikanen
Keyword(s):  
Mass Spectrometry ◽  
Dielectric Layer ◽  
Digital Microfluidics ◽  
Drug Distribution ◽  
Substrate Material ◽  
Ambient Mass Spectrometry ◽  
Electrowetting On Dielectric ◽  
On Chip ◽  
Ambient Ms ◽  
Digital Microfluidic

This work describes the interfacing of electrowetting-on-dielectric based digital microfluidic (DMF) sample preparation devices with ambient mass spectrometry (MS) via desorption atmospheric pressure photoionization (DAPPI). The DMF droplet manipulation technique was adopted to facilitate drug distribution and metabolism assays in droplet scale, while ambient mass spectrometry (MS) was exploited for the analysis of dried samples directly on the surface of the DMF device. Although ambient MS is well-established for bio- and forensic analyses directly on surfaces, its interfacing with DMF is scarce and requires careful optimization of the surface-sensitive processes, such as sample precipitation and the subsequent desorption/ionization. These technical challenges were addressed and resolved in this study by making use of the high mechanical, thermal, and chemical stability of SU-8. In our assay design, SU-8 served as the dielectric layer for DMF as well as the substrate material for DAPPI-MS. The feasibility of SU-8 based DMF devices for DAPPI-MS was demonstrated in the analysis of selected pharmaceuticals following on-chip liquid-liquid extraction or an enzymatic dealkylation reaction. The lower limits of detection were in the range of 1–10 pmol per droplet (0.25–1.0 µg/mL) for all pharmaceuticals tested.

Modeling and Simulation of Unequal Droplet Splitting in Electrowetting Based Digital Microfluidics

2011 ◽  
Author(s):  
Biddut Bhattacharjee ◽  
Homayoun Najjaran
Keyword(s):  
Digital Microfluidics ◽  
Vital Role ◽  
Open Loop ◽  
Loop Model ◽  
Efficient Technology ◽  
Flow Rates ◽  
Electrowetting On Dielectric ◽  
Droplet Splitting ◽  
Digital Microfluidic ◽  
Spatially Varying

Electrowetting-on-dielectric (EWOD) is a highly efficient technology to perform biological and medical analyses through the manipulation of pico- to nano-liter droplets on digital microfluidic systems (DMS). Droplet splitting is one of the basic fluidic operations that play a vital role in microscale mixing and concentration control. This paper presents the results of numerical investigation of unequal droplet splitting. In order to gain insight into the mechanism of droplet splitting, a three-electrode splitting system is simulated in FLOW-3D® for given geometry and material properties. When unequal voltages are applied to the adjacent electrodes on both sides of a droplet the distribution of electric field exerts spatially varying stress causing the deformation of the interface. The resulting unequal fluid flow rates towards the activated electrodes are determined by the coupled electro-hydrodynamics. The results of multiple simulation runs in terms of liquid flow rates with different ratios of the applied voltage will be very useful in developing the open-loop model of droplet splitting that can be later adopted to design a controller for unequal splitting in DMS.

Design of a Single-Plate Electrowetting-on-Dielectric Device

2013 ◽  
Vol 307 ◽  
pp. 14-17
Author(s):  
Tao Chen ◽  
Ming Qiang Pan ◽  
Yang Jun Wang ◽  
Ji Zhu Liu ◽  
Li Guo Chen ◽  
...  
Keyword(s):  
Driving Forces ◽  
Geometric Model ◽  
Digital Simulation ◽  
Digital Microfluidics ◽  
Simulation Software ◽  
Board Structure ◽  
Electrowetting On Dielectric ◽  
Experiment Platform ◽  
Single Plate ◽  
Digital Microfluidic

Due to its simple structure, low consumption of energy but strong driving forces, Electrowetting on Dielectric (EWOD) is used most frequently in digital microfluidics for manipulation and control of droplets. In this paper, the internal mechanism of EWOD is explained though establishing the geometric model of unipolar board structure digital microfluidic chip. The digital simulation software COMSOL Multiphysics is applied to analyze the coupling fields. The results show that external flow velocity of micro-droplet is greater than the internal velocity. Based on the theoretic analysis, surface micromachining technologies are employed to fabricate the single-plate EWOD chip. Finally, an experiment platform is set up to test this chip. Experimental results show that 2μL droplet can be driven in velocity of 10cm/s and two droplets can be merged successfully. It will possibly provide an effective solution to the manipulation of droplets.

Effects of Electrode Switching Sequence on EWOD Droplet Manipulation: A Simulation Study

2010 ◽  
Author(s):  
Hamid SadAbadi ◽  
Muthukumaran Packirisamy ◽  
A. Dolatabadi ◽  
Rolf Wuthrich
Keyword(s):  
Electrical Potential ◽  
Electrode Array ◽  
Forward Direction ◽  
Microfluidic System ◽  
Droplet Velocity ◽  
Microfluidic Chips ◽  
Switching Sequence ◽  
Electrowetting On Dielectric ◽  
Remarkable Effect ◽  
Digital Microfluidic

Electrowetting-on-dielectric (EWOD) is a new method for handling droplets on the microfluidic chips. By applying electrical potential, the interfacial energy of liquid-solid interface changes, results altering of droplet contact lines. To increase the flow rate of such a digital microfluidic system one way is to raise the droplet velocity. One important factor for enhancing droplet velocity in EWOD systems is the proper switching the electrodes or “switching sequence”. To examine the effect of switching in EWOD, the EDEW 1.0 simulation tool is used in this paper. By simulating the motion of a 1μL water droplet in a 1D electrode array, the resultant surface energy curves during the motion of droplet in different electrode switching sequences are obtained. The results show proper electrode switching has a remarkable effect on increasing of droplet velocity. To enhance the droplet velocity, the electrode, which is placed next to the droplet at forward direction, should be powered after droplet passed over it. In addition, it would be more efficient to first turn on the next electrode, and then turn off the previous one.

scholarly journals Machine vision-based driving and feedback scheme for digital microfluidics system

2021 ◽  
Vol 19 (1) ◽  
pp. 665-677
Author(s):  
Zhijie Luo ◽  
Bangrui Huang ◽  
Jiazhi Xu ◽  
Lu Wang ◽  
Zitao Huang ◽  
...  
Keyword(s):  
Machine Vision ◽  
New Technology ◽  
Digital Microfluidics ◽  
Microfluidic System ◽  
Position Information ◽  
Electrowetting On Dielectric ◽  
System A ◽  
Feedback Scheme ◽  
Voltage Signal ◽  
Digital Microfluidic

Abstract A digital microfluidic system based on electrowetting-on-dielectric is a new technology for controlling microliter-sized droplets on a plane. By applying a voltage signal to an electrode, the droplets can be controlled to move, merge, and split. Due to device design, fabrication, and runtime uncertainties, feedback control schemes are necessary to ensure the reliability and accuracy of a digital microfluidic system for practical application. The premise of feedback is to obtain accurate droplet position information. Therefore, there is a strong need to develop a digital microfluidics system integrated with driving, position, and feedback functions for different areas of study. In this article, we propose a driving and feedback scheme based on machine vision for the digital microfluidics system. A series of experiments including droplet motion, merging, status detection, and self-adaption are performed to evaluate the feasibility and the reliability of the proposed scheme. The experimental results show that the proposed scheme can accurately locate multiple droplets and improve the success rate of different applications. Furthermore, the proposed scheme provides an experimental platform for scientists who focused on the digital microfluidics system.

Magnetic Properties of Fe3O4/CoFe2O4 Composite Nanoparticles with Core/Shell Architecture

2020 ◽  
Vol 65 (10) ◽  
pp. 904
Author(s):  
V. O. Zamorskyi ◽  
Ya. M. Lytvynenko ◽  
A. M. Pogorily ◽  
A. I. Tovstolytkin ◽  
S. O. Solopan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Spinel Ferrite ◽  
Composite Nanoparticles ◽  
Core Shell ◽  
Cofe2o4 Nanoparticles ◽  
Core Diameter ◽  
The Core ◽  
Shell Particles ◽  
Interface Parameters ◽  
Shell Composite

Magnetic properties of the sets of Fe3O4(core)/CoFe2O4(shell) composite nanoparticles with a core diameter of about 6.3 nm and various shell thicknesses (0, 1.0, and 2.5 nm), as well as the mixtures of Fe3O4 and CoFe2O4 nanoparticles taken in the ratios corresponding to the core/shell material contents in the former case, have been studied. The results of magnetic research showed that the coating of magnetic nanoparticles with a shell gives rise to the appearance of two simultaneous effects: the modification of the core/shell interface parameters and the parameter change in both the nanoparticle’s core and shell themselves. As a result, the core/shell particles acquire new characteristics that are inherent neither to Fe3O4 nor to CoFe2O4. The obtained results open the way to the optimization and adaptation of the parameters of the core/shell spinel-ferrite-based nanoparticles for their application in various technological and biomedical domains.

scholarly journals Iron Based Core-Shell Structures as Versatile Materials: Magnetic Support and Solid Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 72
Author(s):  
Christian Zambrzycki ◽  
Runbang Shao ◽  
Archismita Misra ◽  
Carsten Streb ◽  
Ulrich Herr ◽  
...  
Keyword(s):  
Water Purification ◽  
Functional Materials ◽  
Core Material ◽  
Solid Catalyst ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
The Core ◽  
Shell Nanostructures ◽  
Sio2 Shell ◽  
Iron Based

Core-shell materials are promising functional materials for fundamental research and industrial application, as their properties can be adapted for specific applications. In particular, particles featuring iron or iron oxide as core material are relevant since they combine magnetic and catalytic properties. The addition of an SiO2 shell around the core particles introduces additional design aspects, such as a pore structure and surface functionalization. Herein, we describe the synthesis and application of iron-based core-shell nanoparticles for two different fields of research that is heterogeneous catalysis and water purification. The iron-based core shell materials were characterized by transmission electron microscopy, as well as N2-physisorption, X-ray diffraction, and vibrating-sample magnetometer measurements in order to correlate their properties with the performance in the target applications. Investigations of these materials in CO2 hydrogenation and water purification show their versatility and applicability in different fields of research and application, after suitable individual functionalization of the core-shell precursor. For design and application of magnetically separable particles, the SiO2 shell is surface-functionalized with an ionic liquid in order to bind water pollutants selectively. The core requires no functionalization, as it provides suitable magnetic properties in the as-made state. For catalytic application in synthesis gas reactions, the SiO2-stabilized core nanoparticles are reductively functionalized to provide the catalytically active metallic iron sites. Therefore, Fe@SiO2 core-shell nanostructures are shown to provide platform materials for various fields of application, after a specific functionalization.

scholarly journals Light-Scattering Simulations from Spherical Bimetallic Core–Shell Nanoparticles

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 359
Author(s):  
Francesco Ruffino
Keyword(s):  
Optical Properties ◽  
Light Scattering ◽  
Bimetallic Nanoparticles ◽  
Dominant Role ◽  
Scattered Light ◽  
Specific Interaction ◽  
Surface Enhanced Raman Spectroscopy ◽  
Localized Surface Plasmon ◽  
Core Shell ◽  
The Core

Bimetallic nanoparticles show novel electronic, optical, catalytic or photocatalytic properties different from those of monometallic nanoparticles and arising from the combination of the properties related to the presence of two individual metals but also from the synergy between the two metals. In this regard, bimetallic nanoparticles find applications in several technological areas ranging from energy production and storage to sensing. Often, these applications are based on optical properties of the bimetallic nanoparticles, for example, in plasmonic solar cells or in surface-enhanced Raman spectroscopy-based sensors. Hence, in these applications, the specific interaction between the bimetallic nanoparticles and the electromagnetic radiation plays the dominant role: properties as localized surface plasmon resonances and light-scattering efficiency are determined by the structure and shape of the bimetallic nanoparticles. In particular, for example, concerning core-shell bimetallic nanoparticles, the optical properties are strongly affected by the core/shell sizes ratio. On the basis of these considerations, in the present work, the Mie theory is used to analyze the light-scattering properties of bimetallic core–shell spherical nanoparticles (Au/Ag, AuPd, AuPt, CuAg, PdPt). By changing the core and shell sizes, calculations of the intensity of scattered light from these nanoparticles are reported in polar diagrams, and a comparison between the resulting scattering efficiencies is carried out so as to set a general framework useful to design light-scattering-based devices for desired applications.

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