Transporting Carrier With Droplets Driven by Electrowetting-on-Dielectric Effect

2021 ◽  
Author(s):  
Jian-Zhang (Kenny) He ◽  
Jen-Yuan (James) Chang
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Effective Distance ◽  
Control Software ◽  
Early 19Th Century ◽  
Electrowetting On Dielectric ◽  
Dielectric Effect ◽  
Droplet Movement ◽  
Hydrophobic Layer ◽  
Finger Electrode

Abstract In the early 19th century, Thomas Young (1805) and Pierre Simon Laplace (1806) published the concept of fluid surface tension, which made great contributions to the theory of surface tension. Many scholars continued to study electrowetting-on-dielectric (EWOD) technology, hoping to effectively control the movement of droplets, to make a lot of microchannels in biomedical and life applications. The purpose of dielectric and hydrophobic layer is to prevent the droplet from short circuiting when the electrode moves, and the increase of hydrophobic layer will improve the smoothness of droplet movement. EWOD technology is used in this research as the prelude of the development of soft robot. Through the combination of finger electrode and electrowetting-on-dielectric technology, a carrier is designed. The drop is driven by Arduino and LabVIEW control software, and the carrier can be moved effectively. The effective distance between the finger electrodes was found out from the experiment to change the contact angle of the drop. Drop material will use two kinds of materials, PC and mixed liquid (PC, UV), try to change the contact angle and its strength through the voltage of 0–250V, so as to find out the maximum force and suitable contact angle, hoping to support the carrier effectively. Finally, the carrier will be transported to the designated position by using drops.

scholarly journals SU-8 as Hydrophobic and Dielectric Thin Film in Electrowetting-on-Dielectric Based Microfluidics Device

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Vijay Kumar ◽  
N. N. Sharma
Keyword(s):  
Electrode Array ◽  
Spherical Shape ◽  
Dielectric Thin Film ◽  
Electrowetting On Dielectric ◽  
Design And Optimization ◽  
Microfluidic Flow ◽  
Current Design ◽  
Droplet Movement ◽  
Hydrophobic Layer ◽  
On Chip

Electrowetting-on-dielectric (EWOD) based droplet actuation in microfluidic chip is designed and fabricated. EWOD is used as on-chip micro-pumping scheme for moving fluid digitally in Lab-on-a-chip devices. For enabling this scheme, stacked deposition of thin dielectric and hydrophobic layer in that order between microchannel and electrodes is done. The present paper investigates the potential use of SU-8 as hydrophobic layer in conjunction of acting as dielectric in the device. The objective for the investigation is to lower the cost and a thin simplification in fabrication process of EWOD-based devices. We have done design and optimization of dimensions of electrode array including gap between arrays for EWOD micropump. Design and optimization are carried out in CoventorWare. The designing is followed by fabrication of device and analysis for droplet motion. The fabrication of the device includes array of electrodes over the silicon surface and embedding them in hydrophobic SU-8 layer. Water droplet movement in the order of microliter of spherical shape is demonstrated. It has been shown that an SU-8 microchannel in the current design allows microfluidic flow at tens of voltages comparable with costlier and more complicated to fabricate designs reported in the literature.

Level Set Based Modeling of Electrowetting on Dielectrics Droplet

2012 ◽  
Vol 461 ◽  
pp. 138-141
Author(s):  
Yin Xia Chang ◽  
Si Xiang Zhang ◽  
Wei Zhou ◽  
Bao Liu
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Level Set ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Navier Stokes ◽  
Electric Force ◽  
Electrowetting On Dielectric ◽  
Static Contact

This paper discusses the modeling of Electrowetting On Dielectric (EWOD) device that moves fluid droplets through surface tension effects and electric force. Instead of using a static contact angle as most papers did, we take the dynamic contact angle into count by using expression proposed by Voinov and Tanner. Firstly, the level set model and its initial values is present. Then the governing equations are discussed, and the diffused format is adopted for density and viscosity varies to smooth over the interface. The detailed expression for surface tension and electric force are also described for Navier–Stokes equations. After presenting the boundary conditions, the steps of numerical implementation are detailed.

Numerical simulation of EWOD on a printed circuit board for cleanroom-less digital fluidic manufacturing applications

2019 ◽  
Vol 38 (1) ◽  
pp. 119-137 ◽  
Author(s):  
Reza Hadjiaghaie Vafaie ◽  
Hossein Dehganpour ◽  
Abolfazl Moradpour
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Electric Field ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Angle Distribution ◽  
Content Type ◽  
Electrowetting On Dielectric ◽  
Printed Circuit ◽  
Wide Range

Purpose Digital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room facilities, while printed circuit board (PCB) technology provides high configurability and at low cost. This study aims to investigate the mechanism of electrowetting-on-a-dielectric (EWOD) on PCB by solving the multiphysics interaction between fluid droplet and electric field. The performance of system will be improved by inducing an efficient electric field inside the droplet. Design/methodology/approach To induce an electric field inside the droplet on a PCB and change the initial contact angle, the mechanism of EWOD is studied based on energy minimization method and a set of simulations are carried out by considering multiphysics interaction between the fluid droplet and external electric field. The performance of EWOD on a PCB system is investigated using different electrode structures. Findings Surface tension plays an efficient role in smaller sizes and can be used to move and control a fluid droplet on a surface by changing the interfacial surface tension. EWOD on a PCB system is studied. and it revealed that any change in electric field affects the droplet contact angle and as a result droplet deformation and movement. The electrode pattern is an important parameter which could change the electric potential distribution inside the droplet. Array of electrodes with square, zigzag interdigitated and crescent shapes are studied to enhance the EWOD force on a PCB substrate. Based on the results, the radial shape of the crescent electrodes keeps almost the same actuated contact line, applies uniform force on the droplet periphery and prevents the droplet from large deformation. A droplet velocity of 0.6 mm/s is achieved by exciting the crescent electrodes at 315 V. Furthermore, the behavior of system is characterized for process parameters such as actuation voltage, dielectric constant of insulator layer, fluidic material properties and the resultant velocity and contact angle. The study of contact angle distribution and droplet motion revealed that it is helpful to generate EWOD mechanism on a PCB which does not need more complicated fabrication processes. Originality/value The ability to handle and manipulate the droplets is very important for chemistry on-chip analysis such as immunoassay chips. Furthermore, a PCB-based electrowetting-on-dielectric device is of high interest because it does not need cleanroom facilities and avoids additional high-cost fabrication processes. In the present research, the EWOD mechanism is studied on a PCB by using different electrode patterns.

Surface Tension Actuators Droplets in Microchannels

2005 ◽  
Author(s):  
Eric Baird ◽  
Kamran Mohseni
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Unified Model ◽  
Analytic Model ◽  
Electrowetting On Dielectric ◽  
Fluid Velocities ◽  
Theoretical Results

A unified model is presented for the velocity of discrete droplets in microchannels actuated by surface tension modulation. Specific results are derived for the cases of electrowetting on dielectric (EWOD), dielectrophoresis (DEP), continuous electrowetting (CEW), and thermocapillary pumping (TCP). This treatment differs from previously published works by presenting one unified analytic model which is then simply applied to the specific cases of EWOD, CEW, DEP and TCP. In addition, the roles of equiliubrium contact angle and contact angle hysteresis are unambiguously described for each method. The model is shown to agree with experimental and theoretical results presented previously, predicting fluid velocities for a broad range of applications in digitized microfluidics.

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

Increasing Storage Modulus, Contact Angle and Surface Tension of Airway Mucus Increases Clearance by Simulated Cough Through a Model Trachea

2010 ◽  
Author(s):  
Anpalaki J. Ragavan ◽  
Cahit A. Evrensel ◽  
Peter Krumpe
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Storage Modulus ◽  
Surface Properties ◽  
Respiratory Diseases ◽  
Interactive Effects ◽  
Altered Surface ◽  
Human Trachea ◽  
Tension Increase ◽  
And Storage

Altered surface and viscoelastic material properties of mucus during respiratory diseases have a strong influence on its clearance by cilia and cough. Combined effects of the surface properties (contact angle and surface tension) and storage modulus with relatively unchanged viscosity on displacement of the simulated mucus aliquot during simulated cough through a model adult human trachea is investigated. For the mucus simulants used in this study contact angle and surface tension increase significantly as storage modulus increase while viscosity remains practically unchanged. Displacement of mucus simulant aliquots increased significantly with increasing storage modulus (and contact angle) at a given cough velocity in the range between 5 meters/second (m/s) and 30 m/s with duration 0.3 s. Results suggest that the interactive effects of elasticity and surface properties may help facilitate mucus displacement at low cough velocities.

scholarly journals Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Gang Zhou ◽  
Han Qiu ◽  
Qi Zhang ◽  
Mao Xu ◽  
Jiayuan Wang ◽  
...  
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Specific Surface ◽  
Coal Dust ◽  
Single Point ◽  
Contact Angles ◽  
Critical Surface ◽  
Volume Percentage ◽  
Surface Areas ◽  
Specific Surface Areas

Wettability is one of the key chemical properties of coal dust, which is very important to dedusting. In this paper, the theory of liquid wetting solid was presented firstly; then, taking the gas coal of Xinglongzhuang coal mine in China as an example, by determination of critical surface tension of coal piece, it can be concluded that only when the surface tension of surfactant solution is less than 45 mN/m can the coal sample be fully wetted. Due to the effect of particle dispersity, compared with the contact angle of milled coal particle, not all the contact angles of screened coal powder with different sizes have a tendency to increase. Furthermore, by the experiments of coal samples’ specific surface areas and porosities, it can be achieved that the volume of single-point total pore decreases with the gradual decreasing of coal’s porosity, while the ultramicropores’ dispersities and multipoint BET specific surface areas increase. Besides, by a series of contact angle experiments with different surfactants, it can be found that with the increasing of porosity and the decreasing of volume percentage of ultramicropore, the contact angle tends to reduce gradually and the coal dust is much easier to get wetted.

scholarly journals Effect of Pesticide Addition Sequence on the Preparation of Phytosanitary Spray Solutions

2019 ◽  
Vol 37 ◽  
Author(s):  
M.F.T. RAMOS ◽  
R.T.S. SANTOS ◽  
D.P. ALMEIDA ◽  
J.F.D. VECHIA ◽  
M.C. FERREIRA
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Propionic Acid ◽  
Biological Effect ◽  
Surface Coverage ◽  
Mineral Oil ◽  
Application Rate ◽  
Physicochemical Interactions ◽  
Effect Of Treatment ◽  
Droplet Method

ABSTRACT: The addition of adjuvants to herbicide solutions is aimed at preserving or enhancing the biological effect of treatment. However, it is commonly performed without knowledge of the physicochemical interactions between products. This study aimed to assess the effects of different addition sequences of the herbicide aminopyralid + fluroxypyr and adjuvants in the preparation of phytosanitary spray solutions on the surface tension and contact angle. Two experiments were carried out with herbicide doses of 1 and 2 L ha-1 associated with the adjuvants mineral oil (MO), silicone-polyether copolymer (SIL), and a mixture of phosphatidylcholine (lectin) and propionic acid (LEC), all at a proportion of 0.3% v v-1. The application rate was 150 L ha-1. Surface tension was measured by the pendant droplet method. Contact angle was measured on the adaxial and abaxial surfaces of leaves of the pasture weed Senna obtusifolia and parafilm. Preparation sequence did not change the contact angle on any of the analyzed surfaces at a dose of 1 L ha-1 of herbicide. For the dose of 2 L ha-1, the adjuvants SIL and LEC showed a higher spreading when previously added to the herbicide. MO resulted in a higher spreading when added after the herbicide, with higher surface coverage. Therefore, the preparation sequence influences the dispersion of phytosanitary spray solutions on targets.

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