COMSOL Multiphysics - Research Proposal Example

COMSOL Multiphysics Abstract : A simulation of an electric field is performed using COMSOL Multiphysics in order to calculate the electric potential and electric field strength distribution between the electrode arrays, as well as to calculate the electric potential and electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes. In this report, we present the results made possible by the use of the electrostatic module of COMSOL Multiphysics. This module deals with the movement of an electric field and the electric potential between the electrodes. Not only this, but the models also lead to find the strong and weak points of electric potential and the electric field between the electrodes. Also illustrated is how the electric field and electric potential distributes between the electrodes. Introduction: The electric field has long since become one of the most important things in our lives, regardless of whether or not it is even noticeable. The use of electric fields in any industry are numerous, especially in microtechnology; there are even fields that do not realize the importance of electric fields. A prime example would be within biology cells, where the electric field is used to move the cell, or separate or analyze the cell. An electric field is the impact of other electric charges, which can also be produced from other charges within the same vicinity as the key charge. Michael Faraday stated that the result of electric fields within the body that are fully charged will show in the space around it, going from a strong charge (positive charge) to any of other charges within the area (negative charge) as shown in figure (1). Figure (1): the electric field between positive and negative charges. The electric field operates between the two charges in the same way that gravitational fields work between two masses; accordingly, it can be written in the following equation: E = Where E is the intensity of the electric field, F is the force with which the electric field applies it, with Q being the charge. However, according to Coulomb’s Law, the electric field can given as such: In regard to the permittivity of free space (electric constant), q is the charge and r is the distance. On the other hand, Gauss’s law states that the electric flux through any close surface is proportional to the enclosed electric charge. Q = Where Q is the electric flux, E is the intensity of the electric field and S is the area of surface. The ability of the electric field on the work called electric potential is usually measured in units of voltage. The lines of electric potential are called equipotential lines. If the electric potential lines become closer it means that the stronger the force is on the object, but if it is far from each other it means the strength of the force becomes weaker on the object. Figure 2 shows the electric field lines with electric potential lines for two different cases . Figure 2 : illustration for electric field lines with electric potential lines. Electric potential between two parallel plates can be given as follows: dV = - E dL We can find the relationship between the electric field and the electric potential from the previous equation: E = - dv/dl E = - V/d However, in this report we have a typical electrode geometry used to extract biological cells from a sample using the AC electrokinetic process known as dielectrophoresis. The diagram(figure 3) shows three microelectrodes, illustrated in green, red and blue, which are energised with +1V, 0V and -1V electrical voltages respectively. The inter-electrode region (white) is filled with an oil which exhibits a relative permittivity of 200. Figure ( 3) In this paper we will use COMSOL Multiphysics to calculate the electric field and the electric potential in two different cases. COMSOL Multiphysics is the programme of software with a range of different programs for physics and engineering applications for analyzing the elements, solver and simulation. COMSOL Multiphysics is used due to the the need for faster and easier analysis with a lower cost. It has also led to a good understanding of the problems. In the first case, we will calculate the electric potential and electric field strength distribution between the electrode arrays. However, in the second case, we will calculate the electric potential and electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes. Not only this, we will also present the results for the models of two cases which, mentioned above, using COMSOL Multiphysics. These models deal with the movement of the electric field and electric potential between the electrodes; the density of the electric field between the electrodes; and defining the areas where the electric potential is strong and where is it weak. Also, the shapes which the electric potential will take when it applies the force between the electrodes can also be observed. Methodology (modelling) : (A) ( B) Figure 4: representation of the two geometries that were simulated, A : from 2D and the result after the solve will in 2D. B: from 2D but the result after the solve will be in 3D. We deal with two geometries shown in figure 4 (A,B). We need, as mentioned before, to calculate the electric field and the electric potential for figure 3, which is a typical electrode geometry used to extract biological cells from a sample using the AC electrokinetic process known as dielectrophoresis. There are three microelectrodes, illustrated in green, red and blue, which are energised with +1V, 0V and -1V electrical voltages respectively. The inter-electrode region (white) is filled with an oil which exhibits a relative permittivity of 200. First of all, we used COMSOL Multiphysics to create diagram A in figure 4 to calculate the electric potential and the electric field strength distribution between the electrode arrays. In model A it was dealt with electrostatic in 2D, which was Engineered apart from the three microelectrodes between +1V and 0V. By clicking on the boundary settings we choose to put the top electrode +1V and by the same way we put the bottom electrode 0V. After that, going to subdomain settings from the physics button, the equation which was dealt with in this case is: Where the relative permittivity equals 200, the space charge density which equals 0 c/m3 and d is the thickness for the electrodes which equals 1 m. Finally, we pressed solve to get the result. However, in order to calculate the electric potential and the electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes. We deal with model B (figure 4) in 3D of electrostatic, designing a top electrode with 1V; after that the bottom electrode with 0 V, finally joining them by a square with a symmetry volt (v=0) from boundary settings where V =V0. After that, by going to the subdomain setting to see the equation which deals with this model: Where c/m3 is the space charge density, water permittivity which equals 1. Furthermore, we put the thickness for the electrodes 5μm, also the distance above electrodes which will be extended to 20 μm and it will be considered that the water distributed in 100 μm above and below the electrodes. At the end, the solve button will be pressed to get the result. Results and discussion: The results for the first model A (figure 4) from the simulation of the electric field between the electrodes can be calculated by the electric potential and the electric field strength distribution between the electrode arrays as it was as shown below in figure 5. The strength of the electric potential point between 0.9 V and 1 V, the weakness of the electric potential point between 0 and 0.1 and between 0.6 and 0.8, where we can see that the electric field had fluctuated between 0.4 and 0.2. However, the fixed point where the electric potential was constant was 0.5. It is clear from diagram A1 that the electric potential strength focused on the electrode which has a high volt (1 V) and is distributed slowly to the electrode which has a low volt (0V). A1 A2 Figure 5: this shows the result for the simulation of the electric field from model A in figure 4; the diagram A1 illustrates the electric potential distribution between the electrodes but A2 represents the electric potential lines. The electric potential lines can be seen from diagram A2. If the lines are close to each other it means that the electric potential becomes stronger, but if it farther from each other it means that the electric potential is wake in these areas. Also, we can see that the corners of the electrode(1v) have the strong electronic potential points because the electric potential lines become very close. By using mesh the result will be clear, as can be seen in A2; also we can see that the areas which are far from the corners have electric potential with less strength than the corners. These are the results for the electric potential. Now we will present the results for the electric field. A3 Figure 5: shows the results for the simulation of electric field from model A. In figure 4 the diagram A3 illustrates the electric field distribution between the electrodes but A4 represents the strong and weak areas for the electric field. The result in diagram A3 illustrates the direction and distribution for the electric field between the electrodes. The electric field moves from the electrode +1v to the electrode 0v in the lines. We also noted that the electric field was nonuniform, which means that the electric field distribution is in a different direction. This confirms the theory that states that the electric field moves from high charges to low charges in lines. On the other hand, diagram A4 represents the areas where the electric field was high, where it was weak and where it was concentrated. It can be seen that the electric field was concentrated on the top of electrodes, especially in the corners. By using mesh we can get the high accuracy for the electric field. The high point for the electric field where it is strong was between 7and 7.329 (red areas), the low point where it is weak was between 0 and 1 (blue areas), and the fixed point for the electric field was 4, but between 2 and 3 it was fluctuated, as well as between 5 and 6. It can be noted that the electric field is strong in the corners and weak when we moved away from the corners. Figure 6 confirmed this. We took apart the digram A3 to show an accurate picture for the electric field in the corners and, before that, we used the mesh. The high point for electric in this case was between 16 and 17 and the wake point was between 0 and 2 . However , the fixed point was 10 where the electric field was constant and between 12 and 16 it was fluctuated, yet also the same between 8 and 4. Figure 6: shows the strong areas for the electric field (part from A3) before using mesh Now we will look for the results from the model B in figure 7 where we needed to calculate the electric potential and the electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes. B1 B2 Figure 7: shows the result for the simulation of the electric field from model B in figure 4. The diagram B1 illustrates the electric potential distribution between the electrodes but B2 represents the electric potential lines. The results for the first model B (figure 4) from the simulation of the electric field between the electrodes to calculate the electric potential and electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes as it was shown above in figure 7. The strong electric potential point between 0.9 and 0.974 where the weak point for the electric potential was between 0 and 1. The fixed point for the electric potential was 0.5, where the electric potential was constant but between 0.6 and 0.8 it was fluctuated, as well as between 0.4 and 0.2. It can be noted that the electric field distribution started from the electrode (+V) where the voltage was high. Going to the electrode which has the low voltage (0V), in diagram B4, we can see that the electric potential lines explain where there was strength (red areas), where there was weakness (blue areas) for the electric potential, and where it was constant (green area) and how it fluctuated (orange and light blue areas). Now we will present the results for the electric field, which is shown below in figure 8. B3 B4 Figure 5: shows the results for the simulation of the electric field from model B in figure 4. Diagram B4 illustrates the electric field distribution between the electrodes but B3 represents the strong and weak areas for the electric field. We can see from diagram B3 that the electric field concentrated on the top of the electrodes (+1V and 0V) and in this area we can also see the strong points for the electric field (red area), which was between o.9 *10-6 and 1*10-6 and the weak area (blue area) which was between 0 *10-6 and 0.4*10-6. However, the fixed point for electric field in this case was 0.6 *10-6. The fluctuated point in this case was between 0.7*10-6 and 0.9*10-6 , as well as between 0.5*10-6 and 0.3*10-6. On the other hand, diagram B4 illustrates the distribution for the electric field between the electrodes. It shows that the electric field is nonuniform as it has moved in different directions from the electrodes which had a high voltage ( +1V) to the electrode which had a low voltage (0V). It is clear from the two models and their results, which produced using COMSOL Multiphysics for the simulation of the electric field between the electrodes that the electric field and electric potential move between the electrodes according to the physics equation and theories which were mentioned previously in the introduction. Conclusion: The current paper aimed to simulate the electric field between the electrodes which shows a typical electrode geometry used to extract biological cells from a sample using the AC electrokinetic process known as dielectrophoresis. It is because of that the electrodes are symmetric that we decided to take apart from it and model it (+1Vand 0 V) from the centre of the electrodes using COMSOL Multiphysics. We made two geometries to calculate the electric field in two cases. First, to calculate the electric potential and electric field strength distribution between the electrode arrays. Second, to calculate the electric potential and electric field distribution 20μm above the electrodes arrays if the electrodes are 5μm thick and the water extends 100μm above and below the electrodes. It was found that the electric field concentrated on the top of electrodes, especially in the corners which have strong electric field points. This is due to the fact that the electric field was nonuniform and it was moved from the electrode, which had high voltage, to the electrode, which had low voltage. We also noted that the lines of electric potential were very close in the corners, which led to a strong electric potential in that area. However, we note that the strong point for the electric field and electric potential were near to the electrode, which has high voltage, and the weak point for the electric field and electric potential were near the electrode, which has a low voltage. Read More