Detection and analysis of coagulation effect in vein using MEMS laminar flow for the early heart stroke diagnosis

1.   Introduction

A Micro-Electro-Mechanical System (MEMS) is a miniaturized device with a combination of electronic features built on a mechanical structure. The basic functionality of MEMS is to act as a switch and also act as a transducer. In the structural view, MEMS consists of a mass suspended between two capacitive plates. This makes a difference in electric potential. MEMS sizes range from micro to millimeters [1]. The MEMS sensor model is tiny and applicable to measuring all portable consumer electronics, such as blood pressure, heartbeat, and flow measurement. Vein expansion and contract are analyzed under different degrees of freedom of design. Modeling, simulation, and verification are done using laminar flow analysis to measure the heart stroke in the early stage. A few objectives of the research article include the design of different shapes of the vein to calculate the different pressure and velocity across values. Another objective indicates the design of a vein network using vein blockages using valves to analyze the result. One more objective represents making a fifty percent open path of a vein by semi-close of vein for better analysis. The final objective designates pressure across the vein, in other words, diastole and systole are captured by a piezoelectric sensor.

2.   Design and analysis of laminar flow

2.1.   Laminar flow in vein analysis

Laminar flow analysis is the process of allowing or passing liquid or gas through the pipe without any obstacle across it. A single vein is considered to measure the pressure and velocity of blood across. Analyzing pressure with the straight vein structure is described in Figure 1. Laminar flow analysis of different shaped veins is created and analyzed. A few models designed in this article are straight pipe structures, L-type, U-type, and T shaped. The blood flow analysis is considered according to its inlet and outlet.

2.2.   Straight path design of vein

Laminar flow analysis [2] allows blood to flow smoothly across it. Position 1 and 2 of the vein are treated as inlet and outlet, respectively. The vein is modeled using COMSOL multi-physics. After the pressure analysis at the inlet, the position usually is higher than at the outlet. Simulation results in Figure 1 indicate the pressure applied at the inlet is 0.09 nw decreased to −5.48 × 10⁻³ Pascal's at the outlet. Blood velocity concentration in laminar flow is indicated in Figure 2. Under high pressure, velocity is more at the center position, there will be less across boundary walls. At inlet center position indicates the red mark at the boundary walls marked blue outlet. Figure 3 with an internal view, represents the red-blue marks. The analysis shows that the concentration is more at the center and less at the outer surface [3].

Velocity at different places is indicated in Figure 3. Velocity is more at the center than the boundaries [4]. The conclusion for a straight line/pipe is that when pressure is applied, the velocity is 0.07 m/s at the center and 0.01 m/s at the boundaries as the most negligible value.

2.2.1.   L shape design of vein

The L-type vein is created using COMSOL multiphysics, considering its inlet and outlet. Equal pressure is applied at the inlet, measuring the pressure response across the output. Fully open does not require any valves. Partially open states have been designed by applying a valve across the vein. A partial state represents the 50% open and 50% closed state, and a fully open state indicates the completely open. Figure 4 indicates the modeling of L-type vein design using COMSOL laminar flow analysis is done for the smooth representation of pressure and velocity of blood across the vein.

Fully open: when the shape is changed, the pressure gets affected. A change in pressure can be observed in Figure 4. at the bending point. Pressure at the instant is 0.05108 Pascal's, which is less than the pressure applied at the inlet. Figure 5 indicates the modeling of veins and analysis of pressure at different positions. When there were two blockages across the vein with partially open states represented in Figure 6.

There will be a blockage of the vein whenever clots are formed due to cholesterol. This phenomenon is treated as a coagulation effect. During this instant, the pressure and velocity of the blood in the vein change, and the same is modeled geometrically designed by inserting valves at various places with 50% open as indicated in Figure 7 [5]. The L-shaped vein with two blockages indicates the color change and represents the change in pressure or velocity. Red-marked pressure increases when a blockage comes in the middle of the laminar flow. A portion marked with blue color indicates increased velocity [6]. Changes that occur when the vein is 50% closed are visible in Figure 7. A portion marked with blue color indicates increased velocity [6].

2.2.2.   U shape design of vein

Figure 8 represents the fully open path without any obstacles across it and the type of vein indicates U shaped vein. Pressure and velocity can be easily measured when the flow is continuous. across the U-shaped vein, the pressure decreased near the bending and more at the outlet. Figure 9 indicates the velocity, and Figure 10 shows that the pressure analysis can be verified.

Figure 10 indicates the design of a U-shaped vein with two blockages in the path. The design is verified before the mesh and geometry analysis are finished. The pressure applied at the input is 0.09 Pascal's at the inlet. However, parameters will be affected due to the coagulation effect as velocity and pressure are inversely proportional in this case by comparing Figure 10. Moreover, in Figure 11 are compared, we know that at the blockage point, the pressure decreases and velocity increases [7].

2.2.3.   T shape/divisional flow design of vein

At the divisional point, the pressure gets reduced, so at both outlets, the pressure decreases to 0.0557 Pascal's. The speed gets reduced when velocity is more at the center of the inlet at the center and outer surface. The main reason for velocity reduction is the flow breakage due to division in the path, as shown in Figure 13. A divisional flow of blood pressure is a briefing in the T-shaped vein, where the pressure and velocity equally split into two outlets, as shown in Figure 12.

3.   Piezo-electric effect

The capacity of certain materials to “create an electric charge in response to mechanical stress” is known as the piezoelectric effect. The piezoelectric effect can also be reversible, which means materials that exhibit the direct piezoelectric effect, in other words, the creation of electricity when stress is applied, can also exhibit the opposite piezoelectric effect, which means the generation of stress when an electric field is applied. The concept of the inverse piezoelectric effect is applied, which produces acoustic waves using the inverse piezoelectric effect [8]. Red arrow marks represent the amount of pressure applied on one surface of the MEMS piezo, as shown in Figure 14.

Pressure from the vein is applied as input to MEMS piezoelectric sensor. When piezoelectric material is subjected to mechanical stress, positive and negative charge carriers accumulate in centers in material change, resulting in an external electrical field. The electrical area at the outer surface stretches or compresses when it reverses. These electrical signals detect patients suffering from secondary heart stroke conditions or abnormalities. The above analysis is based on the working of wristbands in digital stethoscopes [9]. Figure 15 indicates the functionality of the piezoelectric sensor. The design of the wristband with MEMS is represented in Figure 16. MEMS transducer, the electrical response for pressure is indicated with blue and red marks as the inlet and outlet are illustrated in Figure 17.

The data collected from the different blood pressure stages are considered to measure and analyze the blood pressure status indicated in Figure 18.

4.   Methodology

To select assumptions in COMSOL multiphysics.

• Select a 3D Model Wizard.
• In physics, select fluid flow and then select single fluid flow, then laminar flow.
• Give variable input indication as you want, then study and add.
• Geometry selection and cylinder, block, torus, or sphere per the project requirements.
• Design the model by correctly changing the axis and placing the geometric materials.
• Now select the material, blood, and liquid.
• Now determine the boundary walls by selecting from the design.
• Now select the inlet and outlet from the design and give pressure values as 0.1 or 0.09 Pascal's.
• Select the mesh and build the mesh to know any errors in the design we have done.
• If any error occurs even after designing correctly, select free tetrahedral and make it manually to make a mesh.
• Study the design by plotting, the results can be found in 2 d or 3 d.

5.   Results and analysis

The pressure of each model is evaluated using COMSOL multiphysics, as shown in Figure 19. Maximum pressure at the output node and especially in the free path compared to other paths. The coagulation effect of a vein can be easily identified when the shape of a vein is straight and has a laminar flow, as shown in Table 1.

The coagulation effect of the vein can be easily identified by blood velocity when the shape of the vein is straight and T-shaped with laminar flow detection, as described in Figure 20. The velocity of each model is evaluated using COMSOL multiphysics. There will be a maximum pressure and velocity at the outlet node and in the free path and T-shaped model compared to other types of designs, as indicated in Table 2.

6.   Conclusions

The design and analysis of different types of veins were modeled using COMSOL multiphysics. The coagulation effect on different types of veins may be analyzed by incorporating valves in the designs. A vein is considered in the free path and 50% open state. The pressure and velocity will be abnormal veins when there is a coagulation effect due to the change in pressure and velocity. These two parameters help analyze the blockages of the vein. The same values are applied to the MEMS sensor and converted into electrical signals to analyze diastole and systole values. MEMS piezoelectric model includes a gel that protects the skin from damage. The piezoelectric effect principle that has been proved using COMSOL multiphysics will help make wristband acts as a digital stethoscope different from regular stethoscopes. Pressure and velocity are the two essential parameters indicated in the blue and red marked designs. These two parameters are directly proportional in the free path laminar flow designs and inversely proportional when there is a coagulation effect. As MEMS is a tiny particle, this can be combined with a stent to protect during the second state of heart stroke.