Startseite A numerical study on thermal bonding with preheating technique for polypropylene microfluidic device
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A numerical study on thermal bonding with preheating technique for polypropylene microfluidic device

  • Esam Abdulrahman Almezgagi EMAIL logo , Zhihong Fu EMAIL logo , Gongjian Huang und Xianyue Zhang
Veröffentlicht/Copyright: 16. Oktober 2023
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Abstract

This study presents a method for producing microfluidic chips from polypropylene using a pre-heated bonding area and thermal bonding technology. ANSYS was utilized to investigate the effects of bonding parameters and microchannel deformation and predict the bonding strength. Results show that careful control of these parameters is critical to achieve a strong and durable bond between the microfluidic chip layers. Higher bonding temperatures were found to lead to greater microchannel deformation, with deformation increasing significantly, as the temperature approached the material’s melting point. Increased bonding pressure after 1 MPa and a time of 300 s also led to greater microchannel deformation. The study’s analysis of stresses revealed that the maximum principle compressive stress on the edges of the bonding area increased significantly with pressure. Tensile testing showed that bonding strength was near failure at a tensile force of 5,500 N, indicating a bonding strength close to 1.5 MPa.

Keywords: thermal bonding; microfluidic; numerical simulation; preheated bonding area; optimizing bonding parameters

1 Introduction

In many disciplines, including chemistry, biology, environmental engineering, pharmaceuticals, and food processing, microfluidic devices are becoming more and more common (1–3). They provide several advantages over conventional macro-scale devices, such as portability, decreased reagent consumption, and faster analysis. The applications of microfluidics have expanded in many fields with the introduction of new components and techniques for fluid handling. These systems are extensively used in biological research and clinical medicine to identify and diagnose diseases, biochemical products, investigate disease symptoms, and discover drugs (4–7). To overcome the impracticality of using expensive materials like glass, quartz, or silicon, there is a requirement for cost-effective manufacturing methods utilizing polymers as the primary chip material (8). The fact that many common laboratory instruments concentrate on the microfabrication of polymer chips is another factor supporting the development toward the use of polymers as chip materials (9). The production of microfluidic systems using thermoplastics includes several techniques for duplication such as thermoforming, hot embossing, imprinting, and injection molding (10–13). In addition to selecting appropriate materials and fabricating microchannels, bonding microfluidic device is a critical factor in developing thermoplastic microfluidic systems. Even though thermoplastics share general characteristics, each material has distinct properties such as chemical composition, glass transition temperature, solvent compatibility, and mechanical rigidity (14). Microfluidic devices can be joined together using the thermal bonding technique, which involves both pressure and heat. Two thermoplastic substrates are heated to below or above their glass transition temperature (T g), which makes them rubbery and enables them to combine together under pressure. The cross-linked polymers at the interface contribute to the strong bond that results between the surfaces. The thermal bonding technique, also known as thermal fusion bonding, provides for the thermoplastic substrates bonding that are both similar and dissimilar according to the proper bonding circumstances. Microfluidic chips can be sealed using the widely accepted and trustworthy technique of thermal bonding (15). The bonding of thermoplastic microdevices depends on a number of significant factors. In order to achieve long-lasting and trustworthy bonding that prevents leaking while the device is operating, the bond strength in particular is essential. Additionally, when thermoplastic substrates are heated higher than T g during thermal fusion bonding, the elasticity modulus rapidly decreases at high temperatures, which results in the deformation of the microchannels. The best bonding conditions, including temperature, time, and pressure, must be carefully chosen in order to guarantee strong enough bond strength without influencing the microchannels in thermoplastic microfluidic devices (16). In order to get the least amount of deformation and the strongest bond, temperature, pressure, and time should be all optimized. For instance, bonding of polymethyl methacrylate (PMMA) was accomplished by using heat at 90–95°C for 10 min while applying a pressure of 1–2 MPa (17–19) According to Abgrall and Chantiwas, this technique can completely bond polymethyl methacrylate (PMMA) nanofluidic chips under particular bonding parameters (20,21). The parameters include 87°C, 0.16 MPa bonding pressure, and a time limit of 30 min (20), or a temperature of 85°C, 7 kN of force, and a time limit of 30 min (21). However, the bonding strengths achieved with this method are quite low, with Chanti reporting a strength of only 0.02 MPa. Another study applied 2.2 MPa bonding pressure for 41 min and obtained 80 kPa bonding strength (22). Also, when bonding PS–PS, 6.9 MPa bonding pressure is applied, and the result is a bonding strength of 375.5 kPa (23). To improve the bonding strength and reduce the deformation of microchannel, a numerical analysis and optimizing bonding parameters was conducted to thermally bond a microfluidic chip in this study.

This microfluidic chip, fabricated from polypropylene (PP) material and thermally bonded, will be used for biomedical applications, offering exceptional reliability in facilitating biochemical reactions. Furthermore, PP microfluidic chip impressive attributes, including high structural strength, water-tight sealing, and low nonspecific adsorption, make it an ideal choice for various microfluidic applications in biomedicine (24). The bonding area of PP material was preheated, with the cover plate temperature raised above the substrate plate temperature during the bonding process.

2 Materials and methods

2.1 PP properties and deformation model

The process in thermally bond microchannel, the temperature of the substrate and cover plates need to be controlled in the range above the glass transition temperature T g. At this time, the polymer material is in a semi-molten rubber state and exhibits viscoelastic properties. The rheological properties in this temperature range are very important for thermal bonding process. The thermal and mechanical properties of isotactic PP (25–27) are shown in Table 1 and Figures 1 and 2.

Table 1

Mechanical and thermal properties of PP

Property Value
Density 0.906 g·cm−3
Melt flow rate 80 g·10 min−1
Melting temperature 172°C
Glass temperature −6°C
Thermal conductivity 0.2
Figure 1 Temperature dependent Young’s modulus of PP.
Figure 1

Temperature dependent Young’s modulus of PP.

Figure 2 Temperature dependent coefficient of thermal expansion.
Figure 2

Temperature dependent coefficient of thermal expansion.

Through the previous studies, tensile tests of isotactic PP have been conducted under various strain rates. Additionally, relaxation tests have been carried out at different temperatures, ranging from room temperature to 120°C (25).

In this study, we have developed a viscoelastic model that takes into account the temperature dependency of the material by curve fitting a master curve at one temperature and integrating a shift function to simulate relaxation behavior at other temperatures. The temperature correction performed on the relaxation modulus is obtained, and the logarithmic transformation is performed on the time coordinate to obtain the reduced modulus–time curve relationship under three different temperature conditions 105°C, 110°C, and 120°C, as shown in Figure 3.

Figure 3 Logarithmic relation curve of constant temperature relaxation modulus at different temperatures.
Figure 3

Logarithmic relation curve of constant temperature relaxation modulus at different temperatures.

After curve fitting the obtained data, a linear fit will be applied. Subsequently, the translation theory will be employed to align the curve with the modulus curve under the reference temperature condition of 120°C. By determining the optimal translation distance, we can calculate the time–temperature equivalent factor and the time reduction factor using the W. L. F. (Williams–Landel–Ferry) equation. The time reduction factors are obtained as follows: C1 = 17.44 and C2 = 51.6.

The relaxation modulus–time curve at the reference temperature was fitted based on the prony series; the Wiechert viscoelastic parameter model of the material was used as shown in Eq. 1 (28):

(1) E ( t ) = E ∞ + ∑ i = 1 n E i exp t τ i

where E ( t ) is the relaxation modules, E ∞ represents the material’s equilibrium modulus, measured at 101.5, τ i is the relaxation time, and the relaxation modulus was obtained at 120°C and fitted to a third-order prony series in ANSYS using curve fitting property as shown in Figure 4.

Figure 4 Relaxation modulus curve and fitting curve.
Figure 4

Relaxation modulus curve and fitting curve.

The relationship between the relaxation modulus and the corresponding relaxation time parameters setting is shown in Table 2. And the expression of the relaxation modulus is:

(2) E ( t ) = 101.9 + 85.0 exp t 1.5585 + 44.4 exp t 15.9750 + 9.1 exp t 141.9195

Table 2

Relationship between relaxation modulus and relaxation time parameters

n E i τ i
1 85.0441 1.5585
2 44.4742 15.9750
3 9.1321 141.9195

2.2 Temperature and pressure optimizing model

A 3D model of two polymer chips and one heater beam with various mechanical modifications was created along with a discrete model using ANSYS Workbench software. Figure 5 shows the model, which was made up of three solid figures that represented the preheated surface bonding process. The model we used in our study includes a steel heater beam with a radiation emissivity of 0.85, located between two plates – the cover plate and the substrate plate. The heater beam is positioned closer to the cover plate to ensure that the cover plate has a higher temperature than the substrate plate. This temperature difference is important to achieve high bonding strength and to prevent excessive deformation of the microchannels in the substrate plate. The two PP polymer material chips used in the model have dimensions of 77 mm width, 70.6 mm length, 6.8 mm thickness for the substrate plate, and 0.6 mm thickness for the cover plate. The cover plate chip is placed on top of the substrate plate chip, which contains small microchannels with 1 mm length and 0.5 mm width and large microchannels with 1 mm length and 1 mm width, as shown in Figure 6. Figure 5 displays the boundary conditions for the preheating process, where the environment is assumed to have a radiation emissivity of 0.8 and convection coefficient between the chip surfaces and air is assumed to be 5 × 10−7 W·mm−2·°C−1. After setting the boundary conditions, we converted the geometric model into a discrete model by meshing the whole chip with small element size especially at microchannels into 47,742 nodes and 28,615 elements with minimum element size of 0.2 mm as shown in Figure 7, which was made up of mesh property parameterized finite elements. This allowed us to obtain accurate and precise simulation results.

Figure 5 Geometric model and boundary condition of the preheated surface bonding process.
Figure 5

Geometric model and boundary condition of the preheated surface bonding process.

Figure 6 Top view of the substrate microchannels.
Figure 6

Top view of the substrate microchannels.

Figure 7 Discrete model.
Figure 7

Discrete model.

After the preheated process is completed and the required bonding surface temperature is achieved which is 75°C, the heater beam will eject out and then start the bonding process, as shown in Figure 8. This bonding process consists of two critical stages essential for successful bonding, governed by the following boundary conditions:

  1. The environment temperature is 22°C.

  2. The temperatures of both the upper and lower chips, as well as the applied pressure during the bonding process, are considered as variables, additionally, the bonding process time is also variable. These parameters can be optimized individually, and in Section 3, specific values for each parameter will be mentioned to highlight their impact on the outcome.

  3. The convective heat transfer coefficient between the chip surfaces and air is specified as 5 × 10−7 W·mm−2·°C−1.

  4. To restrict the movement of the lower chip, a fixed support is utilized. Additionally, furthermore, considering that both chips are inside molds and the downward pressure is applied to the upper chip, the movement of the chip on all four sides is assumed to be restricted.

  5. A “frictional” contact was established at the bonding area between the two chips. In addition, the frictional coefficient of the PP material used in this context is 0.3 (29).

Figure 8 The boundary condition of the thermal-compressed bonding: (a) compress process and (b) heating process.
Figure 8

The boundary condition of the thermal-compressed bonding: (a) compress process and (b) heating process.

The first stage is the heating process as shown in Figure 8b, which is responsible for maintaining a stable preheating temperature and adjusting the bonding temperature to an optimal level. This is accomplished through the application of both above and below heat fluxes, which are labeled as 1 and 2, respectively. By carefully controlling these heat sources, the bonding temperature can be fine-tuned to ensure the highest possible bond strength and minimum deformation. The second stage of the bonding process is the compression phase, as shown in Figure 8a, which takes place simultaneously with the heating process. During this phase, pressure is applied to the bond, and the displacement of the chip on both sides is restricted, as is assumed to be inside a mold. In addition, the bonding pressure is optimized to ensure a strong, durable bond. The pressure must be carefully controlled, as too much pressure can damage the bond, while too little pressure can result in a weak bond that may not hold up under stress.

2.3 Numerical analysis of bonding strength model

Nakano et al. proposed that the strength of adhesive joints in scarves can be predicted by analyzing the distribution of interface stresses using the maximum principal stress theory (30). Similarly, Wahab et al. conducted a stress analysis to analyze the fatigue strength of adhesively bonded joints (31). Furthermore, Harris and Adams utilized the maximum principal stress approach along with finite element methods to predict the bonding strength of single lap joints (32). An increase in pressure during the bonding process positively affects the bonding strength, while also leading to a rise in compressive stress within the bonding area. As a result, a proportional relationship exists between the bonding strength and the compressive stress present in the bonding area (33). In our study, the bonding strength is determined based on the maximum principal stress theory, defining it as the maximum tensile stress that the bonded structure can withstand before failure. To quantify this, the tensile force applied during the test is divided by the bonding area, resulting in the tensile stress value, which is then converted into the corresponding bonding strength at that particular point. To apply the maximum principal stress theory, the following steps will be taken:

  1. Use the finite element analysis software (ANSYS) to simulate the thermal bonding process and obtain the stress distribution within the bonded microfluidic device.

  2. Identify the maximum principal compressive stress (σ max) in the bonded structure, which is acting on a plane that is perpendicular to the direction of the stress. Increased principal compressive stress leads to increased bonding strength.

  3. Adjust the bonding process parameters (e.g., bonding temperature, pressure) to achieve a high bonding strength.

  4. The bonding process involves specific boundary conditions, applying the optimal bonding parameters (pressure, temperature), and a bonding time of 300 s. These boundary conditions, along with any other relevant conditions mentioned in the bonding process, are applied to the 3D model to simulate the actual bonding process. During the simulation, a tensile force is applied to test the bonding strength for 100 s. At this point, the pressure is set to zero, and the entire process time is 400 s, as depicted in Figure 9.

  5. Predict the bonding strength coefficient: the bonding strength coefficient predicted based on the maximum compressive stress at the interface between the bonded surfaces. The bonding strength also obtained by calculating the force required to separate the bonded surfaces using the simulation results.

Figure 9 Boundary conditions of tensile test.
Figure 9

Boundary conditions of tensile test.

2.4 Simulation assumptions

Simulation assumptions are as follows:

  1. Steady-state conditions: assumes that the temperature distribution and thermal stresses in the bonding area have reached a steady-state condition.

  2. The convection coefficient is 5 × 10−7 W·mm−2·°C−1.

  3. Isotropic material properties: except the coefficient of thermal expansion and the modulus, the analysis assumes that the material properties, such as thermal conductivity are isotropic, meaning they are the same in all situations.

3 Results and discussion

3.1 Analysis the effect of bonding temperature in microchannels deformation

The study indicates that the dimensions of the microchannel are significantly affected by the bonding temperature. Generally, higher bonding temperatures and substrate plate temperatures lead to a greater decrease in the length and width of the microchannel. The study also shows that when applying 1 MPa pressure and 300 s bonding time, the dimensions of the small and big microchannel decrease with increasing bonding area temperature as shown in Figure 10. This is because a higher bonding area temperature increases the thermal expansion of the material. The deformation increase more after 137°C, which is near the melting temperature of the material Figure 11, illustrates the distribution of deformation in the small and big microchannels at 1 MPa, 159°C and 300 s. The red color indicates the highest deformation in the positive direction, while the blue color indicates the highest deformation in the negative direction. The corners and curves exhibit the highest deformation.

Figure 10 The effect of the bonding temperature in microchannels deformation.
Figure 10

The effect of the bonding temperature in microchannels deformation.

Figure 11 Microchannels deformation: (a) length deformation of small microchannels, (b) width deformation of small microchannels, (c) length deformation of big microchannels, and (d) width deformation of big microchannels.
Figure 11

Microchannels deformation: (a) length deformation of small microchannels, (b) width deformation of small microchannels, (c) length deformation of big microchannels, and (d) width deformation of big microchannels.

3.2 Analysis the effect of bonding pressure in microchannels deformation

Figure 12 displays the outcomes of a numerical simulation that investigated the impact of bonding pressure on the dimensions of small and large microchannels in a microfluidic chip. The study evaluated various bonding pressures ranging from 0.1 to 2 MPa at 137°C bonding temperature and 300 s bonding time and recorded the resulting reduction in the length and width of the microchannels. The results indicate that bonding pressure has a substantial influence on the dimensions of microchannels in microfluidic devices. As the bonding pressure increases, the deformation of the microchannels also increases, causing a decrease in their length and width. The relationship between bonding pressure and microchannel deformation is approximately linear, as shown in Figure 12. The deformation increases slightly until reaching 1 MPa, after which it sharply increases.

Figure 12 Effect of the bonding pressure in microchannels deformation.
Figure 12

Effect of the bonding pressure in microchannels deformation.

3.3 Analysis the effect of bonding time in microchannels deformation

Figure 13 shows the relationship between bonding time and the big microchannels deformation, when 1 MPa is applied at 137°C we can observe that as the bonding time increases, the microchannel deformation also increases. As the bonding time increases, the microchannels are exposed to higher temperatures for a longer period. This prolonged exposure to heat can cause the materials to soften and potentially deform under the applied pressure. This effect can be exacerbated if the bonding temperature is also high. The relationship between the bonding time and the deformation is linear.

Figure 13 Effect of bonding time in microchannels deformation.
Figure 13

Effect of bonding time in microchannels deformation.

3.4 Analysis the compressive stress and tensile stress in bonding area

In our research, we conducted an analysis on the influence of temperature on tensile and compressive stress during bonding. Additionally, we intend to investigate the impact of both temperature and pressure on the maximum principal stress at the bonding area. Our study will further examine the effects of two distinct temperature distributions, one with high temperature and the other with low temperature as shown in Figure 14, and assess the corresponding pressures of 1, 2, and 3 MPa for each distribution.

Figure 14 Temperatures distribution: (a) low temperatures and (b) high temperatures.
Figure 14

Temperatures distribution: (a) low temperatures and (b) high temperatures.

Figures 15 and 16 illustrate the impact of the temperatures distribution, as shown in Figure 14, on the maximum principal stress under various pressures. In Figure 15a, we observe that the maximum compressive stress along the edges of the bonding surface is approximately 1 MPa, while the maximum tensile stress within the microchannel area reaches 9.8 MPa. Additionally, the maximum compressive stress within the bonding area is 7.9 MPa.Our simulation uses negative values to indicate compressive stress, while positive values indicate tensile stress. The maximum values of the maximum tensile and compressive stresses occur at the edges of the microchannels due to the combination of factors such as thermal expansion mismatch, non-uniform bonding, geometry of the microchannels, and material properties. Proper design, material selection, and bonding process optimization can help minimize these stresses and improve the overall performance and reliability of the microfluidic chip (29). The edges of the microchannels are areas where the deformation of the material is most severe because they are located at the boundaries of the bonding area where the two layers of the chip meet. As shown in Figure 17, the stress concentrations are highest at these edges, where the material experiences the most deformation as the tensile stress in the bonding area is typically low during thermal bonding, as the substrates are not being stretched or pulled apart. However, some level of tensile stress may still be present at some places, particularly if the bonding process involves uneven cooling or if there are differences in the thermal expansion coefficients of the substrate materials being bonded (34). In Figure 15a, the maximum compressive stress on the edges of the bonding surface is roughly 1 MPa, which is approximately the same as the high temperature distribution in Figure 16a. In Figures 15b and 16b, the maximum compressive stress on the edges of the bonding surface is approximately 2 MPa. In addition, in Figures 15c and 16c, the maximum compressive stress on the edges of the bonding surface is around 4 MPa. Therefore, we conclude that the maximum principle compressive stress on the edges of the bonding area shows a minor increase with temperature but increases significantly with pressure, whereas the maximum tensile stress and compressive stress in the microchannel areas in Figures 15 and 16 increase with increasing temperature and pressure.

Figure 15 Maximum principle stress in the bonding area at low temperatures: (a) 1 MPa, (b) 2 MPa, and (c) 4 MPa.
Figure 15

Maximum principle stress in the bonding area at low temperatures: (a) 1 MPa, (b) 2 MPa, and (c) 4 MPa.

Figure 16 Maximum principle stress in the bonding area at high temperatures: (a) 1 MPa, (b) 2 MPa, and (c) 4 MPa.
Figure 16

Maximum principle stress in the bonding area at high temperatures: (a) 1 MPa, (b) 2 MPa, and (c) 4 MPa.

Figure 17 Compressive and tensile stresses in microchannels.
Figure 17

Compressive and tensile stresses in microchannels.

The maximum principle stress in the bonding area at 300 s bonding time and at low temperature distribution is as shown in Figure 15.

The maximum principle stress in the bonding area at 300 s bonding time and at high temperature distribution is as shown in Figure 16.

According to stress theory, bonding strength is influenced by the normal stress, which represents the maximum principal stress acting perpendicular to the surface. Therefore, we will optimize the bonding temperature and pressure with respect to the maximum principle stress in the edges of the bonding area. The effect of different temperatures on the compressive stress on the edges of the bonding area is shown in Table 3. Table 3 shows the compressive stress values in the bonding area of a thermally bonding microfluidic device at different bonding temperatures, substrate plate temperatures, and bonding area temperatures. The cover plate and substrate plate are the two plates that are being bonded, and the bonding area is the interface between them. Compressive stress is the force that pushes the two plates together; we can see that compressive stresses decrease as the bonding temperature and substrate plate temperature decrease. For example, when the bonding temperature is 158°C and the substrate plate temperature is 112°C, the compressive stress is 1.1 MPa. When the bonding temperature is reduced to 96°C and the substrate plate temperature is reduced to 81°C, the compressive stress decreases to 0.8 MPa. When the substrates are heated, they expand slightly, which can create compressive stress in the bonding area as they cool down and contract back to their original size. At the same time, the pressure applied during bonding can also create additional compressive stress, which can further enhance the strength of the bond.

Table 3

Effect of temperature on the compressive stress

Cover plate bonding temperature (°C) Substrate plate temperature (°C) Bonding area temperature (°C) Compressive stress in bonding area (MPa)
158 112 155 1.1
137 102 135 0.95
116 91.0 113 0.90
96.0 81.0 90.0 0.85

As we look at Figure 18, we can see that compressive stress decreases as the bonding pressure decreases. For example, when the bonding pressure is 2 MPa, the compressive stress is 9.5 MPa. When the bonding pressure is reduced to 0.1 MPa, the compressive stress decreases to 6 MPa.

Figure 18 Effect of bonding pressure on the maximum principle stress.
Figure 18

Effect of bonding pressure on the maximum principle stress.

3.5 Tensile test

After implementing the boundary conditions described in Section 2, and the bonding parameters of 1 MPa, 137°C, and 300 s, a tensile force was applied perpendicular to the cover plate to evaluate the stress in the bonding area. Figure 19a illustrates the stress outcome after a 1,000 N force was applied for 100 s. By comparing this result to the findings in Figure 16a, where the boundary conditions were applied before the tensile force was applied, it is evident that the compressive stress starts to decrease along with the bonding strength. Figure 19b demonstrates the stress results after applying a 2,000 N force for 100 s, where the compressive stress continues to decrease. Finally, Figure 19c displays the stress outcome after a 5,500 N force was applied for 100 s, where the compressive stress decreases to near zero in which the bonding fail after applying this force. After plotting the applied force and the reaction force in the bonding area as a function of time, Figure 20 illustrates that the reaction force in the bonding area is initially increasing through applying the boundary condition and decreases as the applied tensile force increases. The reaction force ultimately reaches zero when the tensile force is 5,500 N, indicating that the stress will be almost zero and the bonding strength will be close to failure at this point.

Figure 19 Effect of tensile test on the maximum principle compressive stress: (a) 1,000 N, (b) 2,000 N and (c) 5,500 N.
Figure 19

Effect of tensile test on the maximum principle compressive stress: (a) 1,000 N, (b) 2,000 N and (c) 5,500 N.

Figure 20 Tensile and reaction forces: (a) applied tensile force with respect to time and (b) reaction force in bonding area with respect to time.
Figure 20

Tensile and reaction forces: (a) applied tensile force with respect to time and (b) reaction force in bonding area with respect to time.

4 Process parameter setting

Based on the analysis discussed previously, significant deformation is observed after reaching 137°C, with an additional notable increase when applying 1 MPa pressure. By considering the compressive stress at both low and high temperatures with various pressure values, it becomes evident that the optimal combination for achieving minimal microchannel deformation and appropriate compressive stress, proportionally related to bonding strength, is at 137°C and 1 MPa pressure. With these parameters identified as the most favorable for minimizing deformation and achieving high compressive stress, a tensile test was conducted to validate and evaluate the bonding strength under these specific conditions. The results of the test indicate that the bonding is nearing failure when a tensile force of 5,500 N is applied. This force corresponds to a bonding strength of approximately 1.5 MPa at that point.

5 Conclusion

In this study, we used ANSYS Workbench software to create a 3D model of a microfluidic chip and investigate the effects of temperature, pressure, and time on the bonding process and microchannel deformation. We used the preheating of the bonding area method to insure higher temperature in the surface area than the other body of the chip in order to improve the bonding strength and reduce the deformation of microchannels, and the temperature difference between the cover plate and substrate plate are important factors in the bonding process of PP material. The preheating helps to soften the material and make it more malleable, while the temperature difference promotes better adhesion between the two surfaces. Our findings indicate that the bonding temperature, pressure, and time are critical parameters that must be carefully controlled to ensure a strong and durable bond between the microfluidic chip layers. The results show that higher bonding temperatures and substrate plate temperatures lead to a greater decrease in the length and width of the microchannel. The deformation increases more after 137°C, which is near the melting temperature of the material. Additionally, the bonding pressure has a substantial influence on the dimensions of microchannels in microfluidic devices. As the bonding pressure increases, the deformation of the microchannels also increases, causing a decrease in their length and width. The deformation increases more as the bonding pressure exceeds 1 MPa. In addition, as the bonding time increases, the microchannel deformation also increases, and the relationship between the bonding time and deformation is linear. Furthermore, our analysis of the influence of temperature on tensile and compressive stress during bonding shows that the maximum principle compressive stress on the edges of the bonding area shows a minor increase with temperature but increases significantly with pressure. These boundary conditions were applied in a tensile test to predict the bonding strength, and the results showed that the bonding is near to failure when a tensile force of 5,500 N is applied. This indicates that the bonding strength at this point is close to 1.5 MPa.

Acknowledgments

The authors thank the Central South University Electrical and Mechanical School in China.

  1. Funding information: The Fundamental Research Funds for the Central South University funded the research described in this article.

  2. Author contributions: Esam Abdulrahman Almezgagi: wrote the original draft, reviewed and edited the paper, and contributed to resources, formal aspects, and analysis; Zhihong Fu: provided supervision. Gongjian Huang: created the visualizations; Xianyue Zhang: conducted the investigations.

  3. Conflict of interest: The authors state no conflict of interest.

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Received: 2023-05-18
Revised: 2023-08-20
Accepted: 2023-08-21
Published Online: 2023-10-16

© 2023 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Artikel in diesem Heft

  1. Research Articles
  2. Chitosan nanocomposite film incorporating Nigella sativa oil, Azadirachta indica leaves’ extract, and silver nanoparticles
  3. Effect of Zr-doped CaCu3Ti3.95Zr0.05O12 ceramic on the microstructure, dielectric properties, and electric field distribution of the LDPE composites
  4. Effects of dry heating, acetylation, and acid pre-treatments on modification of potato starch with octenyl succinic anhydride (OSA)
  5. Loading conditions impact on the compression fatigue behavior of filled styrene butadiene rubber
  6. Characterization and compatibility of bio-based PA56/PET
  7. Study on the aging of three typical rubber materials under high- and low-temperature cyclic environment
  8. Numerical simulation and experimental research of electrospun polyacrylonitrile Taylor cone based on multiphysics coupling
  9. Experimental investigation of properties and aging behavior of pineapple and sisal leaf hybrid fiber-reinforced polymer composites
  10. Influence of temperature distribution on the foaming quality of foamed polypropylene composites
  11. Enzyme-catalyzed synthesis of 4-methylcatechol oligomer and preliminary evaluations as stabilizing agent in polypropylene
  12. Molecular dynamics simulation of the effect of the thermal and mechanical properties of addition liquid silicone rubber modified by carbon nanotubes with different radii
  13. Incorporation of poly(3-acrylamidopropyl trimethylammonium chloride-co-acrylic acid) branches for good sizing properties and easy desizing from sized cotton warps
  14. Effect of matrix composition on properties of polyamide 66/polyamide 6I-6T composites with high content of continuous glass fiber for optimizing surface performance
  15. Preparation and properties of epoxy-modified thermosetting phenolic fiber
  16. Thermal decomposition reaction kinetics and storage life prediction of polyacrylate pressure-sensitive adhesive
  17. Effect of different proportions of CNTs/Fe3O4 hybrid filler on the morphological, electrical and electromagnetic interference shielding properties of poly(lactic acid) nanocomposites
  18. Doping silver nanoparticles into reverse osmosis membranes for antibacterial properties
  19. Melt-blended PLA/curcumin-cross-linked polyurethane film for enhanced UV-shielding ability
  20. The affinity of bentonite and WO3 nanoparticles toward epoxy resin polymer for radiation shielding
  21. Prolonged action fertilizer encapsulated by CMC/humic acid
  22. Preparation and experimental estimation of radiation shielding properties of novel epoxy reinforced with Sb2O3 and PbO
  23. Fabrication of polylactic acid nanofibrous yarns for piezoelectric fabrics
  24. Copper phenyl phosphonate for epoxy resin and cyanate ester copolymer with improved flame retardancy and thermal properties
  25. Synergistic effect of thermal oxygen and UV aging on natural rubber
  26. Effect of zinc oxide suspension on the overall filler content of the PLA/ZnO composites and cPLA/ZnO composites
  27. The role of natural hybrid nanobentonite/nanocellulose in enhancing the water resistance properties of the biodegradable thermoplastic starch
  28. Performance optimization of geopolymer mortar blending in nano-SiO2 and PVA fiber based on set pair analysis
  29. Preparation of (La + Nb)-co-doped TiO2 and its polyvinylidene difluoride composites with high dielectric constants
  30. Effect of matrix composition on the performance of calcium carbonate filled poly(lactic acid)/poly(butylene adipate-co-terephthalate) composites
  31. Low-temperature self-healing polyurethane adhesives via dual synergetic crosslinking strategy
  32. Leucaena leucocephala oil-based poly malate-amide nanocomposite coating material for anticorrosive applications
  33. Preparation and properties of modified ammonium polyphosphate synergistic with tris(2-hydroxyethyl) isocynurate for flame-retardant LDPE
  34. Thermal response of double network hydrogels with varied composition
  35. The effect of coated calcium carbonate using stearic acid on the recovered carbon black masterbatch in low-density polyethylene composites
  36. Investigation of MXene-modified agar/polyurethane hydrogel elastomeric repair materials with tunable water absorption
  37. Damping performance analysis of carbon black/lead magnesium niobite/epoxy resin composites
  38. Molecular dynamics simulations of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) and TKX-50-based PBXs with four energetic binders
  39. Preparation and characterization of sisal fibre reinforced sodium alginate gum composites for non-structural engineering applications
  40. Study on by-products synthesis of powder coating polyester resin catalyzed by organotin
  41. Ab initio molecular dynamics of insulating paper: Mechanism of insulating paper cellobiose cracking at transient high temperature
  42. Effect of different tin neodecanoate and calcium–zinc heat stabilizers on the thermal stability of PVC
  43. High-strength polyvinyl alcohol-based hydrogel by vermiculite and lignocellulosic nanofibrils for electronic sensing
  44. Impacts of micro-size PbO on the gamma-ray shielding performance of polyepoxide resin
  45. Influence of the molecular structure of phenylamine antioxidants on anti-migration and anti-aging behavior of high-performance nitrile rubber composites
  46. Fiber-reinforced polyvinyl alcohol hydrogel via in situ fiber formation
  47. Preparation and performance of homogenous braids-reinforced poly (p-phenylene terephthamide) hollow fiber membranes
  48. Synthesis of cadmium(ii) ion-imprinted composite membrane with a pyridine functional monomer and characterization of its adsorption performance
  49. Impact of WO3 and BaO nanoparticles on the radiation shielding characteristics of polydimethylsiloxane composites
  50. Comprehensive study of the radiation shielding feature of polyester polymers impregnated with iron filings
  51. Preparation and characterization of polymeric cross-linked hydrogel patch for topical delivery of gentamicin
  52. Mechanical properties of rCB-pigment masterbatch in rLDPE: The effect of processing aids and water absorption test
  53. Pineapple fruit residue-based nanofibre composites: Preparation and characterizations
  54. Effect of natural Indocalamus leaf addition on the mechanical properties of epoxy and epoxy-carbon fiber composites
  55. Utilization of biosilica for energy-saving tire compounds: Enhancing performance and efficiency
  56. Effect of capillary arrays on the profile of multi-layer micro-capillary films
  57. A numerical study on thermal bonding with preheating technique for polypropylene microfluidic device
  58. Development of modified h-BN/UPE resin for insulation varnish applications
  59. High strength, anti-static, thermal conductive glass fiber/epoxy composites for medical devices: A strategy of modifying fibers with functionalized carbon nanotubes
  60. Effects of mechanical recycling on the properties of glass fiber–reinforced polyamide 66 composites in automotive components
  61. Bentonite/hydroxyethylcellulose as eco-dielectrics with potential utilization in energy storage
  62. Study on wall-slipping mechanism of nano-injection polymer under the constant temperature fields
  63. Synthesis of low-VOC unsaturated polyester coatings for electrical insulation
  64. Enhanced apoptotic activity of Pluronic F127 polymer-encapsulated chlorogenic acid nanoparticles through the PI3K/Akt/mTOR signaling pathway in liver cancer cells and in vivo toxicity studies in zebrafish
  65. Preparation and performance of silicone-modified 3D printing photosensitive materials
  66. A novel fabrication method of slippery lubricant-infused porous surface by thiol-ene click chemistry reaction for anti-fouling and anti-corrosion applications
  67. Development of polymeric IPN hydrogels by free radical polymerization technique for extended release of letrozole: Characterization and toxicity evaluation
  68. Tribological characterization of sponge gourd outer skin fiber-reinforced epoxy composite with Tamarindus indica seed filler addition using the Box–Behnken method
  69. Stereocomplex PLLA–PBAT copolymer and its composites with multi-walled carbon nanotubes for electrostatic dissipative application
  70. Enhancing the therapeutic efficacy of Krestin–chitosan nanocomplex for cancer medication via activation of the mitochondrial intrinsic pathway
  71. Variation in tungsten(vi) oxide particle size for enhancing the radiation shielding ability of silicone rubber composites
  72. Damage accumulation and failure mechanism of glass/epoxy composite laminates subjected to repeated low velocity impacts
  73. Gamma-ray shielding analysis using the experimental measurements for copper(ii) sulfate-doped polyepoxide resins
  74. Numerical simulation into influence of airflow channel quantities on melt-blowing airflow field in processing of polymer fiber
  75. Cellulose acetate oleate-reinforced poly(butylene adipate-co-terephthalate) composite materials
  76. Radiation shielding capability and exposure buildup factor of cerium(iv) oxide-reinforced polyester resins
  77. Recyclable polytriazole resins with high performance based on Diels-Alder dynamic covalent crosslinking
  78. Adsorption and recovery of Cr(vi) from wastewater by Chitosan–Urushiol composite nanofiber membrane
  79. Comprehensive performance evaluation based on electromagnetic shielding properties of the weft-knitted fabrics made by stainless steel/cotton blended yarn
  80. Review Articles
  81. Preparation and application of natural protein polymer-based Pickering emulsions
  82. Wood-derived high-performance cellulose structural materials
  83. Flammability properties of polymers and polymer composites combined with ionic liquids
  84. Polymer-based nanocarriers for biomedical and environmental applications
  85. A review on semi-crystalline polymer bead foams from stirring autoclave: Processing and properties
  86. Rapid Communication
  87. Preparation and characterization of magnetic microgels with linear thermosensitivity over a wide temperature range
  88. Special Issue: Biodegradable and bio-based polymers: Green approaches (Guest Editors: Kumaran Subramanian, A. Wilson Santhosh Kumar, and Venkatajothi Ramarao)
  89. Synthesis and characterization of proton-conducting membranes based on bacterial cellulose and human nail keratin
  90. Fatigue behaviour of Kevlar/carbon/basalt fibre-reinforced SiC nanofiller particulate hybrid epoxy composite
  91. Effect of citric acid on thermal, phase morphological, and mechanical properties of poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide)/thermoplastic starch blends
  92. Dose-dependent cytotoxicity against lung cancer cells via green synthesized ZnFe2O4/cellulose nanocomposites
https://doi.org/10.1515/epoly-2023-0050
Schlagwörter für diesen Artikel
thermal bonding; microfluidic; numerical simulation; preheated bonding area; optimizing bonding parameters
Creative Commons
BY 4.0

Artikel in diesem Heft

  1. Research Articles
  2. Chitosan nanocomposite film incorporating Nigella sativa oil, Azadirachta indica leaves’ extract, and silver nanoparticles
  3. Effect of Zr-doped CaCu3Ti3.95Zr0.05O12 ceramic on the microstructure, dielectric properties, and electric field distribution of the LDPE composites
  4. Effects of dry heating, acetylation, and acid pre-treatments on modification of potato starch with octenyl succinic anhydride (OSA)
  5. Loading conditions impact on the compression fatigue behavior of filled styrene butadiene rubber
  6. Characterization and compatibility of bio-based PA56/PET
  7. Study on the aging of three typical rubber materials under high- and low-temperature cyclic environment
  8. Numerical simulation and experimental research of electrospun polyacrylonitrile Taylor cone based on multiphysics coupling
  9. Experimental investigation of properties and aging behavior of pineapple and sisal leaf hybrid fiber-reinforced polymer composites
  10. Influence of temperature distribution on the foaming quality of foamed polypropylene composites
  11. Enzyme-catalyzed synthesis of 4-methylcatechol oligomer and preliminary evaluations as stabilizing agent in polypropylene
  12. Molecular dynamics simulation of the effect of the thermal and mechanical properties of addition liquid silicone rubber modified by carbon nanotubes with different radii
  13. Incorporation of poly(3-acrylamidopropyl trimethylammonium chloride-co-acrylic acid) branches for good sizing properties and easy desizing from sized cotton warps
  14. Effect of matrix composition on properties of polyamide 66/polyamide 6I-6T composites with high content of continuous glass fiber for optimizing surface performance
  15. Preparation and properties of epoxy-modified thermosetting phenolic fiber
  16. Thermal decomposition reaction kinetics and storage life prediction of polyacrylate pressure-sensitive adhesive
  17. Effect of different proportions of CNTs/Fe3O4 hybrid filler on the morphological, electrical and electromagnetic interference shielding properties of poly(lactic acid) nanocomposites
  18. Doping silver nanoparticles into reverse osmosis membranes for antibacterial properties
  19. Melt-blended PLA/curcumin-cross-linked polyurethane film for enhanced UV-shielding ability
  20. The affinity of bentonite and WO3 nanoparticles toward epoxy resin polymer for radiation shielding
  21. Prolonged action fertilizer encapsulated by CMC/humic acid
  22. Preparation and experimental estimation of radiation shielding properties of novel epoxy reinforced with Sb2O3 and PbO
  23. Fabrication of polylactic acid nanofibrous yarns for piezoelectric fabrics
  24. Copper phenyl phosphonate for epoxy resin and cyanate ester copolymer with improved flame retardancy and thermal properties
  25. Synergistic effect of thermal oxygen and UV aging on natural rubber
  26. Effect of zinc oxide suspension on the overall filler content of the PLA/ZnO composites and cPLA/ZnO composites
  27. The role of natural hybrid nanobentonite/nanocellulose in enhancing the water resistance properties of the biodegradable thermoplastic starch
  28. Performance optimization of geopolymer mortar blending in nano-SiO2 and PVA fiber based on set pair analysis
  29. Preparation of (La + Nb)-co-doped TiO2 and its polyvinylidene difluoride composites with high dielectric constants
  30. Effect of matrix composition on the performance of calcium carbonate filled poly(lactic acid)/poly(butylene adipate-co-terephthalate) composites
  31. Low-temperature self-healing polyurethane adhesives via dual synergetic crosslinking strategy
  32. Leucaena leucocephala oil-based poly malate-amide nanocomposite coating material for anticorrosive applications
  33. Preparation and properties of modified ammonium polyphosphate synergistic with tris(2-hydroxyethyl) isocynurate for flame-retardant LDPE
  34. Thermal response of double network hydrogels with varied composition
  35. The effect of coated calcium carbonate using stearic acid on the recovered carbon black masterbatch in low-density polyethylene composites
  36. Investigation of MXene-modified agar/polyurethane hydrogel elastomeric repair materials with tunable water absorption
  37. Damping performance analysis of carbon black/lead magnesium niobite/epoxy resin composites
  38. Molecular dynamics simulations of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) and TKX-50-based PBXs with four energetic binders
  39. Preparation and characterization of sisal fibre reinforced sodium alginate gum composites for non-structural engineering applications
  40. Study on by-products synthesis of powder coating polyester resin catalyzed by organotin
  41. Ab initio molecular dynamics of insulating paper: Mechanism of insulating paper cellobiose cracking at transient high temperature
  42. Effect of different tin neodecanoate and calcium–zinc heat stabilizers on the thermal stability of PVC
  43. High-strength polyvinyl alcohol-based hydrogel by vermiculite and lignocellulosic nanofibrils for electronic sensing
  44. Impacts of micro-size PbO on the gamma-ray shielding performance of polyepoxide resin
  45. Influence of the molecular structure of phenylamine antioxidants on anti-migration and anti-aging behavior of high-performance nitrile rubber composites
  46. Fiber-reinforced polyvinyl alcohol hydrogel via in situ fiber formation
  47. Preparation and performance of homogenous braids-reinforced poly (p-phenylene terephthamide) hollow fiber membranes
  48. Synthesis of cadmium(ii) ion-imprinted composite membrane with a pyridine functional monomer and characterization of its adsorption performance
  49. Impact of WO3 and BaO nanoparticles on the radiation shielding characteristics of polydimethylsiloxane composites
  50. Comprehensive study of the radiation shielding feature of polyester polymers impregnated with iron filings
  51. Preparation and characterization of polymeric cross-linked hydrogel patch for topical delivery of gentamicin
  52. Mechanical properties of rCB-pigment masterbatch in rLDPE: The effect of processing aids and water absorption test
  53. Pineapple fruit residue-based nanofibre composites: Preparation and characterizations
  54. Effect of natural Indocalamus leaf addition on the mechanical properties of epoxy and epoxy-carbon fiber composites
  55. Utilization of biosilica for energy-saving tire compounds: Enhancing performance and efficiency
  56. Effect of capillary arrays on the profile of multi-layer micro-capillary films
  57. A numerical study on thermal bonding with preheating technique for polypropylene microfluidic device
  58. Development of modified h-BN/UPE resin for insulation varnish applications
  59. High strength, anti-static, thermal conductive glass fiber/epoxy composites for medical devices: A strategy of modifying fibers with functionalized carbon nanotubes
  60. Effects of mechanical recycling on the properties of glass fiber–reinforced polyamide 66 composites in automotive components
  61. Bentonite/hydroxyethylcellulose as eco-dielectrics with potential utilization in energy storage
  62. Study on wall-slipping mechanism of nano-injection polymer under the constant temperature fields
  63. Synthesis of low-VOC unsaturated polyester coatings for electrical insulation
  64. Enhanced apoptotic activity of Pluronic F127 polymer-encapsulated chlorogenic acid nanoparticles through the PI3K/Akt/mTOR signaling pathway in liver cancer cells and in vivo toxicity studies in zebrafish
  65. Preparation and performance of silicone-modified 3D printing photosensitive materials
  66. A novel fabrication method of slippery lubricant-infused porous surface by thiol-ene click chemistry reaction for anti-fouling and anti-corrosion applications
  67. Development of polymeric IPN hydrogels by free radical polymerization technique for extended release of letrozole: Characterization and toxicity evaluation
  68. Tribological characterization of sponge gourd outer skin fiber-reinforced epoxy composite with Tamarindus indica seed filler addition using the Box–Behnken method
  69. Stereocomplex PLLA–PBAT copolymer and its composites with multi-walled carbon nanotubes for electrostatic dissipative application
  70. Enhancing the therapeutic efficacy of Krestin–chitosan nanocomplex for cancer medication via activation of the mitochondrial intrinsic pathway
  71. Variation in tungsten(vi) oxide particle size for enhancing the radiation shielding ability of silicone rubber composites
  72. Damage accumulation and failure mechanism of glass/epoxy composite laminates subjected to repeated low velocity impacts
  73. Gamma-ray shielding analysis using the experimental measurements for copper(ii) sulfate-doped polyepoxide resins
  74. Numerical simulation into influence of airflow channel quantities on melt-blowing airflow field in processing of polymer fiber
  75. Cellulose acetate oleate-reinforced poly(butylene adipate-co-terephthalate) composite materials
  76. Radiation shielding capability and exposure buildup factor of cerium(iv) oxide-reinforced polyester resins
  77. Recyclable polytriazole resins with high performance based on Diels-Alder dynamic covalent crosslinking
  78. Adsorption and recovery of Cr(vi) from wastewater by Chitosan–Urushiol composite nanofiber membrane
  79. Comprehensive performance evaluation based on electromagnetic shielding properties of the weft-knitted fabrics made by stainless steel/cotton blended yarn
  80. Review Articles
  81. Preparation and application of natural protein polymer-based Pickering emulsions
  82. Wood-derived high-performance cellulose structural materials
  83. Flammability properties of polymers and polymer composites combined with ionic liquids
  84. Polymer-based nanocarriers for biomedical and environmental applications
  85. A review on semi-crystalline polymer bead foams from stirring autoclave: Processing and properties
  86. Rapid Communication
  87. Preparation and characterization of magnetic microgels with linear thermosensitivity over a wide temperature range
  88. Special Issue: Biodegradable and bio-based polymers: Green approaches (Guest Editors: Kumaran Subramanian, A. Wilson Santhosh Kumar, and Venkatajothi Ramarao)
  89. Synthesis and characterization of proton-conducting membranes based on bacterial cellulose and human nail keratin
  90. Fatigue behaviour of Kevlar/carbon/basalt fibre-reinforced SiC nanofiller particulate hybrid epoxy composite
  91. Effect of citric acid on thermal, phase morphological, and mechanical properties of poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide)/thermoplastic starch blends
  92. Dose-dependent cytotoxicity against lung cancer cells via green synthesized ZnFe2O4/cellulose nanocomposites
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