![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Quantitative pumping of compressed air in CD-like whole blood analysis chip Fan Jianhua 12, Deng Yongbo, Xuan Ming 1, Zhou Song 12, Wu Junfeng, Liu Yongshun 12, Wu Yihui〃 (1. Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Jilin Changchun 130033; 2.University of Chinese Academy of Sciences, Beijing 100049, China) The pumping effect of the release of the pressure of the stored gas in the compressed air chamber is reduced, and the quantitative extraction of serum on the centrifugal microfluidic chip is realized. Based on the thermodynamic equilibrium theory of isothermal gas, the relationship between the compression volume of the compressed air chamber and the liquid level position in the siphon tube and the motor speed is analyzed. The design rule of the centrifugal serum extraction structure based on the assisted action of compressed air is given. Using a polymethyl methacrylate (PMMA) as the substrate, a centrifugal serum extraction chip was fabricated by C2 laser processing, and the volume of the compressed gas at different rotational speeds and the position of the serum level in the siphon were tested. The whole centrifugal microfluidic chip consists of 5 layers, 3 layers of PMMA and 2 laminated gels. The upper PMMA of the chip includes vent holes and sample holes. The middle layer PMMA is a structural layer, including all micro channel structures. The bottom layer PMMA is packaged. In the layer, irreversible bonding is achieved with a pressure sensitive adhesive between each two layers of PMMA. The thickness of the upper layer and the encapsulation layer of the chip is 0.8 mm. The thickness of the chip structure layer is 1 mm, the thickness of the pressure sensitive adhesive is 0.25 Fan Jianhua, etc.; the quantitative pumping volume of compressed air in the CDUke whole blood analysis chip, the chip diameter is 110 mm, the chip The specific structure and size parameters are as shown.
2.2 Serum Extraction The functional unit extraction in the centrifuged microfluidic chip consists of a sample well, a vent, a sample chamber, a catheter, a separation chamber, a compressed air chamber, a siphon, and a serum extraction chamber, as shown.
The compression chamber structure is used to block the gas. The calculation model is as shown in the figure, according to the thermodynamic equilibrium theory of isothermal gas, it can be obtained: wherein: IX, respectively, the pressure and volume when the compressed air chamber is not compressed, pi, W are the air compression chamber gas when the centrifuge rotates at high speed Pressure and volume. At high speeds, the serum in the siphon and the serum in the catheter should be at the same centrifugal radius.
Therefore, the pressure pi is: among them. For the angular velocity at high speed rotation, AV-V. One% is the compressed volume of the gas, and 2 is the centrifugal radius corresponding to the compressed liquid chamber and the serum level of the separation chamber after compression. It can be known from equation (3) that the size parameter has an influence on the compression volume. There are two ways to change the compression volume: (1) when the rotation speed is constant, when the overall structure is moved toward the edge, the centrifugal radius is increased. As the centrifugal force increases, the compression volume in the compressed air chamber also increases.
(2) When the volume of the compressed air chamber is changed to increase it, the gas is easily compressed. When the rotation speed is constant, CRi + æ²) CRi - only 2) becomes smaller, and AV increases.
(a) Volume of compressed air chamber when uncompressed V. (1) Volume of compressed air chamber at a fixed speed Vi RiJR is a highly microfluidic chip calculation model for compressed air chamber and separation chamber serum level (c) The compression volume AV should be greater than V3 in order to cause siphoning. When the rotation speed is reduced, the centrifugal force is less than the pressure stored by the compressed air. The pressure stored by the compressed air begins to release, and the released pressure simultaneously starts to drive the backflow of the siphon and the serum in the catheter to the siphon. After the inner serum reaches the apex of the siphon, the compressed air continues to release and continues to release, thereby driving the serum across the apex of the siphon into the serum extraction chamber. During the gas release process, the volumetric change of the compressed gas is equal to the volume of the reflux serum in the catheter, the sum of the serum reflux volume in the siphon and the volume of the extracted serum in the serum extraction chamber. Therefore, in order to ensure the effectiveness of the serum extraction function, it should be satisfied: the angular velocity when the centrifuge rotates at a low rotational speed, V3 is Fan Jianhua, etc.; the CDUke whole blood analysis chip is shown in the quantitative pumping of compressed air in the chip (c) The sum of the volume of reflux serum in the catheter and the volume of serum reflux in the siphon.
In the process of serum extraction, the forces of blood cells in the channel are centrifugal force and Stokes viscosity, respectively; 10 are the centrifugal force field angular velocity, the volume is Vp, the radial distance of blood cells is r, p is blood cells The density, p is the density of the serum "is the viscosity coefficient, R is the blood cell radius, U is the blood cell velocity. The sedimentation rate of the hemorrhagic cells is obtained by the above two equations; it can be seen that the separation time is inversely proportional to the square of the angular velocity. .
For quantitative whole blood, the greater the rate of precipitation, the shorter the time required for separation, and the appropriate increase in rotational speed can reduce the time to separate serum.
According to the above analysis, the angular velocity is the key factor affecting the compressed volume AV, the diameter of the serum and the centrifuge radius in the siphon tube, and the larger the angular velocity, the larger the compression volume, and the larger the volume of serum extracted when the rotational speed is decreased. Therefore, it is necessary to determine the centrifuge speed based on the demand for the serum extraction volume.
The density of blood cells used was 1.103 kg/m3, the density of serum was 1.026×103 kg/m3, the average diameter of blood cells was 7.2 pm. The external standard pressure was 101 300 N/m2, and the density p was approximately 118.47 mm3. According to, =2nw/ 60, the angular velocity value at the corresponding rotational speed can be obtained, and the compressed amount at different rotational speeds can be calculated by the formula (3), and the calculated values ​​are as shown in Table 1.
Table 1 The compression volume calculated at different speeds is compressed/pL 3 The results are summarized. The larger the rotation speed, the easier the gas is to be compressed, and the more the amount of serum reflux can be driven.
The effect of the rotational speed on the compression volume In the existing centrifugal microfluidic chip research, the serum obtained by blood separation was extracted by a capillary-based siphon tube. When the chip was rotated at a high speed, the liquid level of the liquid was lower than the highest point of the siphon, and the siphon was To the action of the valve mechanism; when the rotational speed is reduced or stopped, in the case where the surface of the microchannel is sufficiently hydrophilic, the capillary force overcomes the centrifugal force and drives the liquid to flow through the highest point of the siphon until the siphon occurs. In the above process, the capillary in the siphon tube needs to be chemically or physically treated on the surface, which increases the process complexity of the chip fabrication, and the instability of the surface treatment may result in poor functional reliability and long-term stability of the chip.
The pumping action based on compressed air realizes the separation of blood at high rotation speed and the sealing and compression of gas in the compressed air chamber by connecting the compressed air chamber on the blood separation chamber, and the compressed air chamber caused by the rotation speed reduction. The pumping effect of the release of the stored gas pressure on the serum realizes the quantitative extraction of the serum on the centrifugal microfluidic chip, avoiding the surface treatment of the chip, and ensuring the long-term stability and reliability of the chip function.
When the whole blood is separated, the blood level in the separation chamber and the siphon tube are at the same centrifugal radius due to the centrifugal force. Before the blood is separated, it must be ensured that the blood cannot reach the apex of the siphon; after the blood is completely separated, the rotation speed is reduced, and the compressed gas drives the serum to flow through the apex of the siphon to achieve serum extraction. During this operation, the centrifugal radius of the apex of the siphon is the key to determining whether the siphon can effectively function as a valve mechanism. For this problem, the centrifugal radius of the liquid surface in the siphon is tested at different rotational speeds, as shown. It shows that the larger the rotation speed, the larger the centrifugal radius of the liquid surface in the siphon, and the more reliable the valve action of the siphon. The reason is that the larger the rotational speed, the larger the compression volume in the compressed air chamber.
Effect of optical precision engineering speed on the position of whole blood in the siphon tube In the whole blood separation process, in order to ensure the purity of the serum, the blood cells and the separated serum should be prevented from being mixed twice, because the speed of the centrifuge will cause the blood cells to pass through two kinds. The way back to the serum is due to the difference in concentration of blood cells and serum, and the blood cells diffuse into the serum through the interface; the second is that when the blood is rotated at high speed, the blood cells are compressed under the centrifugal force, and the deformation is generated, and the elastic potential energy is released, and the elastic potential energy is released when the rotation speed is lowered, and the blood cells are released. The separation interface with the serum is disturbed, and the blood cells are remixed with the serum. To solve this problem, the blood separation structure adopts a circular cavity to connect the microchannels, and at the same time, connects the compressed air cavity on the microchannel side, so as to sway through the blood cells and the serum level in the microchannel, and weaken the remixing, thereby ensuring the purity of the serum.
Pvc Cutting Machine,Cnc Carbon Fiber Cutting,Digital Cutting Machine,Oscillating Cutting Machine
Zhangqiu Heavy Forging Co.,Ltd , https://www.forging.nl