Modelling
Hydraulic control assessment
Centrifugal force drive is a unique technology in microfluidic drive technology. Its system uses the centrifugal force generated by the chip in a circular motion as the driving force of the liquid flow. The flow rate of the fluid can be adjusted and controlled by changing the chip rotation speed and designing different channel configurations.
The centrifugal microfluidic technology based on the fingertip gyro drives the microfluidic chip to rotate by manual centrifugal force to construct a simulated gravitational field, that is, the centrifugal field. The flow is controlled by the volume force of the substance in the centrifugal microfluidic chip. This allows the centrifugal microfluidic chip to be designed as a closed system. The closed system means that the centrifugal microfluidic chip can realize the functions of pre-storage, release, mixing, and the reaction of reagents or samples, which significantly enhances the convenience of the chip. The characteristics of the centrifugal movement also make the centrifugal microfluidic chip usually construct flow channels and functional devices on a disc, and the arc of each part needs to be adjusted or designed according to the centre of rotation. In the centrifugal microfluidic chip, the volume force can be controlled by controlling the speed and angular acceleration. Driven by the volume force, the liquid in the flow channel will flow by itself. Since no other liquid flows in, the centrifugal microfluidic chip needs to open-air holes to let the air Enter the space where the replacement liquid was initially located to avoid generating vacuum forces to restrict the flow of the liquid. Therefore, unlike the continuous liquid flow of other microfluidic chips, the flow in centrifugal microfluidic chips is mostly a gas-liquid two-phase flow. [1] In the construction of this project, centrifugation is mainly to push the liquid flow into the next chamber. The centrifugal force required for this goal is expected to be less than the force required for filtration, so we speculate that the fingertip gyro microfluidic chip is in the driving mode The above is feasible and can be verified by modelling and actual operation methods in the future. We carried out the following experimental steps.
1.To simulate the fluid flow condition of the centrifugal chip rotated, we injected 100μL of food colouring into the chip amplification cavity, and placed a test strip in the chip test strip area in advance, and evaluated the colour flow by visual observation. The picture shows that the pigment can be injected normally and will not enter the test strip area;
Figure 1 The use of pigment injection
2.Turn the chip upside down to deposit the pigment in the amplification chamber on the other side of the chip chamber. At the same time, turn the centrifugal chip to rotate around the central axis. At the same time, the liquid in the amplification chamber enters the test strip chamber under the action of centrifugal force. The entire test strip is covered under the capillary action of the test strip. By observing the liquid flow during the rotation process and the pigment diffusion of the test strip, it is judged that the centrifugal force provided by the toggle chip can drive the liquid in the amplification chamber into the detection area of the test strip.
Figure 2 Actual driving situation
[1]Liu Xun. Research on a microfluidic chip for centrifugal particle sorting[D]. University of Chinese Academy of Sciences (Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences), 2019.
Created By Beijing Institute of Technology