## 3 Results and Discussion
The fluctuation of data points can be explained as the influence of local defects in the processed microchannel, Coriolis force, and Euler force in the centrifugal field (which are ignored due to the slight influence) on the droplet's motion, which eventually leads to the error of measured values (such as \(\alpha_{1}\), \(\alpha_{2}\), etc.). At this point, the SSE (the sum of squares due to error) is 0.037, which means that the error fluctuates little and can be allowed. It can be seen from Figure 6 that the actual measured velocity of the droplet has changed by 9.27% within 80 s, which is close to 11.23% of the theoretical value. The trend of the measured velocity is consistent with the theoretical velocity, and the velocity of the droplet increases slowly with the increase of the helical radius \(r\) (for every 1 mm, the velocity increases by about 0.042 mm/s, which is about 1.11% of the average velocity), which means the flow has a certain stability. The measured instantaneous velocity is slightly lower than the theoretical value, which is caused by flow errors due to the deformation. In this case, the absolute error at the minimum instantaneous velocity of the droplet is 0.34 mm/s and the absolute error at the maximum instantaneous velocity is 0.38 mm/s. The average absolute instantaneous error is about 0.37 mm/s and the error of the average velocity is about 9.81%, which is acceptable. Figure 4: The experimentally observed change in the aspect ratio of the droplet for different conditions (\(a=1.061\) mm/rad). Model predictions were also experimentally verified over a range of speeds (600-1600 rpm). Here, the maximum change value of the aspect ratio of the droplet is 0.325, and the minimum is 0.005 (Figure 7). In this case, at a low rotation speed (less than 800 rpm), the change in the droplet's maximum and minimum aspect ratio is small (less than 0.1), which indicates that the droplet's maximum and minimum aspect ratio are small (less than 0.1). Figure 5: The experimentally observed change in the transient contact angles (\(\alpha_{1}\), \(\alpha_{2}\)) and the length ratio of the contact line (\(a=1.061\) mm/rad, \(n=1000\) rpm, \(D=0.3\) mm, \(\mu_{o}=12.60\) mPa-s). Figure 6: The measured velocity and the theoretical velocity of the droplet at different locations (\(a=1.061\) rad/mm, \(n=1000\) rpm, \(D=0.3\) mm, \(\mu_{o}=12.60\) mPa-s). the deformation of the droplet in the movement process is small. At a low change rate of spiral radius of 0.673 mm/rad, the deformation degree of the droplet does not increase with the increase in the rotation speed. When the rotation speed is greater than 800 rpm, the deformation degree of the droplet increases exponentially with the change in the rotation speed. The larger the change rate of the spiral radius, the more severe the deformation degree. This is an expected result. An increase in the rotation speed and the change rate of the spiral radius corresponds to an increase in centrifugal driving force from Equation (8). Therefore, it is easier to overcome the deformation blocking effect caused by surface tension. However, at a low rotation speed, surface tension still dominates to block the deformation of the droplet, which has an influence on the prediction results of the model. At low rotation speeds (600 and 800 rpm), the average absolute error of instantaneous velocity is less than 5% of the average velocity (Figure 8). This shows better speed predictability, which corresponds to the small deformation in Figure 7. With an increase in rotation speed, the error between the prediction model and the reality increases. When the rotation speed is 1600 rpm, the average absolute error of instantaneous velocity reaches 1.34 mm/s, with the error in the same magnitude as the instantaneous velocity. At this point, the error is 16.52% of the average velocity, which shows that the error caused by deformation at a high rotation speed cannot be ignored.