Calibration of fluid flow velocity

To visualize the flow profile, rainbow beads (diameter:) were dissolved in the cell culture medium, which contains the dead cells. A series of pump speed(5ul/min, 15ul/min, and 45ul/min) were applied to generate a steady fluid flow. The exposure time was set to 100m so that the length of the streak(shown as a gray line in Fig. ) represents the total traveling distance of the beads during the exposure time. Fig. shows a typical image of a bead trace in the fast microfluidics channel with a pump speed of 5ul/min. To minimize hydraulic effects of the PDMS walls, the pictures were taken from the midplane of the channel providing the maximum flow velocity. Note that the traveling direction of the beads was left. Each streak was measured separately, and the average length of all streaks in one particular channel divides the exposure time was regarded as the fluid flow velocity of this channel. ^[1]

Fig. [num]: a typical method to measure the fluid flow velocity.

The data of streak length is represented in the table below:

We wrote a MatLab program to calculate the results(fluid flow velocity). Codes were shown below:

ex_fast=[630,455,610]*90;  % align the data to um/s by multiply 10 and to

ex_mid=[180,160,180]*30;

ex_slow=[48,75,80]*10;

ex_fast_mean=mean(ex_fast); ex_fast_std=std(ex_fast);

ex_mid_mean=mean(ex_mid); ex_mid_std=std(ex_mid);

ex_slow_mean=mean(ex_slow); ex_slow_std=std(ex_slow);

Note: ex_fast_mean is the mean value of fluid flow velocity of fast microfluidics channel when pump speed is 45ul/min, ex_fast_std is its standard deviation, et cetera.

The results were shown below:

柱状errorbar图 3通道 泵速45ul/min

Fig. [num] the graph of fluid flow velocity results under the pump speed of 45ul/min. It shows that the velocity rate of 3 channels is 13:100:978.

Reference

1. ↑ Maneshi MM, Sachs F, Hua SZ, A Threshold Shear Force for Calcium Influx in an Astrocyte Model of Traumatic Brain Injury.J Neurotrauma. 2015 Jul 1, 32(13) : p. 1020-9.