10 June 2008

Objectives

We have written an experimental procedure of the PIV system earlier in the week. As Hariz missed the first part of the training, we decided to run the experiment again with our own experimental procedures and Hariz doing it from the start. Also, we wanted to see how the differential pressure between the two inlets will affect the liquid flow in the liquid.

What was done

As we were the pilot research group for this experiment, we were asked to write down a list on procedures by our supervisor Mr. Ting. This is to act as a reference for the future FYP groups that will be doing this experiment and also enable us to do the experiment without any doubts. So as to ensure that the experimental procedures are user-friendly, Hariz was tasked to run the whole experiment by just referring to the experimental procedures.

Our experimental procedures are still subjected to changes. After more feedback from our project supervisor, we will amend it.

For the differential pressure, we decided to try out how the difference in height of the 2 inlet syringes affects the way the fluid flow. By having a difference in the height between the syringes, it creates a differential pressure. Initially we thought that the speed of the higher placed syringe would travel much faster then the lower placed syringe. But after seeing the results from the software, we found out that the liquid flow in the channel within the chip was turbulent as the vectors calculated by the software were all over the place. It also shows some mixing.

We also noticed a particular pattern from the few runs that we conducted is that there is a vacuum effect at the junction where the 2 streams meets, this vacuum effect causes some of the liquid to flow to the lower positioned inlet syringe.

Another pattern we found out is, there is some circular patterns from the vectors after the junction. We conclude that there is mixing occurring at these circular patterns and it continues mixing due to the incoming stream of fluid.

Problems

We are unable to testify fully that the circular patterns plotted out by the software pattern are mixing as we made a mistake by starting with a high differential height between the 2 syringes.
For the vacuum created, we are only able to conduct a firm conclusion when we have tested with various differential heights.

Solution

To solve the above problems, we are going to start of with a minimal differential height to the differential height we did this week. By doing this, we are able to see the pattern on each stage conducted, thus, concluding into a firm statement.

Conclusion

This week’s experiment on the differential height will give us a firm foundation on the topic mixing for micro fluidics. Though the lesson we learnt today is based on gravity creating a differential pressure, we are able to learn the basic foundation of how fluid flows in such condition. By having this foundation knowledge, we are able to proceed into a more challenging task for pressure driven by using 2 syringe pumps, both at different speeds.
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