Counter Flow System Progress
Just wanted to post an update on the creation of a counter flow system using the pncSi chips from wafer 619 (the wafer with the etched trenches for the insertion of capillary tubing). Over the past few weeks Henry and I have been able to produce a few functional counter flow systems using UV Ozone bonding of pncSi to PDMS as well as supergluing of the pncSi chip to a clean microscope slide.
The diagram above shows a lengthwise cross section of the current counterflow system. The membrane side of the pncS chip is facing upwards with a piece of PDMS (with a void for fluid flow) UV Ozone bonded to it. The opposite side of the chip is the superglued to the microscope slide. Insertion of capillary tubes followed by sealing the system with vacuum grease completes fabrication.
We have successfully been able to connect the system to our micro pump and observe simultaneous flow out of the exit capillary tubes but we have not yet been able to observe flow using microbeads. Last week we created a sealed system and when we introduced microbeads we were able to observe fluid flow but no beads could be seen. When a sample of the “exit solution” was taken from each exit capillary tube no beads could be found even though we verified that we could see the beads by testing the “entrance solution”. At this time we think that the concentration of microbeads in the solution we were using was much to high and the beads might have been aggregating in the peristaltic tubing leading to the pump.
As of now it seems that we have a functional counterflow prototype system. The next step is to try to get a movie made illustrating counterflowing microbeads.
This is really tremendous progress guys. Visualization with particles would be terrific as evidence that this is really working, but quantified dialysis in a counter flow system would be publishable! Please update this post with some pictures of the real systems so everyone can see. I’ve seen them on the benches and they look pretty cool.