Progress with Closed Flow Cell
Yesterday Dean, the student from RIT, came over to help us set up our Anodic Bonder. Once we get the proper leads and connections we will be able to perform these bonding trials whenever we want without needing to travel over to RIT.
In the meantime we have continued our work with PDMS, and our attempts at creating a closed flow cell through means other then anodic bonding. As we had briefly discussed on Tuesday due to our limited bonding efficiency as of late we have begun experimenting with sealing a membrane chip to a cover slide using vacuum grease alone. We have shown that this creates a sealed system but the one issue is that even at the low flow rates generated by our micro-pump the pressure is able to cause a leak in the “weakest” portion of the vacuum grease seal.
Since Tuesday we have been playing around with super-glue and it seems to be a relatively simple and easy solution. By placing a small amount of super-glue around the top of the trough side of the membrane chips we are able to successfully seal them to a glass microscope slide. The great thing about the super-glue is that it appears that no matter how much you place on the surface of the membrane chip, when the glass slip is placed on top no super-glue travels into the membrane trough. Also, the viscosity of the super-glue is low enough so that it seals the entire chip surface leaving no gaps that can cause leaks. Using this super-glue method we have been able to seal the capillary tube entrance with vacuum grease (as we had previously been doing) and obtain flow with the micro-pump without leaks.
This afternoon Henry and I were able to make a movie showing the membrane under the dynamic flow of the peristaltic pump. It was clear that the membrane was “pulsing” with each successive beat of the micro-pump.
We were also able to introduce 15um micro beads which we observed traveling through the closed flow cell. Unfortunately before we could focus the scope properly and create a movie the membrane ruptured. The good news is that the process of creating the system is no longer dependent on our bonding efficiency and seems to be very reproducible.