15um Bead Flow through Closed Flow Cell

Based on the results obtained yesterday with the closed flow cell we reran another trial today. The closed flow system we tested today was bound using UV Ozone treatment, surprisingly this system created a relatively strong bond despite our resent results. Once the UV Ozone treatment was complete and the system had bound vacuum grease was used to ensure a full seal was made and that no leaks were formed.

The construction of this system was different than previous systems in that the PDMS was bound to the membrane side of the sample chip rather than the trough side as shown below….

A void was made in the PDMS mold whose size was just larger then the membrane itself. This allowed the PDMS to be bound to the membrane side of the sample without actually touching the membrane. This also allows the trough side of the membrane to support the system on the bottom.

Once complete this system was connected to the micro-pump and the 15um beads were flowed through which are shown below.

1) [bead flow movie here MPEG ver]

beads-flowing-in-flow-cell

2) [bead flow movie here AVI ver]

bead-flow-in-flow-cell-of-pdms-and-pnc-si

3) [relax-tension-relax movie here MEPG ver]

relax_tense_relax

PS: sorry for the small movies (small to reduce file size, ideally image compression would be better than size reduction in reducing the file size. However, somehow the image compression did not reduce the file size for mpeg converter so i reduced the image size to reduce file size instead)

The 1st  movie shows 15um beads moving through the closed flow cell. To do this we first started the flow of the 15um beads. Once the flow was established we turned off the pump and allowed some of the beads to settle onto the membrane surface so we could focus on them. The pump was then turned on again and the movie was created. The beads in clear focus are most likely moving/rolling across the membrane, and the “blurs” in the background are those freely flowing through the system.

The 2nd movie is an AVI version of the 1st movie.  It is 7X faster than the real time.  To keep the file size low i reduced the size a bit.  i cannot produce mpeg version of the movie.  It seems that somehow the software that does the conversion don’t like it when we speed up the frame rate.

The 3rd movie shows the reaction to the membrane to the pump being turned on and off. At the start of the movie the pump is off and the membrane is in a relaxed state. Shortly after the start of the movie the pump is turned on and the membrane can be observed to become more tense (no longer as “wavy” as at the start). At this point beads can also be observed to flow through the system. Near the end of the movie the pump is turned off again and the membrane returns to its original relaxed start and the beads stop flowing.

CORRECTION: it turns out that in the 3rd movie what we observed is not the membrane, but a layer of “tape”.  In order to create a rectilinear cavity in the PDMS i used either PDMS or a stack of tapes.  So i stack up layers of tapes then cut them into rectangular pieces.  However when i peel the tapes off the PDMS after PDMS is cured the 1st layer always get stuck to the PDMS.  So actually the striation that we see in the 3rd movie is not from the membrane, but from the tape.