<li>took light microscope images of the fibers obtained yesterday</li>
<li>took light microscope images of the fibers obtained yesterday</li>
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<img src="https://static.igem.org/mediawiki/2015/d/df/UCLA_14May2015_Cellulose_acetate_20pct_20x_2.jpg" alt = "cellulose acetate fiber 20% at 20x mag">
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<img src="https://static.igem.org/mediawiki/2015/d/df/UCLA_14May2015_Cellulose_acetate_20pct_20x_2.jpg" alt = "cellulose acetate fiber 20% at 20x mag" height="500" >
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<ul><li>The spun fiber is approximately the same diameter as the PEEK tubing. For reference, the inner diameter of the PEEK tubing is 127 um.</li></ul>
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<img src="https://static.igem.org/mediawiki/2015/b/b0/UCLA_14May2015_Cell_acetate_20pct_20x_2.1.jpg" alt ="cellulose acetate fiber 20% at 20x mag" height = "500">
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<ul><li>However, note that the fiber is non-uniform. This is an image of a different spot along the same fiber. This part of the fiber is likely thicker because the dope bent while coagulating in the bath.</li></ul>
Tried extrusion, this time with PEEK tubing (0.005 inch inner diameter) cut with the tubing cutter
tube length was 10 mm
dope was 20% w/v cellulose acetate with a few drops of blue food coloring
extrusion rate of 6 uL/min
fibers still don't form. Rather, the dope blobs up upon coming into contact with the water
some observations:
the syringe pump inevitably reaches a point where it stops pushing. The motor is still working, but the drive screw is clearly not moving at all (and hence, the drive block isn't moving). Curiously, dope still comes out of the tubing when the motor is stalled
periodically, an air bubble comes out from the tube -- is this an indication that there is air in the tubing? Air is something that might be providing huge back pressure against the motor's force
speaking of air bubbles, I'm not able to load a syringe with dope without there being air bubbles in the dope.
I tried removing the plunger and pipetting dope in. But when inserting the plunger back in, bubbles are formed at the plunger/dope interface.
I tried using a large diameter needle to draw dope up. But there is inevitably dead space in the needle that is introduced into the syringe as bubbles.
a thin stream can be observed rising from the tip of the tube to the surface of the water. I think that this is acetone leaving the dope. The question is, is acetone leaving the dope that's already in the coagulation bath, or leaving the dope that's inside of the tube? If it's the latter, then that may explain why the motor stops being able to push out the dope.
At the end of the day, I just removed the water bath and wiped down the tip of the tubing with acetone. I'll try again tomorrow and see what happens.
played around with the new dialysis clips. Loaded a dialysis bag with red food coloring solution to visualize leaks.
some things we learned:
apply the clips so that they clamp down on the flat part of the fold
have ample length of tubing folded over for the clips
going up to 3 folds for the tubing is ok. The fold will still be held by the clips.
started a new dialysis, using the Snakeskin dialysis tubing and dialysis clips.
we cut 15 mm of tubing for 10 mL of silk solution. This was waaaaay too big. The dialysis clips allow us to be a bit more conservative on how much tubing we use per mL solution.
start time: 5:15 pm
1st change: 6:25 pm
2nd change: 1:00 pm, May 13
3rd change: 7:00 pm, May 13
4th change: 2:00 pm, May 14
Note: no leakage observed. Good sign so far.
centrifuged the previously dialyzed silk
note to self: just use a more powerful centrifuge. It isn't worth it to split up the sample into microtubes to spin in our table top centrifuge.
ended up with 25 mL of silk
pipetted out 500 uL to dry to see our silk concentration
I am expecting a very low concentration, due to the way that our dialysis was leaking.
May 13
20% w/v dope extruded into 70% ethanol succeeded
nominal extrusion rate of 16 uL/min
I say nominal because the screw drive clearly isn’t advancing
I see now why professional fiber spinners use piston pressure instead of a drive screw syringe pump
I had to pull the coagulating mass out of the way of the dope that was continuing to advance out of the PEEK tubing
hence, at some points the fiber is thinner (but still intact)
nevertheless, even without pulling on the dope, a fiber would still form right out of the tubing
Some confounding variables:
I have no idea what pressure the pump is applying to the syringe since the drive block is not moving at all
Time may be a variable: this had been pumping for a long time before this particular experiment. Maybe all of the air bubbles from yesterday have already been purged?
Things to take care of next:
construct a robust set up where dope coming out of the tube will have adequate space so that it doesn’t hinder the dope coming out of the peek tubing
try it on silk!
construct a post-spin stretch system. This will alleviate the problem of coagulated dope interfering with dope that’s still coming out
additionally, we’ll need to have this set up anyway for silk
Once again, tried 20% w/v dope extruded into 70% ethanol, this time with the syringe pump oriented vertically
gravity pulled already forming fibers out of the way, allowing fibers to continue to form.
May 14
Degummed more silk (2.5 grams)
pipetted 100 uL of the dialyzed silk from Tuesday to determine concentration
Spun more cellulose acetate (same conditions from yesterday)
prepared LiBr solution (16 mL, 9.3M)
took light microscope images of the fibers obtained yesterday
The spun fiber is approximately the same diameter as the PEEK tubing. For reference, the inner diameter of the PEEK tubing is 127 um.
However, note that the fiber is non-uniform. This is an image of a different spot along the same fiber. This part of the fiber is likely thicker because the dope bent while coagulating in the bath.
Week 2Day 1
PCR
Ran gel
Restriction digest
Had a slice of pizza
Week 3Day 1
PCR
Ran gel
Restriction digest
Had a slice of pizza
Entries for every day of work are available through the calendars below
