[Neuroscience] Re: Curing slygard?

jonesmat via neur-sci%40net.bio.net (by jonesmat from physiology.wisc.edu)
Thu Apr 26 14:53:43 EST 2007


On Apr 12, 4:13 pm, "Bill" <connelly.b... from gmail.com> wrote:
> This may be a stupid question, but I've only ever figured out how to
> do these things by myself, is there a better way to cure slygard on
> your pipettes than holding it a foot above the bunsen burner? I don't
> want to leave it for the 48 hours that it takes for the sylgard to
> cure at room temp, (according to the dow corning website), I've bought
> into the dogma that old patch pipettes don't work that well.
>
> Blowing on it with a hair dryer makes me nervous as well.
>
> Anyone got tried and tested methods? Thanks.



Hi Bill,

I have used several approaches to curing sylgard:

1) Bunsen burner  - this actually made me laugh out loud, as I was
never able to cure the sylgard without it catching on fire!

2) Hair dryer - this is what we (i.e., my student) is using at the
moment. It works fine, but it is bulky and sloppy and I don't like it.
But it works.

3) Air dry - too slow, as you say. The pipettes might be okay the next
day if you fire polish before using them - but too slow anyway.

4) My favorite BY FAR:  You know those black upright Narashige pullers
with the big (i.e., 3-4 mm diameter) metal heating coil? Like a
Narashige P-88 or something? Well the heating coil is controlled by
the big black block falling and tripping a contact switch. It is
possible to prop the switch in the "on" position just by swinging the
little carriage out at an angle so that it just barely holds up the
block, but the block isn't pushing down on the switch itself. Okay, at
this point, you either have a P-88 in the lab, are looking at it right
now, and know exactly what I'm talking about, or you think I've
completely lost my mind. Anyway, the point is that if you turn on the
little heating coil, and keep it on in this way,  it gives a perfect
little heating element that radiates only about 1 cm at most, so you
can hold a sylgarded pipette tip next to, twirl it around slowly to
heat all sides, and voila, 5 seconds later you have a perfectly cured,
nicely formed sylgarded pipette tip.

You can also make a little metal heating coil out of nichrome wire and
a big adjustable AC power supply or something, but the Narashige is
nice, compact, and useful for pulling pipettes too! Although I like
the Brown-Flaming better for that, which is why I don't have a
Narashige in the lab, and which is why we're reduced to curing sylgard
with a hair dryer. Sad, I know.

By the way, some people "paint" the sylgard on with another piece of
glass or something, to get it within 200 microns of the tip. Forget
that. It's time consuming, fiddly, and it doesn't coat nearly as well
as this:

1) Mix sylgard in a 1.5 ml clear centrifuge tube, and mount this
upright on a piece of clay, with the cap wide open.
2) Hook up a tube to your air supply that is just big enough at the
end to squeeze snugly over the back end of your pipettes. Turn on the
air VERY GENTLY (a bubbler or something is useful to make sure it is
really very gentle).
3) Attach the tube to the back of pre-pulled pipette. If your air is
not gentle enough, then at this point the pipette will go shooting off
and stab someone in the eye.
4) Now DIP the tip of your pipette into the sylgard, to a depth of
about 0.5-1 cm. You should be able to see tiny air bubbles slowly
emerging from the tip. This ensures that the sylgard won't clog the
tip.
5) With air tube still attached and blowing (to keep the tip
unclogged), hold the pipette with sylgarded tip upwards, and hold it
next to your heating coil (or under your hair dryer) and rotate slowly
to cure.

Once you have his equipment set up, and the right airflow, it will
then only take about 10 seconds per pipette.

Cheers,

Matt









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