"rangerssuck" wrote in message
...
On Sep 14, 4:22 pm, "Ed Huntress" wrote:
"Mark Rand" wrote in message

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On Mon, 14 Sep 2009 09:35:10 -0400, "Ed Huntress"

wrote:

Hey, here's something curious. I just tried this, and got funny little
drops, much smaller than I would get with an eyedropper, for example.

I took a 30-unit syringe, filled it with water, and counted the drops in
5
units. I got 11 drops -- close enough to 10 -- but they were really
teeny.
These were drops that would detach themselves and free-fall as I held
the
syringe point-down; just ordinary drops.

That's exactly 1/10 the size you're describing -- one drop from this
syringe
is 5 microliters. I see from some references online that this is the
same
size as a drop of water dispensed from a Pasteur micropipette.

So is the size of the drop that dependent on the opening from which
they're
dispensed? This was a 30-guage needle. I'd have to mike it to see the
size,
but it's *really* thin.

Might get smaller if you ground and lapped the end square. Or not...

I'll bet it would get bigger. I'll try it, but not now.



PS Are you throwing the things away after only one use? I get a couple
of
weeks out of mine.

I don't use them at all anymore. I have a pump. But I typically used them
three times. The old 28-guage ones lasted longer. 29-guage is my favorite.
With the callouses I have, the 30-guage sometimes bends right over at a 90
degree angle when I try to push it in.

I used to use them until you had to screw them in. d8-)

I have sharpened a few, when I was in a pinch, on a black hard Arkansas
stone. It works pretty well.

--
Ed Huntress



Mark Rand
RTFM

Geeze, how many people here have diabetes? Show of hands?

Mark and I are unusual in that we're both Type 1's -- juvenile diabetics.
Roughly 90% of diabetics are Type 2's. They're the adult-onset type that's
associated with age, obesity, etc. Type 1's are the ones that usually get it
in childhood and are totally insulin-dependent. The condition is an
autoimmune disease, rather than an endocrinal breakdown or overload that
leads to Type 2.

I don't but my brother does (and my mother did as well). Last time I
checked (a couple of months ago), my blood glucose was 85 an hour
after a large-ish meal so for the time being, I appear to have dodged
that bullet.

But back to the matter at hand. How about making a screw-activated
plunger pusher? You'd have some stiction problems in the syringe, but
maybe not too bad.

I don't think that much accuracy is required. Except in the
computer-controlled pumps, no one is trying to dispense fractions of a
unit -- except for babies, and the solution there is to dilute the insulin.
It's typically diluted 10:1 for babies, and it's done by professionals or by
very capable parents of those kids.

Also, Ed, are the cartridges in the pump
refillable?

No. Use once and toss. But they don't come pre-filled. You have to fill them
before using them, but the filling devices are pretty well wrecked from
one-time use.

They're usually operated by a stepper motor driving a
screw, and can deliver pretty small increments.

Right. The resolution on mine is 1/10 unit, and 100 units equal one mL (or
cc; same thing).

It should be pretty
straightforward to concoct a device with a fine-thread screw, maybe
with a 10:1 vernier dial drive for good measure.

Yeah, but it's not really needed. The insulin doses can't be matched to the
need that closely. There's some dithering around the ideal doseage because
there are so many variables involved in determining the insulin requirement
at any given time.

The old glass syringes were very slippery, but I don't know if they
make them in very narrow bores.

If it's too hard to control the movement of a syringe plunger, you
could use a diaphragm instead, which would have pretty close to zero
friction.

Just some random thoughts from a tired former designer of anesthesia
equipment.

Interesting thoughts, but they're a solution for a problem that really isn't
out there.

--
Ed Huntress