Gorilla Glue

micropipette Karl

Syringe and treat the water with a surfactant?

Wes

For U100 syringes used by diabetics, each unit is 10 microliters. A drop of water is 50 microliters. To dispense 1/10th of a drop of water use a 1/2 unit on a diabetic syringe.

Easier said than done. If the accuracy required is +/- half of that value -- in other words, +/- 1/20th -- you can do it with a 30-unit syringe if you have a steady hand and if you use a new syringe. Otherwise, the spacings for one unit on a 50-unit B-D "low-dose" syringe, for example, which is still a small syringe, are 1 mm each. That's extremely difficult to control.

I like the micropipette idea better, even though I've used around 38,000 syringes in my lifetime. I also could recommend an insulin pump, which is programmable in 1/10-unit doses, but they run around $6,000 +.

-- Ed Huntress

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.

-- Ed Huntress

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

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

Mark Rand RTFM

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

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

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You're probably right on the difficulty of dispensing it accurately. It was only a ballpark method with commonly available tools if you didn't want the expense of buying a micropipetter. I suppose you might be able to make your own micropipetter by attaching a dial caliper to a syringe. To get real accuracy you probably need to develop the art of dispensing small volumes or just get the right tools.

Puppy gets 1/2 ml. of Robitussin 3 times per day which is about 7 drops. I give it to her from a 50 unit insulin syringe with the needle broken off, so if I wanted a very small quantity of water, I would use the syringe with a dulled needle. Gerry :-)} London, Canada

I suspect that Puppie's current measuring device has been in use for a month or more! Gerry :-)} London, Canada

30 gauge... Gee what a wimp. Get out a REAL needle 18 large bore... First time I used one on a patient for a mainline IV push, I commented to them about the knitting needles we used because we couldn't find a brush to clean the smaller ones!

I have used a 30 on pediatrics. You don't even want to twitch with them.

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Instead of the dial caliper, set up a frame to hold the syringe, and use a micrometer thimble assembly to advance the plunger.

Or make the tools.

Enjoy, DoN.

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

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. Also, Ed, are the cartridges in the pump refillable? They're usually operated by a stepper motor driving a screw, and can deliver pretty small increments. 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.

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.

My father, who was a doctor, used to threaten to give us our vaccinations with the rusty, hooked needle. He was pretty warped at times.

As a nurse in a somewhat isolated area, my mother kept a sharpening stone readily at hand. Gerry :-)} London, Canada

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 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.

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.

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

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.

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

-- Ed Huntress

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Well ... I have a mild form at present -- controlled by pills instead of injections.

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A diaphragm has the problem of giving variable delivery for a given motion, depending on whether it is positively curved, nearly flat, or negatively curved at the moment.

Enjoy, DoN.

All can be compensated for - what we used to call SMOP (simple matter of programming).

564

Yeah but... When you're upt to your neck in alligators, it's hard to remember that you came here to drain the swamp.

We weren't talking about dispensing infinitesimal doses of insulin (and wouldn't it be cool if there was continuous monitoring and feedback that could take advantage of that precision?). The problem at hand is dispensing infinitesimal doses of water, for the purpose of mixing foaming Gorilla Glue. From Doug's original post (at the top of this thread):

So, in that context, would it be possible to refill an insulin cartridge and construct a simple dispenser to hold it and apply screw pressure to the plunger?

RS