Random Thread #1

[flying fish]

I am looking for an efficient solvent (or whatever) for removing polystyrene microspheres and other organic debris from (glass) microfluidic channels...I googled polystyrene solvents and got this: http://www.bangslabs.com/support/pdf/Solvent_Listing.pdf which lists a bunch of organic solvents. Out of those, the only one I tried was Acetone, which dissolved it painfully slowly.

 

Maybe it's worth trying different solvents, like Xylene, but would something like Piranha solution attack them more rapidly? Would piranha release O2 rapidly and pressurize the channel? Based on the 100 micron square cross section of the channel, and the perfect sealing if the chip were thermally bonded, I can see it being pressurized to hundreds of PSI and surviving. Plus, with such low volumes, it seems unlikely that O2 could be rapidly released anyway. But on the other hand, the path length to the end of the channel could be quite long, and of course I wouldn't want to risk breaking the chip.

 

And then there's the whole issue that the only lab we have that is designed for handling acids is the HF lab, and they probably don't want me working in there (nor do I really want to be working in there).

[tentacles]

I would suggest trying a more aggressive solvent, like MEK or methylene chloride, perhaps THF if you can get it. Here's one you could try cheaply and easily - go to the hardware store and try to find *CLEAR* PVC primer, not the purple dyed stuff. It's a solvent cocktail that dissolves even PVC with quite some ease. I found the clear stuff at a local industrial/professional plumbing/electrical place.

[Bonny]

I am looking for an efficient solvent (or whatever) for removing polystyrene microspheres and other organic debris from (glass) microfluidic channels.

 

IIRC correctly, citric acid will dissolve polystyrene quite nicely, not sure about the other organics though.

[FrKoNaLeaSh1010]

tentacles as far as I know pvc primer is a mix of acetone and MEK with some dyes added in.

[asilentbob]

THF:

http://householdproducts.nlm.nih.gov/cgi-b...as=TblChemicals

 

DCM:

http://householdproducts.nlm.nih.gov/cgi-b...amp;prodcat=all

[tentacles]

tentacles as far as I know pvc primer is a mix of acetone and MEK with some dyes added in.

 

No PVC primer I've ever seen is just those two, I will grant you those are the primary ingredients, but it's the THF that really does the grunt work of the stuff, that causes PVC to *immediately* dissolve. Ever tried to dissolve PVC in straight acetone or MEK? Takes forever, and never completely dissolves.. You can entirely dissolve PVC in a solution with some THF.. Polystyrene has no chance at all...

 

Check out silentbob's link to the THF info page - I think every product on that list is either PVC cement, or PVC primer.. or CPVC cement/primer.

 

I might try using PVC primer as solvent for a PVC heavy star comp some time, see if I can't use the PVC as the binder.

Edited December 11, 2008 by tentacles

[flying fish]

Thanks for the solvent advise (to all that responded). Looks like I've got at least a couple options to try. I also wonder how quickly large blockages could dissolve in a small cross-section microfluidic channel (100x100 microns). I want to investigate the solvents because if it dissolves it fast enough (say, such that a 1 inch length of channel jammed packed with Polystyrene spheres could be completely removed in a matter of hours or less, attacking it from only one side), then it would be worth using a permanently bonded microfluidic chip for the work that I am doing.

 

I'm also occasionally getting little fiber thingys that jam up in the channel...I don't know if they just come out of the air or what? But perhaps that's where exotic acidic cleaning solutions (like piranha or HF) could come in handy if the Polystyrene solvents don't also attack the fibers.

 

Right now I'm using a chip that i have to mechanically clamp a cover plate onto, and it can be a real pain in the ass to get a good leak-proof seal. But the plus side is that cleaning it out is just a matter of popping off the cover plate and rinsing out the exposed channel and hitting it with canned air. If I had a way of cleaning bonded chips that was even halfway as effective, it would probably be worth using a bonded chip.

Edited December 11, 2008 by flying fish

[xxxjanusxxx]

I saw an improvised cometpump a while back in this topic and I want to show you ours. I think that it's better to press something to a comet then to use that improviced pump. Well here's ours.

The Id of the comet is 40mm and the length about 60 or 70 mm I guess. The weight is somewhere between 100-120 grams. This is actually TT with +10% added Al and +10% added Ti. It looks nice when it burns, but we still have to find a good mortar for these.

[mormanman]

Has anyone heard of induction heating? That stuff is cool. I want to either make one or buy one but it would be hella expensive. Swede, you know how to make one right. You can build a radial nine I'm sure you could figure out a way to build one of these. Build one of these and you can cast your own blocks.

[Swede]

Find me some plans! I'll build it... but it'll be small! The experimental mini's I've seen are nothing more than a couple turns of Cu pipe, maybe 1/4" OD tubing, formed into a spiral with an ID of 3 inches or so. I believe they were used for heating ball bearing races or similar. A big-assed transformer is needed too, or there'll be minimal power output.

 

Induction furnaces for a home shop are usually about $10,000, and that'll buy a lot of propane, so that's why you don't see too many of them.

 

Check out "Rio Grande" jeweler's catalogue https://www.riogrande.com/home/... they have some induction minis for precious metals. I agree, they are way cool.

[asilentbob]

You might look into microwave use, though you probably have before. I would do it if I could find the right stuff...

[crazyboy25]

If your serious about induction heating which I doubt you are ask around on sciencemadness a member there 12AX7 is into this kind of stuff.

[rev.redneck]

I made a small I.H. once using microwave capacitors, it would quickly melt a beer can, its pretty simple realy just rapidly creating and collapsing a magnetic field causing an eddy current.

[Richtee]

Find me some plans! I'll build it... but it'll be small! The experimental mini's I've seen are nothing more than a couple turns of Cu pipe, maybe 1/4" OD tubing, formed into a spiral with an ID of 3 inches or so. I believe they were used for heating ball bearing races or similar. A big-assed transformer is needed too, or there'll be minimal power output.

 

Hmm now I may be wrong, but ain't an induction furnace basically a transformer primary inducing current into a pretty direct shorted secondary...EG..the "meltee"?

Edited December 15, 2008 by Richtee

[Swede]

It sounds like what you need for a baby induction device is as big a transformer as you can find, switch the primary with a heavy-duty solid state relay, thus requiring a simple 5VDC signal to turn "on" the device. Attached to the SS relay is your control electronics. A microprocessor like a PIC16F876, an external potentiometer which is sampled by the code in the PIC, thus controlling the frequency and rate of collapse. The 5VDC PIC chip itself could drive the SS relay, as most good relays don't draw more than 10mA or so on the control side, with <1V being OFF and >3V being ON.

 

The secondary is a 3/8" soft copper tubing wrapped into a coil. The control electronics could be tested first on a REALLY small system, say a 500VA transformer and #8 solid copper secondary. Attach a thermocouple or RTD to a test sample, and begin some careful testing, note taking, and reprogramming of the PIC so as to achieve a good efficiency. When the control system is refined, connect it to a BIG transformer + SS relay.

 

Sounds like a fun project. It'd be especially useful for guys who work with shrink fits, or melting small quantities of metal.

Edited December 15, 2008 by Swede

[rev.redneck]

You do not exactly need all of That. It is possible with Spark gaps. I used three MOT's with Cap's, But its not as safe!

[mormanman]

If your serious about induction heating which I doubt you are ask around on sciencemadness a member there 12AX7 is into this kind of stuff.

If its not too expensive to DIY then hell yes I would do it.

 

I get to learn TIG next Tuesday. Its going to be sweet. I'll probably be the only person at school that can TIG. My shop teacher can't do it. He's never tried but he can Oxy weld and the seem similar.

[tentacles]

I've seen kitchen type inductive hotplates - I wonder if you couldn't bastardize one of those for your evil plans? They usually run about 100 bucks on ebay.

[_DB_]

Decided to stop by here for the first time in months. The new look of the forum really caught me off guard!

 

Man am I behind...

[mormanman]

I thought I was behind after a couple weeks.

Sweede, I looked there and didn't find much.

[asilentbob]

Mormanman, you just sent a mass email (with attachment) to what looks to be all your email contacts, including many who obviously would not be interested. IE skylighter. If you didn't do this on purpose, I'd recommend you scan for virii/worms/etc now, and with multiple programs.

 

Bleh, been busy with things other than pyro lately. Mostly more electronics related. Looks like I'm going to throw myself into PIC microcontrollers by trying to copy someone elses work without a really solid tutorial or anything, just sorta going by what info he provided... Going to try to make a frequency counter... complete with 7 segment LED displays, 4 or 5 of them. This is a good deal more advanced than anything I should rightly attempt... but meh, its a learning experience and the parts I think I need are on the way already... Going to do it on prototyping board... ya know the PCB with little holes evenly spaced with little copper clad rings around each one... Will most likely incorporate it into a small HAM radio project...

 

Got some of my old un-used music equipment on consignment today, finally. So hopefully I'll get a bit more pocket money soon.

 

Don't know what I'll do tomorrow. Maybe work on the star roller yet again... Maybe clean up the garage some... dunno.

[WarezWally]

I lost an important bolt off my mini lathe when I was stripping it down and cleaning it, its one of two bolts that hold the compound to the cross slide. Subsequently when I go to take a cut the pressure pushes the compound away making it impossible to make a accurate cut.

 

I don't think the bolt is a standard size I can pick up easily, might have to buy an M3 bolt and cut it.

Edited December 17, 2008 by WarezWally

[tentacles]

Wally: That bolt ought to be a standard metric socket cap screw - I'd try an industrial type hardware store or just a very good hardware store. Somewhere that has a million little bins of odd parts and fasteners should have something close enough. Otherwise, the down under equivalent of McMaster, Grainger, MSC would be a solid bet. If you do end up having to shorten a fastener, be sure to thread on a nut, then grind/cut off the extra portion, then clean up the cut, and when you unscrew that nut it will work wonders for cleaning the threads up so you can actually thread the damn thing in.

[Richtee]

Hypothesis: For the money James B. Beam is the best bourbon available. Please discuss... if yer old enough ;{)

[Frozentech]

Hypothesis: For the money James B. Beam is the best bourbon available. Please discuss... if yer old enough ;{)

 

Maker's Mark, no contest. Jim is nice, but almost generic in comparison. If you have the money to spend, there's a few other single barrel and small batch bourbon's that would make a nice Christmas gift.