Re: [DIYbio] open source syringe pump

On 09/25/2014 04:50 AM, jem wrote:
> I think being able to shut off the tip of the syringe is the only way to stop drips, and I have a few ideas about that. :-)

Nordsen EFD does too -- it's a mature product with a lot more complexity than "retract to control drips".
EFD valves cost thousands, and Chinese copies of off-patent versions cost $250 each.

Doing a little extra "control" work, with sensor inputs and a direct syringe drive with short stiff
luer-lock tips may get close to "dispensing valve" performance with a price low enough for rows of them.
I'm thinking of bio-printer apps for the "rows of them".

With the concept of small footprint, (all the dispense machinery in a small area vertically from
the dispense tip), and rows of them mounted on a X-Y carriage, you could load up several media
to dispense, and load up more of the ones you need more of. Each syringe would need to be movable
vertically some distance for clearance so only one is low for dispensing and the others
don't interfere with the surface you are printing on.

A tip shutoff flap of rubber would be a good thing -- not for use until you want to park that tip.
Such a solenoid operated flap valve would be for the purpose of stopping drying, curing,
degrading in air, etc. Using such a simple external flap valve could be done whenever the tip is
moved up rather than closing the output stream with a needle valve from inside.

It's complicated. It will need lots of testing and always have a messy potential
and be difficult to keep sterile. Long output tubes flowing pastes will tend to be drippy.

I think the syringe pump part can be cost reduced effectively though, and that has many more apps
than bio printers. Something that needs to come along with a non-dripping syringe drive
is sterilizable or throw-away-sterile tubing ports for pressure sensing. If you can sense
pressure in long paths, you can control pressure and flow.

Has anyone ever seen
a luer-lock fitting with a diaphragm seal to another port besides in and out? With a thin
diaphragm, one could measure and respond to pressures in long tubes, microfluidic passages, etc.

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