idea for microfluidic valving

[Nathan McCorkle]

these valves work on pneumatic/hydraulic pressure, basically like
stepping on a water hose to stop the flow.
http://www.stanford.edu/group/foundry/Microfluidic%20valve%20technology.html

if one would want to control hundreds or thousands of valves at a
reasonable cost... I'm wondering if you could acquire small hollow
electromagnets to use as a solenoid directly on the membrane, or as a
single-channel displacement pump.

I'd like the cost per valve to be about $1-1.50 USD. It seems like
these would work but @$3-4 per valve
http://www.ebay.com/itm/Miniature-ODV76-L92121-P2-Linear-Bi-Directional-Stepper-Motor-12VDC-/110810764668?pt=LH_DefaultDomain_0&hash=item19ccd6157c#ht_758wt_1037

I feel like Simon could really chime in with some good perspective on
this, is this something that would be low enough force that I could
wind the coils and build all the tiny solenoid/pumps?

--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics

[CoryG]

I was playing around with NiTi springs + steel wire (attached to the
end of a spring, formed into a loop) to control the flow of microbore
tubing by crimping it with the loop of steel wire awhile back. Pretty
cheap, need to include a temperature sensor with the NiTi spring to
prevent it from overheating or keep it submerged in water - other than
that, they run about 5-20 cents (depending on sources of tubing and
NiTi) a piece in parts - and have the potential to control multiple
tubes in a single valve.

On Jan 23, 2:52 am, Nathan McCorkle <nmz...@gmail.com> wrote:
> these valves work on pneumatic/hydraulic pressure, basically like

> stepping on a water hose to stop the flow.http://www.stanford.edu/group/foundry/Microfluidic%20valve%20technolo...

>
> if one would want to control hundreds or thousands of valves at a
> reasonable cost... I'm wondering if you could acquire small hollow
> electromagnets to use as a solenoid directly on the membrane, or as a
> single-channel displacement pump.
>
> I'd like the cost per valve to be about $1-1.50 USD. It seems like

> these would work but @$3-4 per valvehttp://www.ebay.com/itm/Miniature-ODV76-L92121-P2-Linear-Bi-Direction...

[Chris]

@Nathan here are some tiny hollow magnets:
http://www.scitoyscatalog.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BEADMAGNET&Category_Code=M

As far as cheap coils, I would look at inductors at a place like
digikey: For example http://search.digikey.com/scripts/dksearch/dksus.dll

Another route to go would be to have one 'master actuator' they moves
between the valves and switches each unit individually with a 'passive
switch' to a certain state as opposed to having each valve
addressable.

Just a thought...
Chris

On Jan 23, 2:52 am, Nathan McCorkle <nmz...@gmail.com> wrote:

> these valves work on pneumatic/hydraulic pressure, basically like

> stepping on a water hose to stop the flow.http://www.stanford.edu/group/foundry/Microfluidic%20valve%20technolo...

>
> if one would want to control hundreds or thousands of valves at a
> reasonable cost... I'm wondering if you could acquire small hollow
> electromagnets to use as a solenoid directly on the membrane, or as a
> single-channel displacement pump.
>
> I'd like the cost per valve to be about $1-1.50 USD. It seems like

> these would work but @$3-4 per valvehttp://www.ebay.com/itm/Miniature-ODV76-L92121-P2-Linear-Bi-Direction...

[Nathan McCorkle]

On Mon, Jan 23, 2012 at 11:27 AM, Chris <christe...@gmail.com> wrote:
> @Nathan here are some tiny hollow magnets:
> http://www.scitoyscatalog.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BEADMAGNET&Category_Code=M
>
> As far as cheap coils, I would look at inductors at a place like
> digikey: For example http://search.digikey.com/scripts/dksearch/dksus.dll
>

Thanks, I'll try to find some examples of people using small inductors
as a solenoid.

> Another route to go would be to have one 'master actuator' they moves
> between the valves and switches each unit individually with a 'passive
> switch' to a certain state as opposed to having each valve
> addressable.
>
> Just a thought...

Not a bad thought, actually... I hadn't considered that, it wouldn't
allow simultaneous switching, but I haven't considered whether that
would be required or not (my instinct is probably I would want
simultaneous operation)

> Chris

[Jonathan Street]

Do you have a schematic or photo of this?  It sounds interesting but I'm not sure I'm visualising it correctly.

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[Bryan Bishop]

On Mon, Jan 23, 2012 at 1:52 AM, Nathan McCorkle <nmz...@gmail.com> wrote:

if one would want to control hundreds or thousands of valves at a
reasonable cost... I'm wondering if you could acquire small hollow
electromagnets to use as a solenoid directly on the membrane, or as a
single-channel displacement pump.

1000s of valves is a nightmare, especially as a routing problem... How about something like, optical addressing.

Single-sided continuous optoelectrowetting (SCOEW) for droplet manipulation with light patterns

http://diyhpl.us/~bryan/papers2/microfluidics/Single-sided%20continuous%20optoelectrowetting%20(SCOEW)%20for%20droplet%20manipulation%20with%20light%20patterns%20-%20LCD%20-%202010.pdf

Massively parallel manipulation of single cells and microparticles using optical images

http://diyhpl.us/~bryan/papers2/microfluidics/Massively%20parallel%20manipulation%20of%20single%20cells%20and%20microparticles%20using%20optical%20images%20-%20DMD%20mirrors%20-%20Chiou,%20Ohta,%20Wu.pdf

- Bryan
http://heybryan.org/
1 512 203 0507

[Simon Quellen Field]

I would have come in earlier, but I was at a 3 week workshop.

If you want to do thousands of valves on a DIY budget, each valve

should cost pennies or less. The Nitinol solution comes close, and

is worth pursuing, but building a thousand of them sounds tedious.

Suppose you have a PDMS sheet above a network of channels, so that

pushing down on the sheet above a channel cuts off the flow.

Now spread some glue on top, and sprinkle with magnetic sand, made

from the same stuff NdFeB magnets are sintered or bonded out of.

Now you can move an electromagnet under it on an X/Y table, and

turn the magnet on to pull the sand down on the PDMS sheet.

A neat trick is to make two combs out of mild steel pins, each with 32 teeth. The teeth are separated by non-metallic plastic, aluminum, or brass.

The two combs are orthogonal to one another, in an X/Y arrangement,

and one below the other. You move the combs so that one tooth from

each comb is under the PDMS valve you want to control. An electromagnet

under the combs is then turned on. The steel pins conduct the magnetism,

so that only the sand above both teeth is pulled down. The electromagnet

is not strong enough to pull down any of the sand without the flux 

concentration that the pins provide.

Of course this only gets you one valve at a time.

One comb moves in the 

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[Nathan McCorkle]

Hmm, so you were actuating the springs with heat?

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[Forrest Flanagan]

@CoryG

The temperature of the NiTi may be read directly by measuring the resistance, V/I.

[Jonathan Cline]

On Sunday, January 29, 2012 12:53:20 PM UTC-8, Simon Field wrote:

Suppose you have a PDMS sheet above a network of channels, so that

pushing down on the sheet above a channel cuts off the flow.

Previously I thought dot matrix printer heads could be explored here.  Though never did the calculations for required displacement.  I'm sure some printer heads move several mm's for imprinting in carbon paper (just guessing).  With 12 or 24 pins per head (or more?), that might yield control over a couple of intersections depending on channel size and density.   Cost might be cheap or free.  Solenoids use a good amount of current and require maintaining the current in the forced position, so could result in problems with power & heat at high densities.  And don't get liquid in or on the head or it will likely jam & need cleaning - but otherwise that technology is rock solid.


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