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Small liquid sensing question

Small liquid sensing question

Small liquid sensing question

(OP)
I work in microfluidics and I'm looking to add leak detection to our instrumentation.

Problem:
 Basicaly our fluidic system is open until we seal our open ended silicone part onto a glass slide.  This is where I want to be able to detect any leaks.  If for whatever reason the silicone piece is not sealed correctly, (force sensing fails, other obstruction) then water and other fluids can leak and ruin other expensive parts.

-I have very little room to work with.  Idealy the sensor would mount on a small surface (0.15" x 0.40")  

Any thoughts on types of sensors?  

 

RE: Small liquid sensing question

cgmorrow,

What are the conductivity limits of the various fluids (including the water)?

Water's pretty easy to sense with just a pair of probes (which can be mighty small) to be bridged by the fluid  -- unless it's de-ionized or reverse osmosis type (super clean).  

Of course, if the "other fluids" to which you refer are combustible, you'll have to deal with creating something intrinsically safe.

Good on ya,

Goober Dave

RE: Small liquid sensing question

(OP)
Thanks for the response.  I'm acutaly setting up some tests now with some probes.  It might have to be the best option for me.  90% of the time the fluid that is in the system is salt buffers mixed with other samples, protiens, antiboties etc.  These would conduct great.  I haven't measured the conductivity yet, but the salt buffers would inherently have enough conductivity.  
The other 10% of the fluid is a de-ionized water which i'm pretty sure would not work with probes.  I will most likely go with probes unless anyone knows of another OEM small sensor for DI water.
 

RE: Small liquid sensing question

DI water that's older than about 10 minutes will dissolve CO2 from that atmosphere, and become slightly acidic.

Were it me, I'd take that entire area and generate an interdigitated probe pattern, suitably coated with gold, perhaps, to minimize corrosion, and hook up the probes to a resistivity monitor.  With sufficient probe peripheral area, even fresh DI water should be detectable.

TTFN

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