copper etched microfluidics?

[Jeswin]

Anyone try this method out? I know that people etch boards for their
electronics projects at home. Doesn't seem too complicated for those
with etching materials on hand.

Low-cost, rapid-prototyping of digital microfluidics devices
http://microfluidics.utoronto.ca/papers/DMF%20by%20Marker%20Masking.pdf

[Nathan McCorkle]

Etchant can be as simple as H2O2 and HCl

--
-- You received this message because you are subscribed to the Google Groups DIYbio group. To post to this group, send email to diy...@googlegroups.com. To unsubscribe from this group, send email to diybio+un...@googlegroups.com. For more options, visit this group at https://groups.google.com/d/forum/diybio?hl=en
Learn more at www.diybio.org
---
You received this message because you are subscribed to the Google Groups "DIYbio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to diybio+un...@googlegroups.com.
To post to this group, send email to diy...@googlegroups.com.
Visit this group at http://groups.google.com/group/diybio?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.

[Jonathan Cline]

Yes, see the below.  I etched my own boards for the setup.

DIY Digital Microfluidics for Automating Biology Protocols (sub-microliter droplets)

http://88proof.com/synthetic_biology/blog/archives/280

 

Longest run of a droplet I was able to get was 7 pads before exploding or evaporating or sticking.  Be prepared to etch a lot of boards because any surface contamination or voltage fluctuation could cause arcing which will likely pit the copper edges and degrade the charge plates.  Also it is difficult to etch these boards because the pads need to have precise sizes and gaps -- that is, if you want repeatable results.  (For publishing a paper in a journal, you don't really need repeatable results or reasonable yield.. apparently.)  So it doesn't work reliably unlike as described in the paper (go figure..).  The hydrophobic surface is the difficult part, and also droplet evaporation.  Perhaps in a controlled chamber, it might be more interesting. If you have a spin coater, you can try making very thin polymer films for the PCBs.  The journal paper used a particular brand of saran wrap.  I had a few thicknesses made by the univ. chem-e lab, and they were all too thick to get good droplet movement.   There's some videos on Lab-on-a-Chip journal where a lab fabricated flex circuit ($$$) and was apparently able to get a droplet to move significant distances, the electrical switching was performed by hand (aka:  undergrad touching wires together or something).  At some point of scale really becomes a horrible routing problem of PCB traces and the only way around it is with vias and busses and.... well it might be worth it, if the method worked at all, which it doesn't, practically speaking.

You can also try the very high voltage power supply I rigged up for running the PCB, below.  (Just don't kill yourself.)  The voltage is not super accurate but neither is the humidity in a lab, ha.

HVPS for Systems Biology: A Low Cost, High Voltage Power Supply with Schematics + Board Layout

http://88proof.com/synthetic_biology/blog/archives/303

-- 
## Jonathan Cline
## jcl...@ieee.org
## Mobile: +1-805-617-0223
########################

[Marc Dusseiller]

hei all the µFluidics hobbyists...

there has already been quite a few discussions on how to make µFluidics. 

https://groups.google.com/d/msg/diybio/sM7CvT7_viA/NSBymOn04mgJ

i have been developed a whole set of home brew instructions to do so, during my activities of doing a NanoTech / µFluidics lab course for biomedical eng students.

some is here:

http://wetpong.net/wetpong/?page_id=115

http://hackteria.org/wiki/index.php/DIY_Microfluidics

http://hackteria.org/?p=1186

http://hackteria.org/?p=1508

sorry for no real documentation about the topic yet, my old wetpong wiki was uber-spammed and shut down.

the tape and cut stuff is fun, by hand as a trial or simple growth chamber. but not very reproducible.

u can also cut the tape with a laser cutter. if you dont have access to one, you can build one :-)

many tries with using etched PCBs as masters to cast the PDMS, failed, due to the fact that the substrate was too rough and it was difficult to seal the final devices. in general sealing is one of the major challenges. having a plasma chamber or gun helps:

http://hackteria.org/wiki/index.php/DIY_Plasma_generators

we are planning a DIY µFluidics Hackaton sometimes this summer, maybe in switzerland. stay tuned....

best,

marc

[Jonathan Cline]

Marc that is great info.
If I were going to experiment with the electrowetting droplet methods again, I would get a temperature controller and a toaster oven for precise fabrication and lamination of the PCB's.  Refer to the instructions on the web for inkjet PCB etching.  Add the additional step after the PCB is done, for temperature controlled lamination.  The idea is to adhere a thin film (hydrophobically coated) to the top of the PCB.  This allows the PCB to be reused and also reduces arcing (less change in resistivity of the air).

I also tried water droplets-in-oil with the technique.  Requires different voltage.  The idea is that the sample droplet (water) is encapsulated in an oil droplet. Did not have much success.  The benefit is the oil would help solve the evaporation problem.  Except then mixing becomes even more of a problem.

Droplets are difficult.  DIY time is better spent on milli-fluidics in my opinion.

[Dakota Hamill]

Some dude that moved into the incubator near me says his one man company focuses on developing new flourinated channel materials for microfluidics...I only spoke to him briefly about it but it sounded pretty cool.  Start cutting up some Teflon pans from the dollar store and make some sweet channels!  I'm going to read through your stuff later Marc it looks interesting.