Re: [DIYbio] Re: At home fabrication of micron scale microfluidics

My co-worker has a formlabs printer, it seems pretty decent... The Z
direction sounds good, but I imagine it could be obviated by the use
of a spin-coater. They say their minimum feature size if 300microns...
I was thinking about this recently actually and ran into the
laserShark galvanometer controller. I think the main thing that would
need to change for great microfluidics with this type of setup is
really just the per-bit voltage-interval... i.e. if the DAC on the
galvanometer controller is 16-bits spanning the form1 build dimensions
of "125 × 125 × 165 mm"... then the range of millimeters spanned needs
decreased. If it's a linear decrease, then if I wanted a max
microfluidic X/Y dimension of 30mm, that's 125/30==4.166 then
300/4.166==72 microns resolution. Maybe their DAC is not enough bits,
or maybe this technique is not optimal, I don't know. It could simply
be that the long path that the beam passes takes, leaving the laser,
bouncing off the galvos, is just too much from a beam divergence
standpoint. To get a small spot size with such focal distances, I
think the laser would need a pretty big beam expander before lensing
onto the first galvo.

On Sat, Feb 28, 2015 at 3:52 PM, Otto Heringer <ottowheringer@gmail.com> wrote:
> I always wanted to print a mold for PDMS microfluidic chips using a "form 1"
> 3D printer (that one who got funded on kickstarter). They say that it have
> 10 microns of resolution on Z axis.
>
> When I was about to try it on a local FAB Lab, the printer got broke! If it
> was worked out, I would suggest to consider a 3D printer for the molds.
>
> I think its about time for people go for digital fabrication methods on
> microfluidics.
>
> Em 27/02/2015 21:17, <scocioba@gmail.com> escreveu:
>
>> This is true, only issue there was when using a syringe to pull from chip
>> to chip, the line would sputter and induce air pockets on top of very swift
>> changes in fluid flow once it gets past the bottleneck that is the chip.
>> There is a lot of resistance since the channel features are so small that
>> manual pull is to quick. Need a syringe pump in reverse that pulls slowly.
>>
>> Like filling a syringe quickly with liquid through a very small needle, it
>> bucks back until the liquid meets the top of the plunger (vacuum until
>> pressure equalizes) so either way fine, non-manual control would be ideal.
>> Backpressure is too high for standard cheap-o eBay peristaltic pumps in
>> either direction. Basically its analogous to electronic theory...small
>> channel, high resistance. Syringe acts as a voltage source trying to pull
>> more than the channel can deliver so its either slow or the channels (or
>> chip) fails structurally.
>>
>> For the few moments when the pdms is perfectly bonded via coronal arch
>> discharge and everything is aligned properly, I did get some plant
>> protoplasts stuck in a T junction for a while while flowing media through.
>> Its possible, just really really finicky.
>>
>> On my laundry list of experiments to run, I'd like to do some data
>> gathering on the characteristics of shrinky dink plastic sheets,
>> temperature, shrink rate (~63%), etc to see if its a viable material for
>> making multiple fairly-identical chips. Basically a datasheet characterizing
>> the material within the scope of microfluidics. May prove useful to people
>> trying to start working with microfluidics.
>>
>> Sebastian S. Cocioba
>> CEO & Founder
>> New York Botanics, LLC
>> Plant Biotech R&D
>> ________________________________
>> From: John Griessen
>> Sent: ‎2/‎27/‎2015 6:46 PM
>> To: diybio@googlegroups.com
>> Subject: Re: [DIYbio] Re: At home fabrication of micron scale
>> microfluidics
>>
>> On 02/27/2015 05:29 PM, Simon Quellen Field wrote:
>> > The alternative that suggests itself is to pull the liquid from one
>> > block to another using a relative vacuum. Now the liquid wants
>> > to go only where you want it to go.
>>
>> because vacuum makes contact seals seal harder, and pressure makes them
>> leak.
>>
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--
-Nathan

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