[DIYbio] Re: DIY Liquid Handler

On Sun, Aug 21, 2011 at 8:29 AM, John Griessen <john@industromatic.com> wrote:
> On 08/20/2011 03:58 PM, mad_casual wrote:
>>
>> On Aug 20, 10:41 am, John Griessen<j...@industromatic.com> wrote:
>>>>
>>>> On 08/19/2011 11:47 AM, mad_casual wrote:
>>>> Between myself and the support engineers I work with, there are some
>>>> CENTURIES
>>>> of instrument up time without having to decontaminate/change a single
>>>> line (admittedly we don't run PCR directly on the instrument, but we
>>>> do culture and DNA test off of samples after they've been analyzed).
>>>
>>>
>>> Would like to hear more on that...
>>
>>
>> Hear more on what? It's relatively routine in a hospital to do split
>> sampling or post hoc analysis. I
>> think either I've mistakenly over-glorified something or you've
>> misinterpreted what I'm saying.
>
>
> I'm just ignorant-but-listening.
> Thanks for the long reply to my get-up-to-speed questions.
>
>
>>> This is really helpful for my thinking coming from my control system
>>> analog
>>> and systems engineering experience. I had been thinking that in-tubing
>>> analyzer systems would not work with a chance of getting an active
>>> molecule
>>> of DNA or enzyme or RNA stuck to a tubing wall, but you are clarifying to
>>> me that you can. They just get washed out by a flow of cleaning water or
>>> ??
>>
>>
>> This depends on the scale of the application. All the tubing I've
>> pointed to just moves air, as long as the tubing is relatively uniform
>> and/or stable in temperature it doesn't make a lick of difference.
>> Most of the microarray robots I've worked with in the past used hard
>> plastic, teflon, or stainless 'nozzles' and those were dispensing at
>> the tens (or less) of nano-liter level.
>
>
> Hmmm... Let me try out a scenario of automated culture growth and storage:
>
> Incubator includes cuvette agitation and light transmission measurement to
> decide
> when enough growth has happened. Liquid handler snap on module can dispense
> into cuvette, wash and UV sterilize its liquid handling tubing length, draw
> out
> of cuvette and move tip out of incubated zone
> to a refrigerated zone, and temperature control its own tubing for as
> far as any drawn in liquid goes.
>
> This system app is slow -- plenty of time to "do stuff", wait,
> repeat-while-necessary.
> Would 50 ul max capacity to draw in liquid allow tens of nl accuracy?
>
> If so, I can see a module to snap onto an incubator and also as a plate prep
> robot, even though they have a big difference in required volumes handled.
>
> As you prepare to draw in liquid do you put a volume of wash water
> separated by an air bubble (or several),

From what I've seen, a lot of tiny fluidics like to avoid air like the
plague. I've seen droplet fluidics using oil to separate samples, but
the paper this video links is using air and water to separate samples,
and it shows in-system mixing
https://www.youtube.com/watch?v=AENnU0vdjPo

Usually problems with air are more significant as you get smaller,
here are the sizes that video used:
"The flow channels consisted of a main flow channel and a handling
flow channel branched from the main flow channel. The width and depth
of the former were 600 and 200 μm, whereas those of the latter were
200 and 200 μm, "

http://diyhpl.us/~bryan/papers2/paperbot/Microprocessing%20of%20Liquid%20Plugs%20for%20Bio_chemical%20Analyses.pdf

--
-Nathan

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