Re: [DIYbio] Re: Low cost PCR(under development)

If you are only planning on small fragments, what about these approaches:

http://www.biotechniques.com/BiotechniquesJournal/2011/January/Rapid-DNA-amplification-in-a-capillary-tube-by-natural-convection-with-a-single-isothermal-heater/biotechniques-307538.html?pageNum=1
http://www.sciencemag.org/content/298/5594/793.full
http://www.jove.com/video/2366/rapid-pcr-thermocycling-using-microscale-thermal-convection

-Dave


On Tuesday, July 1, 2014 5:06:55 PM UTC+2, Cathal Garvey wrote:
> Yep, think about a hair drier. I also have a hot air PCR
> thermocycler... it uses a light bulb for a heater... but didn't seem
> to have a great ramp rate.

Yea, this; I was going to compare a heat gun to an oven. Air has very
low heat capacity, so it delivers heat in tiny doses, then tends to form
a "cusion" of cooled air around the object. So, ovens are less burn-ey
than a heat-gun for the same temperature; the latter blasts away the
cooled air-shell and replaces it with high-temperature air constantly.

I knocked together a hot/cold air thermal-cycler using a coffee can,
computer case fan, and an art-grade heat gun once. I used an LM35
temperature sensor and suspended samples within the can. At least as
read by the LM35, which was within a sample vial for "realism", ramp
rates of 3-5C either way were achievable by hot/cold air.

Bonus; when dealing with total-immersion fluids like air, you shouldn't
need to worry much about oil or heated lids, because the whole tube will
be heated/cooled simultaneously. If you found that you did have
problems, putting dollops of insulating material on top would probably
suffice to stop the lids cooling fast enough to deposit vapour; silicone
tube beanies! :)

On 01/07/14 03:07, Nathan McCorkle wrote:
> Yep, think about a hair drier. I also have a hot air PCR
> thermocycler... it uses a light bulb for a heater... but didn't seem
> to have a great ramp rate.
>
> For modifying a hair drier heater coil to be arduino-controllabe,
> these two instructables should be useful:
> http://www.instructables.com/id/Extreme-Surface-Mount-Soldering/step1/Order-Parts/
> http://www.instructables.com/id/Closing-the-Loop-on-Surface-Mount-Soldering/
>
> they don't include snubbers, so couldn't be used to control the fan
> motors, but it will work for the AC heater component which is going to
> be higher amperage than the fan(s) anyway.
>
> On Mon, Jun 30, 2014 at 6:48 PM, Cory Tobin <cory....@gmail.com> wrote:
>> Actually, I take back what I said about air not transferring heat to
>> the sample very quickly.  I remember a device a long time ago, I think
>> it was called the "Indee" or something like that, that used really hot
>> air and circulated it around the tubes really really fast.  I think
>> the ramp rate was around 8C/s.  They basically made up for the poor
>> thermal conductivity by heating the air up to like 200C and then
>> bringing it back down as the calculated sample temperature reached the
>> target temperature.  Which made it faster than the peltier devices.
>> So maybe air wins out in both cost and speed if designed right.
>>
>> -cory
>>
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