Re: [DIYbio] Re: Cheapest and easiest way to do PCR at home?

Thankful for your advices.
Ms

Il 21/set/2014 20:40 "John Griessen" <jo...@industromatic.com> ha scritto:

On 09/20/2014 05:44 AM, Michele Stefanoli wrote:

So thermal inertia is the issue. Would a 250W Ir lamp be the solution cooling up faster?

Many cyclers down the ages, (last twenty years), have used mechanical means to
switch hot cold quickly.  They break the heat flow path by movement.  A cam moves the thermoelectric
cooler heat sink out of contact with the samples-heater-block, then heaters turn on, heaters turn off,
cam moves back.

250 Watts?  Depends on mass of samples/heat sinks/etc.  Could easily be smaller.  Could be a hair dryer
at 1000 Watts as well like Nathan suggests.

Air as the samples contact medium is the easiest way to switch heat flow back and forth if you ask me.
Think of "any kind of hot air source" blowing all the time, and a light weight door in a Y branch
in the air path to switch the air stream into the samples area or bypass it.  Another ambient air
blower feeds another air path with  Y branch flap valve to choose cool ambient air into samples
area or bypass.  Next you just control the movement of these valves on the air ducts to
get thermal cycling.  Use sensors at the heater box and at the samples zone
to tell how close to desired temperature you are.  Preheated air flow needs to be fast
and wide swirling past your sample vials to get even and rapid heat transfer.

Recycle hot air that has either gone through the samples area or been bypassed around it to the intake
of your heater box to save energy.  Let a separate control system regulate the heater to keep the
heater box exhaust at a reasonable temp you determine to get good heat flow rates.
Maybe the preheated air temp will be 140 deg C, maybe 118 deg C, maybe 180.

Testing will tell.

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