Re: [DIYbio] titanium: "boils water definitely twice faster then any Al cups" -- can it be?

On 12/19/2017 07:28 PM, Nathan McCorkle wrote:
> Exploring the limits of ultrafast polymerase chain reaction using liquid for thermal heat exchange: A proof of principle
> Appl. Phys. Lett. 97, 264101 (2011); https://doi.org/10.1063/1.3530452

And here's the juicy details of heat transfer:


"Our thermal cycler, Fig. 1, used a liquid interface sand-
wiched between two high-powered Peltier devices,
(Marlow XLT2393, Dallas, TX), that worked in tandem to cycle the
temperature rapidly. They rejected waste heat to a pair of
fan-cooled heat sinks. These high efficiency heat sinks were
sized to allow for increased cooling rates due to their ability
to bias the heat exchange toward lower temperatures, opti-
mizing power usage at less than 400 W. A phenolic gasket
held 2.3 ml of thermal transfer medium, (gallium eutectic),
between the two face surfaces of the Peltiers, making direct
thermal contact between them and the sample capillary tube.
The liquid allowed for excellent thermal contact to the glass
capillary tube. The small volume needed to make thermal
contact required less than 200 J to raise the medium's tem-
perature from 60 to 95 °C. In a typical thermal cycler, the
thermal resistance between the junction of the solid metal
block and the sample tube is a dominant factor in reducing
the ability to transfer heat in and out of the sample, resulting
in slow thermal cycling."

See how they key on, "required less than 200 J"?

Losing the air gap between solid blocks with thermal mass
is a speed up.

My plan to do air PCR with movable doors will allow quick
change from heating to cooling without need to switch the direction
or even on/off state of a Peltier cooler, so any thermal mass
built into the cooler that slows switching between heating and cooling
will have no slowing effect using air and movable doors.

The airpcr air will be the only medium of transfer of heat between hot nichrome
heater element wires and sample tubes. It will be moving fast to
give complete stirring for even temperature, and quick heat transfer.

Still busy with electroporation, but stay tuned.

--
John Griessen
industromatic.com Austin TX building lab gear for biologists

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