Hi Jake,
I haven't crunched the numbers yet, have you? I can assure you aluminum is generally
a great material for heatsinks and sheds heat very quickly. I've done butt welds on
1/2" aluminum plate that were cool to the touch by the time I took my glove off. It
has about a quarter the heat capacity of water so will pass on heat very quickly. I would
start with aluminum strip unless you have some gold or silver you want to donate. The
tooling and the machine are both available, and it's also incredibly easy to machine
and may not even require coolant depending on the cut, for the same reason noted above,
and has a pretty low melting temperature easily attainable with a blowtorch. So it's
a good material for the application, can be machined easily to the desired shape, and if
testing shows that the amount of material required for the machined version has too much
thermal mass for the wattage we think is reasonable, going the next step and casting it
will not require too much specialized equipment other than a pattern, some casting sand, a
crucible, and a blowtorch. I'm not sure what the cost would be to have these things
printed in sufficient resolution, or how the 3D printing process affects the porosity and
thermal properties of the part. The presence of air between the peltier element and the
wells would be more likely to insulate, probably more than offsetting your thermal mass
savings.
Cheers,
Hol
Aug 21, 2013 04:44:56 PM, jake(a)spaz.org wrote:
I think part of the problem with that is that if you want to make your
openPCR do the job in a reasonable time frame, you need
to be able to
thermally cycle your fluids rapidly.
every bit of material you have that is thermally connected to the PCR
vials and heating/cooling apparatus is thermal mass that you need to
swing, which makes your energy demand greater on your heat pump, and/or
slows down your PCR time.
that's why the best material for touching the vials will likely be a thin
skin of aluminum, shaped like inverted cones on one side and flat surfaces
on the other side, but mostly hollow. Such a shape would be designed in
openSCAD, modeled with a 3D printout, and either cast at OMI or Jim's or
Bernards, or more likely ordered as a metal print from Pomoko or Shapeways
or something.
unless you don't care about PCR time, in which case yes, you can make your
own thermal manifold out of a block of aluminum or lead.
-jake
Aug 21, 2013 01:58:57 PM, patrikd at
gmail.com wrote:
Hi Hol,
Why don't you guys use Hackteria's drill bit to drill the wells in the
aluminum heat block? They designed and ordered a custom bit specifically
to match the 17.5 degree cone angle used in OpenPCR, and they're willing
to let other groups borrow it. Perfect example of leveraging the global
DIY community!
http://hackteria.org/wiki/index.php/Wild_OpenPCR
Simon Field on the DIYbio list suggested a while back to cast the heat
block from a lower-melt alloy. That's potentially something that anyone
with a hot plate could achieve, and you could even use your own favorite
PCR tubes to make a perfectly fitting mold.
Patrik
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Aug 21, 2013 04:44:56 PM, jake(a)spaz.org wrote:
I think part of the problem with that is that if you want to make your
openPCR do the job in a reasonable time frame, you need
to be able to
thermally cycle your fluids rapidly.
every bit of material you have that is thermally connected to the PCR
vials and heating/cooling apparatus is thermal mass that you need to
swing, which makes your energy demand greater on your heat pump, and/or
slows down your PCR time.
that's why the best material for touching the vials will likely be a thin
skin of aluminum, shaped like inverted cones on one side and flat surfaces
on the other side, but mostly hollow. Such a shape would be designed in
openSCAD, modeled with a 3D printout, and either cast at OMI or Jim's or
Bernards, or more likely ordered as a metal print from Pomoko or Shapeways
or something.
unless you don't care about PCR time, in which case yes, you can make your
own thermal manifold out of a block of aluminum or lead.
-jake
Aug 21, 2013 01:58:57 PM, patrikd at
gmail.com wrote:
Hi Hol,
Why don't you guys use Hackteria's drill bit to drill the wells in the
aluminum heat block? They designed and ordered a custom bit specifically
to match the 17.5 degree cone angle used in OpenPCR, and they're willing
to let other groups borrow it. Perfect example of leveraging the global
DIY community!
http://hackteria.org/wiki/index.php/Wild_OpenPCR
Simon Field on the DIYbio list suggested a while back to cast the heat
block from a lower-melt alloy. That's potentially something that anyone
with a hot plate could achieve, and you could even use your own favorite
PCR tubes to make a perfectly fitting mold.
Patrik
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