The cost breaks down about three ways:
1. Off the shelf components - there is no single obscenely expensive
component of the OpenPCR, but a lot of moderately expensive and even
inexpensive components that add up. You can find cheap temperature
sensors for $1, but these don't have the accuracy and dynamic response
that are required for OpenPCR's 0.5C accuracy. It's the same for a lot
of the components you mention and the other components in the BOM. For
example the specifications of the peltier are hardly any "decent"
peltier. Most peltiers on ebay are used for CPU cooling which are not
suitable for thermocycling. The PSU is capable of 12 A at 12 V. etc.
Even if you add up the McMaster-Carr components, that produces a hefty
bill.
2. Custom components - there are a handful of custom components in the
BOM, and it is very expensive to get these made in the small
quantities needed for the OpenPCR kits. Getting them machined properly
required a lot of back-and-forth prototyping with different
manufacturers. The block is made from 1100 aluminum which is difficult
to machine and most online machine shops don't even offer it.
3. Fulfillment - the whole purpose of providing OpenPCR kits to the
community is to collectively reduce costs by ordering in bulk and
redistributing to individuals. There is a lot of time and money spent
on finding suppliers, ordering, paying shipping and duty, inventorying
components, packaging the 211 total components (83 separate BOM items)
into individual baggies and boxes, accepting online payments, and
shipping out. Many of those components are actually modified by us
because required tools are not readily available. For example the USB
chip on the Arduino is reprogrammed using a hardware programmer. All
of this fulfillment takes an insane amount of work. Those who ordered
OpenPCRs early on knew we had some significant delays in fulfillment,
which was the result of figuring out how to do all of this and ramping
up our capacity. Plus, being a kit, we have to provide a lot of
post-sales support - people may assemble something wrong and require a
replacement part, etc.
I've thought about producing a cheaper design for a while and have
some ideas of how to do it, starting with removal of the heated lid
(which also, many of these cheap ebay units don't have). I haven't
moved on it mainly because I'm not sure it would be very
transformational. If people want to do PCR on a budget, it is already
possible with 3 pots, 3 burners on a stove, 3 thermometers, and some
time. This is the first way I did PCR at home. A PCR machine brings
automation. The purpose of automation is to trade money for time.
Before OpenPCR there were already a range of automation trade-offs
available, ranging from $300 used ebay units to $10,000 new units. I
didn't like any of those trade-offs however. I was looking for a lower
price, open design, fully functional/accurate unit, with a heated lid
(which further automated by removing mineral oil PCR steps, which
often leads to contamination, especially in some public lab classes I
was running). Thus, OpenPCR.
Now lets say there was a $200-$300 OpenPCR. Sure a cheaper machine is
always more beneficial to the community, but how much more? Would it
be worth the effort? Here is my thinking. For someone who wants to do
a small number of basic PCR experiments on a shoe-string, there are
already free or extremely low cost options (i.e. light bulb PCR
discussed previously on this list), so they have choices if the $600
OpenPCR is an obstacle (they can also go to a community lab/community
college if they have nearby). For someone who wants to do some serious
experimentation on an on-going basis (like the guy who wanted to do
chicken parentage testing I referred to this forum), you are going to
need more than a PCR machine (polymerase, primers, digestion enzymes,
gel/capillary electrophoresis, sequencing services, etc), so a $600
PCR machine is actually just a small fraction of the overall cost.
So rather than just making ever more cheaper PCR machines, I am more
interested in:
1. Automated machines, like a self-contained device that can
completely answer the chicken maternity/paternity question and other
such questions on its own
2. Cheaper/open versions of other lab equipment - so much of this
stuff is ridiculously expensive and no open software for - flow
cytomers, mass spec, -80 storage, fluorescent microscope, capillary
electrophoresis, microfluidic drivers, nanodrop, etc.
-Josh