Digital Designs and Scientific Hardware - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 229

ensures that condensation is prevented, thereby improving your results by ensuring that your
reagent concentrations remain correct throughout the cyclical process—just as high-end PCRs
do. If this was a closed, commercialized PCR and you were unhappy with the features, you
could call and complain to the company, go shopping again, or start from scratch and build
one yourself. That is not a very good range of options. However, as with all OSH tools, with
the OpenPCR, you can change or enhance it to meet your specific needs—the “activation en-
ergy” to build on the already created open design is much less than that to start from scratch.
OpenPCR has already been hacked to do microfluidic PCR, and software has been written for
complete laboratory automation.
6.5.2 Open-source centrifuges
A laboratory centrifuge is used to spin liquid samples at high speeds and has many applica-
tions in a range of different types of biological laboratories. Centrifuges work using the sed-
imentation principle, where the centripetal acceleration causes denser substances to separate
out along the radial direction (e.g. for particles to collect at the botom of the tube). There are
many types of centrifugation, which are useful in the laboratory including (1) differential cent-
rifugation, which can separate certain organelles from whole cells for further analysis of spe-
cific parts of cells; (2) isopycnic centrifugation, which is used to isolate nucleic acids such as
DNA; and (3) sucrose gradient centrifugation, which is used to separate cell organelles from
crude cellular extracts and to purify enveloped viruses and ribosomes. Microcentrifuges tend
to be the most useful in a lab as they are designed for small tubes able to hold from 0.2 to
2.0 ml (micro tubes). In general, these small devices can obtain up to 30,000 g (where g is the
acceleration due to gravity at the Earth's surface). Protocols for centrifugation normally speci-
fy the amount of acceleration to be applied to the sample, rather than specifying a rotational
speed such as revolutions per minute (RPM), which is useful because it enables protocols to
span different devices with various rotor lengths. The relative centrifugal force [ g ] applied to
a sample in a centrifuge is given by Eqn (6.3) :
(6.3)
where r is the rotational radius in centimeter and s is the rotational speed in RPM. Here, we
will briefly outline several types of open-source centrifuges.
6.5.2.1 DremelFuge
Of all the open-source centrifuge designs, the DremelFuge is perhaps the most elegant. The
DremelFuge (as shown in Figure 6.71 ) is a printable rotor for centrifuging standard micro-
centrifuge tubes and miniprep columns, which uses a high-speed drill or Dremel tool to spin
down samples as shown in Figure 6.72 . 70 The Dremelfuge was developed by Cathal Garvey in
Ireland to assist in his research with DIYbio. 71