MJ Research PTC-0200, Operation Manual

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B-1 B-1 B-1 B-1 B-1
The functional heart of every DNA Engine is a high-performance Peltier-effect heat pump (also
known as a “thermoelectric module”). This solid-state device is manufactured to withstand the
thermal stresses associated with rapidly cycling temperatures.
A thermoelectric module consists of numerous pairs
of crystalline semiconductor blocks precisely sand-
wiched between two layers of ceramic substrate (fig.
A-1). The blocks are of two varieties: “N-type,” which
has a surplus of electrons in its crystalline structure,
and “P-type,” which has a deficit of electrons. The two
types are positioned in alternating pairs within the in-
nermost layer of the sandwich.
The two types of blocks are wired together in alternat-
ing pairs. When electrical current is passed through the
blocks, electrons in the N-type blocks and the “holes,”
or empty electron spaces, in the P-type blocks are ex-
cited at one conductor-semiconductor interface, which
absorbs a small amount of heat. The electrons and holes
flow through the crystalline blocks and return to a low-energy state at the other conductor-semi-
conductor interface, with the release of the previously absorbed heat. A thermal gradient of up to
70
°
C can be generated across the blocks in this manner.
The direction of heat pumping is reversed by reversing the polarity of current flow through the
thermoelectric module, and the amount of heat pumped is changed by changing the amount of
current passed. Both direction and amount of current flow are dictated by a microprocessor in the
Alpha unit, allowing precise control of thermal cycling in the Alpha unit block.
How a Peltier Heat Pump Works
Appendix B
Electron
Hole
N-type
bismuth
telluride
N-type
bismuth
telluride
Metal conductor
P-type
bismuth
telluride
Ceramic substrate
Power input
Power input
Figure A-1 A thermoelectric module.