A commercially manufactured thermostat (Model C Thermostat, Portage Electronic Products Inc., North Canton, OH) was employed as a precision MEMS temperature controller for a simulated continuous flow thermal reactor, with three temperature zones to mimic a polymerase chain reaction (CFPCR) device but different temperature set points to allow use of off-the-shelf controllers and thermally-responsive fluids. The ability of the commercial thermostats to maintain the temperatures within given tolerance bands in the thermal reactor was investigated. The factory supplied and calibrated thermostats were actuated by trimetallic strips, and supplied in a normally-closed configuration. Each thermostat was arranged in series with a 28 VDC power supply, a Kapton heater, and an aluminum thermal block to establish a constant temperature boundary condition for each temperature zone. Calibration temperatures for each thermostat reflected the three temperature set points of the simulated PCR device in the testing apparatus. Temperatures were collected by fixing Type K thermocouples in the fluidic channels of the simulated PCR device, and recording the temperature over time. The commercial, off-the-shelf, open-loop controllers successfully maintained ±1°C tolerance bands within each thermal zone. The ±1°C variation in the channel temperature was caused by the chatter due to the switching of the thermostat.
Design and development of polymerase chain reaction thermal cycler using proportional-integral temperature controller