C.H.I.P: Cheap Homemade Innovative PCR
Our first design for C.H.I.P. was modeled after a more conventional PCR machine design. This first prototype used two peltier units, stacked on top of each other, to heat a customized aluminum block that sat on top of the two units and held the PCR tubes. In order for our system to have feedback, we embedded a temperature sensor in the aluminum block to detect the temperature of the wells that held the PCR tubes. The sensor then reported back to an Arduino UNO, which then regulated the energy flow to the peltier units, thereby heating and cooling the block and tubes while closing the control loop. However, after much testing, this design proved to be unoriginal, expensive, and inefficient. While the conventionality of the design itself did not pose an issue, we realized that the parts used to assemble it were not as well-known or easily accessible to the general public, which we felt would take away from the possible applications of this machine. In addition, although the price of this first prototype was relatively inexpensive in contrast to laboratory grade PCR machines, the price still ranged in the hundreds of dollars. Lastly and most importantly, the greatest issue with our design was the inefficiency of the hardware; we found that the peltier units were not able to cycle through the desired temperatures fast enough, e.g., the unit would take 5 to 10 minutes just to rise up to 95℃. After considering all of these factors, we began a redesign of C.H.I.P. to better suit the needs of the “Do-It-Yourself” market.
The idea for our current thermocycler design first came into form when we found that our original prototype was not ramping up to the desired temperatures fast enough. Because of this problem, we looked into other options for heating the machine and, in the process, disassembled a hair dryer to find out how the heating mechanism worked. To our pleasant surprise, we found that the hair dryer was able to reach very high temperatures—much higher than the desired maximum of 95℃ for PCR—in a matter of seconds. We then made a decision to suspend construction on the peltier-centered thermocycler in order to see how successful we could be and how far we could go with making a rapid PCR machine out of a hair dryer. Before this decision, we took into consideration the danger of working with a hair dryer, failure due to uncertainty that the machine could be effectively controlled, and, on top of that, having less time to work on it. Nevertheless, we took the risk and are pleased to show you the results of our efforts—the creation of C.H.I.P.
