<h1><b>C.H.I.P: Cheap Homemade Innovative PCR</b></h1>

<p> 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. </p>

<p>  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. 

<p>The design of CHIP started when we bought a hairdryer in the hopes of using the heating unit as part of our first PCR machine. However, as we were dismantling and testing the hairdryer, it became apparent to us that the heating system inside the hairdryer could reach the necessary temperatures independent of the peltier units already in use. With this in mind, we began working out how to wire the hairdryer so that we could regulate the heating unit and the fan separately.  

After a lot of soldering and reworking the internal safety measures inside the hairdryer, we were able to wire the system so that we could turn the heat on and off while running the fan continuously. Using autoclave tape, we secured a sheet of aluminium foil to the top of the heating unit of the hairdryer. The outer casing of the hairdryer had been removed. We placed a heat sensor inside the tin to measure the temperature of the air inside the machine.  By wiring the heat sensor to the arduino we were able to receive input/feedback from the sensor and adjust heating of the device to maintain our desired setpoints. We were able to regulate the heat of the machine and CHIP now thermocycled.  

  <p>After construction of the can based cover we tried PCR once more and still found that the reaction did not occur. We assumed that the heat sensor might have been an issue,; the sensor was exposed to the convected air and was relaying information about the air temperature instead of the temperature inside of the PCR tubes. This meant that our feedback system was not accurately responding and controlling the temperature inside of the PCR tubes. Assuming the temperatures inside the machine were not representative of the temperatures inside the PCR tubes, we put the heat sensor inside a PCR tube with mineral oil and placed this inside one of the holes. We ran another PCR reaction, ran the products on a gel and saw a large band of the correct size, indicating that CHIP worked.