Difference between revisions of "Team:UMaryland/Hardware"

 
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<p style="font-size:64px"><u><b>CHIP: UMD's homemade PCR</b></u></style>
 
<p style="font-size:64px"><u><b>CHIP: UMD's homemade PCR</b></u></style>
 
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<h1><b>CHIP: Cheap Homemade Innovative PCR</b></h1>
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<h1><b>C.H.I.P: Cheap Homemade Innovative PCR</b></h1>
 
    
 
    
<p>Our first design for CHIP and employed, in many respects, a more conventional PCR design. CHIP utilized two peltier units below an aluminium heating block to heat the PCR tubes sitting inside the block. We used a temperature sensor to detect the temperature of the wells in which the PCR tubes were housed. The sensor then reported back to the Arduino unit, which regulated the energy flow to the peltier units, thereby heating and cooling the block and the tubes, and close the control loop. However our first design for CHIP proved to be unoriginal, expensive and inefficient. The design was conventional which in itself did not pose an issue, however, since these parts were generally not easily accessible to the general public we saw a problem going forward with this design. In addition although the price of the first PCR prototype was relatively inexpensive in contrast to laboratory grade PCR machines the price still ranged in the hundreds of dollars. The largest issue with our design was the inefficiency in the hardware; we found that the peltier units were not able to cycle fast enough. The unit would take a couple minutes to rise to 95 degrees. After considering all of these issues we began a redesign of CHIP to better suit the needs of the do it yourself market. </p>
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<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>
 
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<p>  Our second thermocycler design, was mostly made out of a salvaged hair dryer. We came about this idea when we found that CHIP was not ramping up to the desired temperatures fast enough. Because of this problem, we looked to other options for heating the machine and 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 degrees Celsius for PCR—in a few seconds. We then made a decision to pause construction of CHIP in order to see how successful we could be at making a rapid PCR machine out of a hair dryer. We knew that working on the hair dryer would be much more dangerous and was risk since at the time we were unsure if the machine could be controlled to effectively cycle and amplify DNA.   
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<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.   
  
 
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<h1><b>CHIP's Design</b></h1>
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<h1><b>C.H.I.P.'s Design</b></h1>
 
    
 
    
 
<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.  
 
<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.  
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  <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.
 
  <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.
 
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<h1><b>Problems and Current issues </b></h1>
 
<h1><b>Problems and Current issues </b></h1>
 
    
 
    
<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.  
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<p> We have had one successful amplification with our machine however we understand that repeatability is a vital component of all lab work and currently we are attempting to make our device repeatable. From our early days of testing we found that peltier units were not powerful enough to enable PCR tube to reach 95 degrees. Although conventional PCR machines use these units frequently they are often specialized and tailored made to perform PCR. With this tailoring comes a high price tag that does not suit the DIY market, and so we found a solution in the form of a hairdryer. The fan and heating element of a hairdryer provide a control scheme that enables for cycling of temperature rapidly and accurately and they are relatively inexpensive. We have found that developing a housing for the PCR tubes and enabling even heat distribution is challenging. We often have found that our temperature sensor and the pcr reaction tube are not at the same temperature and degree of difference is a delta of over 10 degrees celsius. We are currently working of milling a block of aluminum with better and more consistent heat transfer properties, and modeling the heat transfer within the can. Our ambition is that this will enable better control of temperature within the device.        
 
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Latest revision as of 04:20, 18 September 2015