Bio-rad the samples to be within a certain

Bio-rad is a company that
produces thermal cyclers, also known as DNA cyclers, for use in stimulating the
polymerase chain in certain segments of DNA samples. The thermal cycler creates
an environment to facilitate the polymerase chain reaction to allow further
study of the DNA. Thermal cyclers are extremely useful tools for “detection and
diagnosis of infections and hereditary diseases, DNA cloning for sequencing,
and DNA profiling.” (DNA Cycler) Bio-rad contacted Aavid, the thermal division
of the Boyd corporation, to help design the thermally controlled environment of
the DNA cycler. Aavid was set the task of designing a fan and heatsink
combination to ensure the precise thermal requirements were met.

           

            The design of the thermal cycler was constrained by the
need for the samples to have no more than +/- 0.5C variation between them. Aavid
used a fan and a heatsink setup to achieve these results. They decided to use
components manufactured for electronics because of their mass production
leading to low costs and simplicity. The team at Aavid created an
airflow-thermal simulation model to test out the different combinations and
positions of the fan and heatsink. Next, they created a prototype of the
leading design to provide real-world data to plug back into the airflow-thermal
simulation model. Another aspect of the design that they came up with was the
removal of two side heaters from the design. They were able to achieve this by
placing insulating polyurethane foam at key locations to keep the samples at
the same temperature. The thermal cycler has been in use for several years
following Aavid’s involvement. There have been no problems with the design and
it has been a success.

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            The driving requirement for the DNA cycler was the
requirement for the samples to be within a certain variance of each other. This
constraint came from the use of the product. The samples’ temperature needs to
be reliably controlled between samples to maintain repeatability. The biggest
decision in the case study was the number and placement of the fans and
heatsinks. This was achieved through computational and real-world testing to
determine the optimal configuration. The biggest challenge overcome in the
design was the task to remove the two side heaters and maintain control of the
temperatures. This design was a success because it met the clients’ needs, was
cost effective, easy to produce, and has continued to work for many years. A
big lesson to learn for engineering students is the iterative process that real
design work follows. Similar to the point discussed in the lecture about
repeating through the steps to find the optimal design, Aavid went through a
number of airflow-thermal simulation model configurations, created a real-world
mockup, and ran it through the model again with new information.