Development of a Oxygen Sensor for Marine ... - DTU Nanotech

Chapter 4
System Design
The sensor layout is one of the more essential parts of the project, as the
design and general setup will be the deciding factor, in how well the sensor
will work. At such at least one design should be made that is reasonably
safe, which based on the general theory should work.
In this chapter the thoughts and ideas, concerning why the first designs of
the sensor(s) looks as they do, are given and explained.
4.1 General Design
Based on a previous project by Anders Hyldg˚ard [34], an ’O’-ring based
design was decided on, this was done in part to take advantage of the already
existing packaging scheme 1 . The setup uses an ’O’-ring as pressure sealing,
which leaves the active part of the sensor exposed, while protecting the rest
of the chip from the corrosive effects of seawater[35]. Of course care still has
to be taken, to ensure that it is tightly sealed, since even a small roughness
on the surface of the chip might allow seawater to seep through. Furthermore
a lot of the clean room steps from that project can be duplicated to create
the various layers in this design.
Making the sensor circular however presents other problems, as the sensor
needs a membrane covering it as mentioned in a Chapter 3, so that only
oxygen diffusing through the membrane is measured, as well as an electrolyte.
This in itself may not seem like a major obstacle, though given that the
membrane (Siloprene) is liquid to begin with, it needs a small ’container’
1 See the Packaging section for more info on this
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