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Homework Help: Question on Graphite Material

  1. Jul 15, 2014 #1
    Hi guys, I'm new to this forum and Im not so sure where to post my question..

    My first question, is graphite capable on detecting vibration?

    I'm currently doing my Final Year Project, trying to investigate on graphite compound. I using the graphite from the pencil lead and sketch it on a piece of paper, and trying to adapt the varies in resistivity behaviour upon any strain applied on the paper sheet.

    Somehow I found that the graphite resistance will keep changing overtime and it does not return to its original state.. And when there's vibration or strain apply on it, the changes of resistance is not much..So I wonder I had mistaken the overall structure or graphite just doesnt work in this way..

    Any expert here has any suggestion or advices for me...? I really need some help here..
  2. jcsd
  3. Jul 15, 2014 #2


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    Science Advisor
    Gold Member

    My first question would be: how are you measuring the resistance?
    My second is: how is the graphite applied to the paper?
    My third is: have you been tracking the relative humidity as the experiments are done?

    And a comment: pencil lead is not pure graphite; it is a finely ground mixture of graphite and clay.
    See http://science.howstuffworks.com/innovation/science-questions/question465.htm
  4. Jul 16, 2014 #3
    I measure the graphite by sketching a surface area of graphite using pencil lead on the paper, then protect it using tape to avoid the changes in its density due to relative humidity.
    Later on i try to apply strain or any vibration on my paper sheet to determine the graphite piezoresistive effect..
  5. Jul 16, 2014 #4


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    Staff: Mentor

    It is probably not stable in the long term, but apparently is the basis for making a usable sensor. You might be able to improve on your technique, take a look at what others have been doing: http://www.ncbi.nlm.nih.gov/pubmed/22778664
  6. Jul 16, 2014 #5
    I actually reviewed from here, and I try doing the same things..but it doesn't work well..my graphite resistance doesn't go back to its original state. Today I measure the value was 100k but tomorrow it was like 200k or more..
  7. Jul 17, 2014 #6


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    Staff: Mentor

    Yes, but maybe it is usable in the very short term? Say, 20 secs apart? Over longer periods the paper fibres may swell or contract with humidity changes, causing the overlying layers of carbon to change.

    I'm theorizing here, haven't investigated this myself.
  8. Jul 19, 2014 #7
    Hmm.. If i construct it in a way that the paper and graphite is protected from the relative humidity. Will it be possible to last longer? Lets say it's operating in a vacuum or what?
  9. Aug 14, 2014 #8
    I attachment my paper-based graphite sensor on a vibration plate, i found that it didn't not manage to achieve a stable outcome. Meanwhile, the reaction towards vibration was too random, and it takes very long time for the resistance in graphite to go back to its original value.. I wonder any expert here have solution for graphite sensor? more useful to detect vibration.
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