Humidity is Affecting PDMS-pncSi Bonding

ByMike H

A few weeks ago Dave dropped of a humidity monitor for the third floor equipment room. Since then I have been recording the humidity every time I run a UV Ozone process for PDMS-glass or PDMS-pncSi bonding and there seems to be a correlation between the two.

Over the last week there seems to be a noticeable relation between humidity and bonding efficiency. Early this week and towards the end of last week the humidity was in the mid 40s and low 50s and we were getting successful bonding. Since then the humidity has slowly climbed to the high 50s and low 60s and  as a result our bonding  efficiency has greatly decreased (we have had 0% bonding over the past three days).

The plot above shows the relationship over the past week; the last three points 56,59, and 60 all have a bonding efficiency of 0%. A thing to note, the low efficiency of the date with a humidity of 49% is because I forgot to do an ethanol clean of the membranes prior to UV Ozone bonding. The failure to clean the membranes properly has already been shown to reduce bonding efficiency.

Most likely, there is not such a drastic cutoff where bonding will and will not occur with respect to humidity but I do think that there is a correlation.

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4 Comments

  1. Try heating the ozone cleaner stage > 100 C to drive off water vapor. I noticed that in the protocol you’re not heating the stage at all… is there a reason for this?

    Check your tags…

  2. The effect of humidity on PDMS is a well known consequence.
    Here’s a link to a microfluidic paper that goes into some vague detail about the effect…this paper might also give you a few more options to consider in fabricating your device:
    http://www.iop.org/EJ/article/0957-4484/16/4/023/nano5_4_023.pdf?request-id=7e8ffbfe-1181-4fc8-bf81-f2882e3874f2

    If the link doesn’t activate let me know and I’ll send you the paper. I have an entire collection of major microfluidic articles as well, if you’re interested.

  3. I think the PDMS ozone treatment should be done at a minimum of 100C, but you may want to try 75C, 100C, and 125C. Make sure it’s sitting on a glass slide or something, just in case something funny happens.

    Actually the bonding process should also be done in a dry oven at an elevated temperature. It will also accelerate the process..

  4. Thanks, I will try to run an ozone treatment today at 100C and try to have results posted for the meeting tomorrow.

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