BREAKING NEWS! The technique of UV Ozone Bonding is now complete

Hi all, the technique of UV Ozone bonding (of PDMS to glass, Si or pnc-Si) is now complete, serendipitously.

Hsin from Miller lab want to bond PDMS to glass, they tried plasma oxidation treatment and it worked.  The method is as followed: plasma oxidation treatment for 35 sec (which did not bond the sample, when it should), then oven-bake the sample to be bonded at 70 degree C for 10 min (which then did bond the sample; the motivation for this step arise from some suggestion in the literature).

Hsin wanted to try UV Ozone treatment too, maybe in part because i am trying to sell our instrument (the salesman way, not the actually selling, haha) , plus i told her i am curious to try her sample because it worked.

So we tried both her sample and mine (which serves as a control).  Basically, UV Ozone treat the sample for 10 min.  Somehow, her sample bonded pretty much 30 min after the treatment (could be shorter than that but we didn’t dare to try peeling it too early), while mine did not.  i am surprised because her sample did not need to sit overnight for complete bonding.  We tried the 10 min 70 degree C banking for my sample, it only bonded partially. 

So we discussed the differences in our sample preparation and there are many, but we isolated two potential factors: 1) where we cured our PDMS on (Hsin: glass, Henry: polystyrene petridish); and 2) which substrate we bond the PDMS to (Hsin: thick glass slide, Henry: glass coverslip or pnc-Si) .

So i tried

A) Hsin’s curing, Hsin’s substrate

B) Hsin’s curing, Henry’s substrate

C) Henry’s curing, Hsin’s substrate

D) Henry’s curing, Henry’s substrate

We know A) and C) worked, B) and D) did not.  CONCLUSION: it’s the substrate that we bond the PDMS to (in fact, Hsin’s thich glasss slide became yellow-tinted after the UV Ozone treatment, suggesting some sort of surface modification, which is not observed for our glass coverslip).

This finding is somewhat dicouraging, because in the future i will need to bond PDMS to our pnc-Si.  But then i decided to leave my sample in the oven for 30 min this time at 70 degree C.  THEN ALL OF THEM BONDED RIGHT AWAY! MUAHAHAHAHA!

***SO FINALIZED PROTOCOL: 10 min UV Ozone treatment, followed by 30 min 70 degree C bake.***

PS: Turns out people do baking after silanization treatment for the surface to be more hydroxyl group modified, i wonder what’s the mechanism behind it.  Please offer your 2 cents in the comment.  Thank you.

— Henry