Hi,

Has anyone doing microfluidics work for cell culture started having problems recently with getting their Sylgard 184 PDMS to reliably and permanently bond to the glass substrate? We have tried replacing our PDMS elastomer base and curing agent recently but this has not fixed our problem. We have also tried using 10% less curing agent which didn’t help either.

Briefly our protocol involves the initial bake at 60 degrees C for 1.5 hours, cutting out chips the next day then cleaning the PDMS surface with adhesive tape, cleaning the glass surface with 70% ethanol and a blast of nitrogen, plasma treatment for 30 seconds at 50% power/~15W (Zepto ONE, Diener Electronic plasma cleaner), and then sticking the surfaces together. Final annealing overnight at 60 degrees C before checking my chips for any bonding issues.

Normally when I have improperly bonded chips it’s immediately obvious and I’d see a portion of the bonded PDMS stuck onto the glass. Recently I’ve noticed that too many of the chips come off the glass cleanly, leaving no residual PDMS. I also sometimes find that a chip may be properly bonded but then it comes undone at a much later stage. All this leads me to think that the bonding is no longer permanent like it should be. I’d appreciate any feedback or advice, or if anyone else has noticed this and what may have worked for you if you did. Thanks very much in advance!