I make PDMS for microfluidic devices. I use Sylgard 184 in the ratio 1:10 and bake it for 3 hours at about 80 ° C. When I remove the mold PDMS previously done in SU-8 some regions are sticky like is not curing properly.
Anyone have an idea why this is happening?
Thanks.
Make sure you are mixing the PDMS base and curing agent very well. If you are using something like the Thinky AR-100, make sure the cup is spinning in the rotor. We have had ours get locked up from PDMS spills that don't get properly cleaned up and the way we usually notice it has happened is that someone has exactly your complaint about their PDMS. Back in the days when we mixed it with a fork, we mixed until the bubbles made the PDMS pearly white. After the degas, it would be mixed very well.
Ron Reiserer highlights the key consideration.
The only thing I would ask is the curing process. What is the mould material? How do you apply the temperature oven, fan-assisted oven, hot plate, etc.
It can be useful to place the mould on something (preheated) with a high heat capacity (like a metal block). Spinner chucks can be useful for this purpose.
Hi Maiara
you should mix the ratio very well (using a fork is highly recommended) and make sure to degass it very well. I am just wondering about the negative template with SU-8. Have you done that using a PMMA or silicon? If your negative template has also done using a PDMS, you should do a silination step first and then cure your PDMS liquid. If you haven’t done the salination and treatment with plasma, your final PDMS device will stick with the template
l hope this can help
Regards
Zaidon
Hello sir,
Ron Reiserer Zaidon T. Al-aqbi
I am trying to fabricate a thin film structure of PDMS on a glass slide. I diluted PDMS (0.5 gm) with 5 ml Hexane and add the hardener (0.05 gm) in it. Sonicated it for 5 min, spin-coated a thin film, and baked it for 2 days at 120 degrees but it is still sticky and didn't crosslink. I have tried this process 3 times but every time the results are the same.
Kindly guide me.
Thanks.
The curing agent for PDMS contains volatile components. This means that it can leave the bulk material without actually doing much cross linking when in a very thin film. Try curing at a lower temperature (around 60C for 5 hours or more) and put the substrate in a container with very little extra volume. I like to use something like an 8mm film tin.
Dear Aima Sameen Anjum , did Ron Reiserer 's recommendation of lowering the curing temperature solve the tackiness issue of your silicone?
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