I want to make a hydrophobic microfluidic device, I plasma bonded the device on a PDMS slab. Since I used plasma treatment, I wanted to know how long will it take for PDMS to lose hydrophilicity.
Hydrophobic recovery (Hydrophilic loss) happens over about 48 hours but the rate may be modified by factors such as humidity and if you keep the treated surface wet, you can maintain the hydrophilic surface for weeks. Recovery rate and completeness of recovery are also dependent on treatment time and power.
Hydrophobic recovery (Hydrophilic loss) happens over about 48 hours but the rate may be modified by factors such as humidity and if you keep the treated surface wet, you can maintain the hydrophilic surface for weeks. Recovery rate and completeness of recovery are also dependent on treatment time and power.
Same experience as Ron Reiserer (just under 48 h).
Interesting to learn that the hydrophilicity can be maintained for weeks by keeping it wet. Ron, do you looked at whether the ionic strength / pH of the solution makes a big difference there?
Jules.
Usually, if you need an hydrophilic surface, it is possible to use your chip for a couple of hours to one day, after the hydrophilicity might be too low to perform your experiments. The hydrophilicity can be preserved for longer times by keeping the channels in water or ethanol.
For more information about PDMS, do not hesitate to have a look at this review: https://www.elveflow.com/microfluidic-tutorials/microfluidic-reviews-and-tutorials/the-poly-di-methyl-siloxane-pdms-and-microfluidics/
We have always used sterile ultra-pure water. We have done no further testing or optimization.
In addition to what Ron mentioned, temperature is a factor. Storing wet and at low temperature maintains hydrophilicity longer. If you want to recover hydrophobicity faster keep the sample on a hotplate for several hours.
Hi
I the PDMS chip which is bonded on a glass slide on the hotplate at 80 °C for 20 min right after bonding. Then I fill the channels with oil before doing experiment. I have good hydrophobic chip doing this way.
Ron Reiserer Hi, Ron. Thanks for sharing! After I put my whole PDMS chips in water for storage, I find the chips will look blur. Heating the chips will make it clear again, but will make it hydrophobic. Did you also see this phenomenon?
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