[mems-talk] fluorescent microspheres getting stuck to PDMS channels.

[Matthew Davies]

I observed exactly the opposite, PS beads binding to glass rather than  
PDMS.  I was told that the beads would bind preferentially to a  
hydrophilic surface.  Go figure.

If its purely increasing the hydrophilicity of the PDMS that you're  after.
Either 1. Try running buffer through asap after bonding to the glass  
and  keeping it running though until you do your experiments	or
2. Running a reasonably strong ionic solution (NaOH has been  
recommended) through the channels BRIEFLY before you do your  
experiment.  Strong NaOH will turn your channels opaque if run through  
for too long (no idea of time, just info from a colleagues  
observations).

The idea is that PDMS' hydrophobicity is changeable and if a polar  
solution is in contact with the PDMS then the surface properties of  
PDMS will change.  I have observed this myself, but have not  
quantified so unfortunately cannot give more of a hint.

Oh one other way is to treat the PDMS with a polar group terminated  
silane.  If reacted with rather than adsorbed onto the surface, the  
silane should be relatively permanent (though it may still exhibit  
some transient decrease in polarity as it 'folds' back into the bulk).

Sorry I couldn't be more specific, but hope this helps.

Dr Matt Davies
Research Assistant
Science & Technology Research Institute
University of Hertfordshire
College Lane
HATFIELD	AL10 9AB
UK

e : m.davies at herts.ac.uk